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Review

The Effect of Polyploidisation on the Physiological Parameters, Biochemical Profile, and Tolerance to Abiotic and Biotic Stresses of Plants

by
Marta Koziara-Ciupa
and
Anna Trojak-Goluch
*
Department of Biotechnology and Plant Breeding, Institute of Soil Science and Plant Cultivation—State Research Institute, 24-100 Puławy, Poland
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(8), 1918; https://doi.org/10.3390/agronomy15081918
Submission received: 25 June 2025 / Revised: 1 August 2025 / Accepted: 6 August 2025 / Published: 8 August 2025

Abstract

Polyploidisation is a very common phenomenon in the plant kingdom and plays a key role in plant evolution and breeding. It promotes speciation and the extension of biodiversity. It is estimated that approximately 47% of flowering plant species are polyploids, derived from two or more diploid ancestral species. In natural populations, the predominant methods of whole-genome multiplication are somatic cell polyploidisation, meiotic cell polyploidisation, or endoreduplication. The formation and maintenance of polyploidy is accompanied by a series of epigenetic and gene expression changes, leading to alterations in the structural, physiological, and biochemical characteristics of polyploids relative to diploids. This article provides information on the mechanisms of formation of natural and synthetic polyploids. It presents a number of examples of the effects of polyploidisation on the composition and content of secondary metabolites of polyploids, providing evidence of the importance of the phenomenon in plant adaptation to the environment, improvement of wild species, and crops. It aims to gather and systematise knowledge on the effects of polyploidisation on plant physiological traits, including stomatal conductance (Gs), transpiration rate (Tr), light saturation point (LSP), as well as the most important photosynthetic parameters determining biomass accumulation. The text also presents the latest findings on the adaptation of polyploids to biotic and abiotic stresses and explains the basic mechanisms of epigenetic changes determining resistance to selected stress factors.

1. Introduction

Polyploidy, the multiplication of the total number of chromosomes naturally present in cells, is a widespread phenomenon in nature. It plays a significant role in the evolution of plants and animals, as it promotes the formation of new species. It can occur in nature either spontaneously, influenced by environmental factors, or artificially, through the use of antimitotic compounds that disrupt the process of cell division [1]. Polyploidy is indisputably associated with the processes of cell and tissue differentiation, and organisms resulting from this process are referred to as polyploids [2,3]. Polyploid organisms that contain more than two sets of homologous chromosomes (i.e., chromosomes from a single species) are known as autopolyploids [4]. The most common autopolyploids found in nature are autotetraploids (4n), containing four sets of chromosomes, or autohexaploids (6n) and autooctaploids (8n), which contain six and eight genomes, respectively [1,2,3]. Examples of naturally occurring autotetraploids include coffee [5], leek [6], banana [7], and sugarcane [8]. When two or more sets of homeologous chromosomes (i.e., from different parental species) are multiplied in the cell nucleus, the result is an allopolyploid. The distinction between allotriploids, allotetraploids, allohexaploids, etc., depends on the number of multiplied genomes [2,9]. Examples of allopolyploids that have naturally formed include species such as tobacco (Nicotiana tabacum L.), common cotton (Gossypium hirsutum L.), and giant miscanthus (Miscanthus × giganteus Greef et Deu.) [10,11,12].
The presence of polyploids, including both auto- and allopolyploids, in the plant kingdom has significant evolutionary and ecological consequences. It has been shown to promote speciation, biodiversity preservation, and plant adaptation to changing environmental conditions [3,4,13]. In polyploid organisms, duplicated chromosomes undergo changes in their number and undergo rearrangement, a process that remodels genomes [14,15]. Some duplicated genes undergo pseudogenization, whereby their functions are lost [16]. In contrast, other duplicated genes may evolve to acquire new or slightly modified functions in a process known as neofunctionalization [4,17]. Changes in the function of duplicated genes can increase phenotypic plasticity in polyploids compared to their diploid ancestors. An increase in the number of dominant alleles and a decrease in the influence of recessive alleles is also frequently observed [18,19]. This phenomenon has been shown to promote new, potentially beneficial variations in response to environmental factors. For instance, increased resistance to low temperatures [20,21] and increased tolerance to salinity and drought [22] have been observed as a result. Chao et al. [23] posited that naturally occurring tetraploid Arabidopsis thaliana (L.) Heynh. plants exhibit enhanced salinity tolerance compared to diploids. Furthermore, watermelon plants that have been grafted onto tetraploid rootstocks exhibit a greater degree of salt stress tolerance than those with a diploid genetic composition [24]. Polyploids have an increased gene dosage compared to diploids and differences in gene sequence and regulatory elements. This results in a number of morphological, physiological, and biochemical changes [25]. Polyploids are generally known to produce somatic cells that are larger than those of diploid plants. Increased cell size and higher cytoplasm content are often linked to higher crop yields. This phenomenon, known as the “giga effect” (Figure 1 and Figure 2), is becoming increasingly important in the context of a changing climate, characterised by increased biotic and abiotic stresses, which lead to a global decline in crop production [20]. As the level of plant ploidy increases, so do the net photosynthetic intensity index (Pn) and stomatal conductance (Gs) increase, ultimately resulting in better photosynthetic efficiency [26]. Furthermore, the existing literature indicates that the duplication of genetic material and gene regulatory elements results in changes to the expression of genes that determine biochemical traits in plants [27]. Le et al. [28] indicate that polyploidisation is an efficient method for inducing biochemical modifications, including an increase in ginsenosides in Panax ginseng C. A. Meyer. Conant et al. [29] and Gaynor et al. [30] have documented that the duplication of genetic material contributes to a partial reduction in gene activity due to gene-specific or regional gene silencing. This then causes a decline in the production of specific bioactive substances [29,30]. Therefore, plant polyploidisation provides the potential for increased resilience against biotic and abiotic stressors.

2. Review Methodology

This paper examines the phenomenon of ploidy in cultivated field crops, including medicinal plants and spices. The effects of polyploidisation on plant genomes, along with morphological and anatomical traits, have been extensively researched. Numerous publications detail the plant’s growth habit and modifications in anatomical and morphological structures of polyploids compared to diploids [31,32]. The basis for conducting this review is the ongoing development of research that validates perspectives on the alterations in the functionality of duplicated genes and their part in enhancing plant resilience to diverse forms of stress. This is particularly important in the context of intensified climate change, which often leads to a decline in plant yields, the spread of invasive species, and the loss of biodiversity. Duplicated genomes provide polyploids with increased adaptability to climate change and the ability to colonise new ecosystems.
This review also presents an overview of the literature on methods of polyploid induction and the relationship between genome size and the intensity of physiological processes, including transpiration, photosynthetic efficiency, and water use efficiency. The challenge for scientists is to enhance the efficiency of plant biomass production while maintaining the quality of agricultural products.
Furthermore, the impact of polyploidisation on the content of secondary metabolites in plants is also being verified. As demonstrated by recent studies, genome duplication has been shown to have a significant impact on the biochemical profile of plants. In a number of species, it has been shown to be beneficial, increasing the production of specialised secondary metabolites. However, polyploids of species in which there is a decrease in desirable secondary metabolites still pose a significant challenge for scientists and plant breeders.
The added value of this review article is its comprehensive analysis of the response of polyploids to various stress conditions. Polyploids exhibit a variety of responses to stress, both abiotic (e.g., drought, low temperature) and biotic (e.g., infection, pest infestation). On the one hand, polyploids are often more tolerant to stress than their diploid counterparts. However, it should be noted that individuals in these groups may exhibit heightened sensitivity to specific stress factors. The review indicates that responses are influenced by various factors, including species, ploidy level, and the nature of the stress.
The article was prepared using a semi-systematic literature review method. The literature used in the review was obtained from the Scopus, Web of Science, ResearchGate, EDS and J-Stage databases. The majority of these reports present research findings from the past decade. Nevertheless, some sections, particularly those addressing polyploid induction methods and the reaction of polyploids to biotic stresses, additionally provide citations from earlier research.

3. Methods of Plant Polyploidisation

In nature, the multiplication of chromosomes can occur either spontaneously or as a result of antimitotic compounds or other factors that disrupt the course of meiosis or mitosis.

3.1. Meiotic Polyploidisation

Disruptions to the process of meiosis result in the formation of unreduced gametes (2n), which makes it possible to generate polyploid organisms. The fusion of gametes (2n) of the same species leads to the formation of autopolyploids, while the fusion of unreduced gametes from different species gives rise to allopolyploids [33]. Fertilization of an egg cell by a sperm cell with an unreduced number of chromosomes (2n) results in a tetraploid being created. Conversely, combining an egg cell (2n) with a sperm cell that has a reduced number of chromosomes (n) results in a triploid organism. Under natural conditions, the production of unreduced gametes is primarily favoured by internal factors, such as the life cycle of plants. Consequently, perennial species are much more likely to produce gametes (2n) than annual species. Furthermore, a species’ mode of reproduction, including self-pollination, promotes the production of polyploid gametes [34]. Spontaneous polyploid pollen grains and naturally occurring triploids have been observed in perennial trees such as Acacia dealbata Link., Quercus petraea (Matt.) Liebl., and Quercus robur L. [35,36]. A number of polyploids have also been documented as a consequence of interspecific hybridisation. Examples include the hybridisation of N. glauca Graham and N. langsdorffii Weinm., N. tabacum L. and N. glauca Graham, Gossypium hirsutum L. and G. herbaceum L., and Hibiscus syriacus L. and H. paramutabilis L. H. Bailey, which produced fertile, polyploid interspecific hybrids [10,37,38,39]. In addition to internal factors, external factors such as heat shock, drought, nitrous oxide treatment, and plant malnutrition during flowering are important stimulators of gamete (2n) production [34,40]. The frequency of polyploid gametes has been reported to increase as a result of the treatment of female flower buds of the Populus adenopoda Maxim at high temperatures (38–44 °C) [41], as well as buds of hybrids of the Populus pseudo-simonii Kitag. × P. nigra (L.) ‘Zheyin3#’ [42]. A 48-h treatment of flower buds of diploid, sterile Lilium cultivars with N2O under 600 kPa pressure was found to be equally effective in producing 2n gametes [43]. A highly efficacious technique for modifying the ploidy level of plants is controlled interploid crossing, specifically 2× × 3×, 3× × 4× and 2× × 4× combinations [44,45]. The hybridisation of the diploid (2×) species of N. glutinosa L. and N. tabacum has resulted in the synthetic polyploid species of N. digluta [46]. Crossing tetraploid (4×) and diploid (2×) forms of Solanum tuberosum L. has been shown to stimulate the production of male gametes (2n) at a level of approximately 22%, resulting in triploid potato families [47]. This technique has also been used to breed many useful triploid hop cultivars [48]. Studies on the hybridisation of diploid Miscanthus sinensis Andersson and tetraploid M. sacchariflorus (Maxim.) Hack. led to the formation of the triploid species M. × giganteus [49]. The effectiveness of genome multiplication through interploid crosses is significantly contingent upon the specific genotype or species selected, as demonstrated through studies involving M. giganteus (6×) and M. sinensis (2×) [50].

3.2. Mitotic Polyploidisation

A number of methods are available to duplicate the number of chromosomes in somatic cells. Mitotic polyploidisation is a process that can occur spontaneously, often resulting in the doubling of genetic material in meristematic cells. Another technique involves the controlled induction of chromosome disjunctions in the anaphase of mitosis to duplicate genetic material. The process involves applying temperature shocks, X-rays, or mitotic poisons, including colchicine, oryzalin, trifluralin, and methyl amiprophos [20,25,51,52]. These antimitotic compounds can be applied to various plant materials, such as germinating seeds, root growth cones, young seedlings, buds and shoot tips, callus, as well as nodal segments [51,52,53]. Colchicine is the most widely used agent to induce polyploidy [21]. This poisonous alkaloid is easily soluble in chloroform and alcohol. Extracted from the bulbs and seeds of autumn winterberry (Colchicum autumnale L.), it inhibits the polymerisation of the microtubules in the karyokinetic spindle, thereby preventing mitosis and the separation of chromatids into progeny cells [21,54]. Consequently, tissues, shoots, or entire plants are produced that have a doubled number of chromosomes in their somatic cells when compared to the original plant [21,55]. An alternative to colchicine might be oryzalin. This pre-emergence herbicide has been successfully used to produce polyploids of economically important species such as Miscanthus sinensis [56], Agastache foeniculum (Pursh) Kuntze [57], Cannabis sativa L. [58], and Stevia rebaudiana Bert. [59]. Antimitotic compounds are used in vivo and in many in vitro experiments for polyploidisation [21,55,60].
Dixit and Chaudhary [61] obtained tetraploid garlic genotypes by treating stem discs with a 0.5% (w/v) colchicine solution. In contrast, Švécarová et al. [53] used different oryzalin application techniques to produce polyploids in hop (Humulus lupulus L.). The first method involved culturing nodal segments on an oryzalin medium at concentrations of 1.5 and 10 µM for a period of two weeks. The second method involved soaking nodal segments in a solution of 10 or 20 µM oryzalin for 24 or 48 h, respectively. Embryos treated with higher concentrations of trifluralin and colchicine exhibited higher levels of viability, and the resulting polyploid plants were used for further breeding work [53]. In contrast, tetraploid fenugreek (Trigonella foenum-graecum L.) plants were obtained by placing isolated embryos on an MS medium enriched with various concentrations of either colchicine (0, 75, 150, 300, or 600 µM) or trifluralin (0, 125, 250, or 500 µM). The researchers found that prolonged exposure to 500 µM trifluralin resulted in significantly lower mortality in polyploid plants than exposure to 600 µM colchicine [62]. Dwiati et al. [63] used oryzalin at concentrations ranging from 0 to 100 µM to induce polyploid Vanda limbata Blume plants in vitro. According to the authors, the initial morphological changes indicating polyploidisation were visible at the lowest concentration of oryzalin. However, the most effective concentration for inducing polyploidy was found to be 100 µM oryzalin. Treatment of seedlings with oryzalin at higher concentrations resulted in increased survival rates after eight weeks, alongside enhanced shoot proliferation and wider leaf development compared to the control seedlings. Dhooghe et al. [64] induced polyploidy in vitro in Helleborus niger L., H. orientalis Lam., and H. nigercors L. by applying various mitotic poisons to young hellebore shoots. The poisons used were colchicine, oryzalin, and trifluralin. Cytometric analysis of the obtained plants showed that the efficiency of polyploidisation depended on both the species used and the type of mitotic poison applied and its concentration. Trifluralin at 10 µM was the most effective at inducing tetraploids, whereas colchicine at 100 µM was completely ineffective. Of the three hellebore species, H. niger was found to be the most susceptible to polyploidisation. According to the literature presented, mitotic poisons are the most commonly used method for the artificial in vitro induction of polyploids. Polyploid plants resulting from the use of very high concentrations of antimitotic poisons have a lower survival rate. Additionally, prolonged exposure to a particular antimitotic agent has been observed to result in a decline in the survival rate of induced polyploids. More effective polyploid induction is observed at lower concentrations of antimitotic poisons and shorter exposure times.

4. The Effect of Polyploidisation on the Content of Plant Secondary Metabolites

In response to changes in ploidy level and increased gene copy number in plants, many genes encoding proteins in metabolic pathways are activated. This process subsequently affects the composition, quantity, and proportions of secondary metabolites [15]. Secondary metabolites are organic compounds that play an important role in how plants interact with their environment [1]. To date, over 50,000 secondary metabolites have been identified in plants [65], with some acting as attractants or repellents to protect against biotic agents such as herbivores and pathogens [66]. It is important to note that others can initiate flowering and fruit setting, and can enable perennial plant growth. Comparisons of the metabolic profiles of diploids of Arabidopsis thaliana (L.) Heynh. [67] and Papaver somniferum L. [68], as well as artificially produced polyploids of these species, revealed significant differences in the concentrations of secondary metabolites associated with tricarboxylic acid (TCA) and γ-aminobutyric acid (GABA) cycling [67], as well as morphine and codeine production [68]. Given the extensive existing literature on this topic, the manuscript focuses on the effect of polyploidisation on the chemical composition of plants, with a particular emphasis on alkaloids, essential oils, flavonoids, and bitter acids (Figure 3).

4.1. Alkaloids

Alkaloids are a group of plant-derived compounds containing one or more nitrogen atoms in a heterocyclic ring [65]. These substances can account for up to 10% of a plant’s composition, with accumulation mostly occurring in leaves, flowers, or roots. Alkaloids are primarily produced by poppy plants, broad beans, buttercups, and certain types of lower plants, such as forbs and horsetails [69]. The characteristics of these compounds include a bitter taste and they play a role in the germination of plants and their protection from predators, particularly herbivores and microorganisms. Polyploid plants have the capacity to synthesise significant quantities of alkaloids, including scopolamine, hyoscine, vindoline, morphine, and codeine, which are found in medicinal plants [68,70,71].
Xing et al. [72] used polyploidisation to generate tetraploid lines of Catharanthus roseus (L.) G. Don which exhibited elevated alkaloid levels. In comparison with diploids, tetraploid leaves were found to contain higher levels of vindoline, catharanthine, and vinblastine, with respective increases of 130.9, 188.6, and 122.6%. Further qRT-PCR studies demonstrated that this was due to increased expression of seven out of ten genes that determine the production of enzymes in the terpenoid biosynthesis pathway, including Orca3, Tdc, G10h, Sls, Str, Dat, and Prx1. In addition, Nourozi et al. [73] conducted a comparative analysis of diploids and tetraploids of C. roseus and observed a substantial increase in the levels of vincristine, vinblastine, catharanthine, and vindoline of 82.2, 80.9, 44.3, and 71.2%, respectively, in the Red Really cultivar. A similar increase was noted in the Polka Dot cultivar, with respective increases of 64.7%, 31.0%, 48.2%, and 95.3%. In another study, Mishra et al. [68] demonstrated that tetraploids of poppy (Papaver somniferum L.) produced 47.7% more morphine and less thebaine and codeine when treated with a 0.4% colchicine solution than diploids. This is due to the activation of the expression of genes involved in the biosynthesis of morphinanes resulting from genome polyploidisation. As stated in the study by Berkov and Philipov [70], a comparative analysis was conducted of the alkaloid production and accumulation in the roots and leaves of diploid and tetraploid Datura stramonium L. plants. The study revealed that tetraploids produced higher levels of alkaloids in both roots and leaves than diploids did. For example, the hyoscyamine content of tetraploid roots was 1.24-fold higher than that of diploids and the scopolamine content was 1.35-fold higher. The increased alkaloid production in the roots of tetraploids resulted in significantly higher levels of the aforementioned alkaloids being found in the leaves. Dehghan et al. [71] investigated the effect of ploidy level on alkaloid production in the leaves and hairy roots of Hyoscyamus muticus L. cultures maintained on B5 medium + 20 g·L−1 sucrose. The leaves of tetraploid plants produced three times more scopolamine and half as much hyoscyamine as their diploid counterparts. Furthermore, hairy root cultures of tetraploids were found to be an excellent source of scopolamine. However, the authors emphasise that the production of tropane alkaloids can be significantly modified by plant culture conditions, including the type of medium and carbon source, as well as the degree of ploidy of the plants. The highest concentrations of scopolamine (0.99 mg·g−1) and hyoscyamine (6.59 mg·g−1) were obtained in diploids cultured on an MS + 20 g·L−1 sucrose medium. Under the same conditions, tetraploids produced three times less scopolamine and 1.1 times less hyoscyamine. These examples support the hypothesis that polyploids are an excellent source of alkaloids, including those with therapeutic potential. Therefore, research should be undertaken to induce polyploids that produce greater quantities of health-promoting alkaloids.

4.2. Essential Oils

Essential oils represent a diverse group of plant-derived products, characterised by a wide range of chemical compositions and a variety of properties. It has been demonstrated that mixtures of compounds possess antiviral, antibacterial, and antifungal activities. Furthermore, they have the potential to serve as therapeutic agents or adjuvants in pharmaceutical contexts, as well as being utilised as natural, biodegradable plant protection products [74]. Research has shown that the ploidy level of plants can affect the production of essential oils [1]. Das [75] concluded that almost a quarter of colchicine-induced tetraploid chamomile cultivars outperform their diploid progenitors with regard to essential oil content. As stated in the study by Shmeit et al. [74], essential oil production increased by 0.38% in vitro for Thymus vulgaris L. tetraploids when induced from nodal segments, in comparison to the production levels characteristic of diploids. Furthermore, a higher thymol and carvacrol content was found in the polyploids by 18.01% and 0.49%, respectively. In a related study, Navrátilová et al. [76] demonstrated that the doubled DNA content leads to alterations in the composition of essential oils extracted from field-grown tetraploids (TR15-22) of T. vulgaris. It is evident that genome polyploidisation has resulted in an increased proportion of biologically active compounds, including thymol, carvacrol, trans-caryophyllene, UN3, and UN4 (unknown terpenes), which have potent insecticidal properties. Research by Mohammadi et al. [77] provides valuable insights into the tetraploid characteristics of T. vulgaris. They showed an increased content of essential oils by 64.7% compared to that recorded in diploids, in addition to an increase of 40.9% in thymol content and 18.6% in carvacrol content. Compositionally modified tetraploid thyme essential oil was found to be more toxic to insect larvae feeding on thyme. In 2024, Gupta et al. [78] conducted a study to evaluate the antimicrobial, antioxidant, and anti-inflammatory properties of thyme essential oils extracted from tetraploid and diploid species of T. vulgaris. Polyploids demonstrated a 41.11% increase in essential oil production in comparison with the control diploids. Additionally, oryzalin-treated tetraploid Melissa officinalis L. demonstrated a 75% increase in essential oil yield compared to diploids [79]. Furthermore, a comparison of the essential oil chemistry of diploids and tetraploids of the species demonstrated an increase of 11.06% in geranial content and 9.49% in neral content in polyploids. Hop is an excellent source of many secondary metabolites, including terpenes, chalcones, polyphenols and essential oils [80]. The degree of ploidy in hop significantly affects morphological changes and the production levels of organic compounds, particularly those responsible for aroma [81,82]. Although tetraploids were found to have a lower total essential oil content than diploids, their composition was nevertheless dominated by valuable oils, such as humulene, limonene, caryophyllene, and farnesene [83].

4.3. Flavonoids

Flavonoids represent a significant group of secondary metabolites belonging to the polyphenol group. These substances are predominantly found in fruits and vegetables [84]. They are responsible for the colour and aroma of flowers, as well as for attracting pollinators. Thanks to their antioxidant, anti-inflammatory, and anticancer properties, flavonoids can protect plants from various biotic and abiotic stresses, thus playing a key role in acclimatising them to new environments [84].
Change in ploidy levels caused by mitotic poisons can effectively contribute to increased flavonoid production, particularly in medicinal plants such as rustica [85], mugwort [86], and sage [87]. Hassanzadeh et al. [88] studied colchicine-induced polyploids of sage (Salvia officinalis L.) and demonstrated favourable morphological and biochemical changes in tetraploids, including an increase of 21.9% and 24.4% in phenolic compound and flavonoid content, respectively, compared to diploids. However, no significant differences in total protein content were observed between the plants. In contrast, Kasmiyati et al. [86] investigated the effect of the polyploidisation of the genome of mugwort (Artemisia cina O. Berg) on the content of two primary flavonoids: kemferol and quercetin. The authors used just two diploid and two polyploid genotypes. It was demonstrated that the doubling of the number of chromosomes was accompanied by a significantly higher content of quercetin and kaempferol than in diploids. A subsequent study of a diploid (KJT) and polyploid (J) genotype of mugwort (A. cina), revealed slightly higher concentrations of quercetin and kaempferol. However, no significant differences were detected in the antibacterial activity of the two genotypes [89]. The doubling of the number of chromosomes in rustica (Galega officinalis L.) was also accompanied by an increase in the content of health-promoting compounds, including phenols, flavonoids, and galegine [85]. However, it should be noted that an increase in genomic DNA content does not necessarily result in a concomitant increase in the content of secondary metabolites [90]. A study found a range of secondary metabolites to be reduced in tetraploid plants of Mentha spiculata L., Digitalis purpurea L., Digitalis lanata Ehrh., and Trigonella foenum-graecum L., in comparison to their diploid counterparts [91].

4.4. Bitter Acids

Bitter acids, including alpha acids (humulone, cohumulone, and adhumulone) and beta acids (lupulone, colupulone, and adlupulone), are found in soft hop resins. These compounds are recognised as being responsible for the bitterness characteristic of hop in beer [92]. Changes in the DNA content of hop cells are also associated with changes in soft hop resin content. The alpha acids content in tetraploids was lower than that of the Sybilla control [83]. A two-year experiment comparing triploid and diploid hop populations revealed significant variation among individuals in this respect. Triploid genotypes with an alpha acid content of 5.71% d.w. were selected, exceeding the value characteristic of the initial diploid cultivar Sybilla. Genotypes with a significantly lower alpha acid content (3.84%) than the control were also selected [93].

5. The Effect of Polyploidy on Plant Physiological Traits and Photosynthetic Efficiency

In addition to influencing the rate of cell division and the production of secondary metabolites, altering the ploidy level of plants allows polyploids to adapt more efficiently to adverse environmental conditions and colonise newly accessible areas, unlike diploids. Recent research has revealed that polyploids exhibit morphological characteristics that modify plant physiological processes in plants. Compared with their diploid counterparts, they have a larger number of mesophyll cells and a smaller number of chloroplasts in palisade parenchyma cells [94,95]. Furthermore, the number and volume of chloroplasts, as well as chlorophyll content, have been shown to correlate positively with cell size [26]. It has been demonstrated that genome polyploidisation often leads to an increase in cell size, accompanied by a reduction in the number of cells per unit of leaf area [26]. Therefore, it has been hypothesised that the degree of ploidy in plants affects the intensity of photosynthesis per unit area by influencing leaf morphological parameters, including cell size and number per unit leaf area. Warner et al. [96] report that if the increase in photosynthetic efficiency per cell is proportionally greater than the decrease in cell number of per unit leaf area due to polyploidisation, the photosynthetic rate per unit leaf area may exceed that of diploids. Conversely, an increase in photosynthetic efficiency per cell, coupled with an increase in ploidy and a reduction in the number of cells per unit area due to larger cell sizes, can lead to the maintenance or slight decrease of the photosynthetic rate per unit of leaf area.

5.1. Lilium spp.

Cao et al. [97] conducted a study investigating the impact of polyploidisation on the photosynthetic processes of Lilium FO hybrids. They found that tetraploid plants exhibited a higher net photosynthetic rate (Pn) and maximum net photosynthetic rate (Pmax) than diploid plants under both natural conditions and conditions involving variations in light intensity and CO2 concentration. Furthermore, tetraploids exhibited a significantly higher light saturation point (LSP) and a lower light compensation point (LCP) than diploids, suggesting an enhanced capacity for light energy acquisition in tetraploid plants. A similar study evaluating the differences in the photosynthetic and transcriptomic indices between diploid and tetraploid barley cultivars was conducted by Chen et al. [98]. Under high-intensity light conditions, tetraploid barley exhibited increased net photosynthetic rates (Pn), along with increased stomatal conductance (Gs), transpiration rate (Tr), maximum net photosynthetic rates (Pmax), intercellular CO2 concentrations (Ci), light saturation points (LSP), maximum RuBP-saturated carboxylation rates (Vcmax), and maximum rates of electron transport (Jmax) (Figure 3). Additionally, transcriptomic analyses revealed that most of the 793 genes examined exhibited differential expression according to the ploidy level of the plants. As reported by Chen et al. [98], 580 of these genes showed higher expression in tetraploid barley than in diploid barley.

5.2. Melissa officinalis

A study conducted by Bharati et al. [79] on oryzalin-induced tetraploids of Melissa officinalis L. nodal segments showed significantly higher chlorophyll content (1.32 ± 0.07 mg·g−1 FW) than diploids (0.93 ± 0.05 mg·g−1 FW). In addition, the results showed that polyploid lemon balm had considerably higher photosystem II function index (PIabs) values and lower values of the photon flux absorbed by antenna dye molecules per active reaction centre (ABS/RC) values, in comparison to diploids. This finding suggests that polyploid lemon balm is more efficient at absorbing and utilising light energy in photosynthesis. The authors also point out that, unlike diploids, tetraploid genotypes are characterised by a linear electron flow (LEF) that is almost three times higher, particularly in the morning and afternoon. These results suggest that the conversion of light energy into electron transport across the thylakoid membrane in tetraploids may be more efficient, thereby enhancing photosynthetic activity.

5.3. Apple Tree

In addition, the relationship between genome polyploidisation and photosynthetic activity in apple trees was investigated, alongside plant physiological parameters [99]. The findings showed that this relationship varied according to cultivar. Tetraploids of two of the three varieties exhibited significantly higher transpiration rates (mmol H2O m−2s−1). However, the photosynthetic activity and maximum PSII quantum yield (Fv/Fm) in the tetraploids were similar to those observed in the diploids.

5.4. Triticum

Studies conducted by Hejnăk et al. [100] on various wheat species revealed that Triticum monococcum L. diploids exhibited significantly higher photosynthetic rates (Pn = 32.5 µmol CO2 m−2 s−1) than T. aestivum L. hexaploids of (Pn = 29.6 CO2 m−2 s−1) and T. durum Desf. tetraploids of (28.3 CO2 m−2 s−1).

5.5. Fragaria

A comparable situation was observed in species of the genus Fragaria from the Rosaceae family. As demonstrated in the study by Gao et al. [101], the diploid species Fragaria pentaphylla Losinsk. exhibited a considerably higher photosynthetic capacity than the tetraploid species F. moupinensis (Franch.) Cardot. This included higher net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr). Šmarda et al. [102] conducted a study on a broad spectrum of polyploids exposed to varying concentrations of atmospheric CO2 (200, 400, and 800 ppm). The study revealed that polyploids exhibited enhanced growth at low CO2 levels compared to diploids. Furthermore, they demonstrated that the increased genome of polyploids did not reduce the fraction of the epidermis formed by the stomata. This ultimately resulted in slightly higher stomatal conductance and photosynthetic rates at low CO2 concentrations than were recorded for diploids. As Gao et al. [101] previously observed, Fragaria polyploids exhibit superior photosynthetic efficiency and biomass production compared to diploids. Based on this information, it can be assumed that the photosynthetic response of polyploids varies depending on species, level of ploidy within species, cultivar, and plant growth conditions.

5.6. Phlox drummondii

There are many reports indicating morphological and physiological differences between diploids and polyploids, as well as presenting results obtained for artificially created polyploids. These are most often autopolyploid populations obtained immediately after polyploidisation. However, few reports address the photosynthetic rates of subsequent polyploid generations obtained through self-pollination. Vyas et al. [103] studied the effect of genome duplication on the photosynthetic parameters of two groups of Phlox drummondii Hook. autotetraploids: those obtained through multiple self-pollination (C11), and those resulting from genome duplication (C0). The study demonstrated that C11 plants exhibited a higher intercellular CO2 concentration, as well as significantly higher chlorophyll content and photosynthetic rates, than both diploids and C0 polyploids. This suggests that self-pollination stabilises the polyploid genome and improves physiological parameters in plants.

5.7. Oryza sativa

Polyploidisation is a widely used method in rice breeding. In recent years, studies on autotetraploid rice have primarily focused on characteristics such as photosynthesis, DNA methylation, agronomic traits, seed setting rate, and yield potential. Xiao et al. [104] investigated the impact of nitrogen (N) fertiliser management on the agronomic characteristics and physiological parameters of rice and found that autotetraploids exhibited a lower photosynthetic rate than diploids. However, Yang et al. [105] found that autotetraploid rice lines had higher chlorophyll content, a greater electron transport rate (Pn), and a higher photosynthetic capacity and light utilisation efficiency than diploid lines.

6. Response of Polyploids to Abiotic Stress

Abiotic stress is defined as the occurrence of an unfavourable physical environmental factor that triggers a series of physiological and metabolic reactions that negatively impact on plant growth and development [106]. Examples of abiotic stressors include water shortage (i.e., drought), salinity, extremely high or low temperatures, ultraviolet radiation, and nutrient deficiency. Abiotic stress factors are the most common cause of variation and decline in yield quality from year-to-year [107]. The effects of these factors on polyploid crop are not yet fully understood, but an increasing number of studies on the interaction between the genome and environmental stressors are improving our understanding of this relationship. Polyploids generally exhibit greater resilience to various abiotic stresses, such as low and high temperatures, water deficiency, and excess water and soil salinity, than diploids do [108,109]. Recent findings from the last ten years provide clear evidence that polyploidisation benefits plants’ ability to adapt to various abiotic stresses (Table 1).

6.1. Drought Stress

Drought stress is caused by insufficient water in the environment in which plants grow, resulting in an imbalance between transpiration and the amount of water that plants take up from the soil [125]. Due to the increasingly evident phenomenon of global climate warming, drought is becoming a more prevalent and significant environmental challenge. It is estimated that arid and semi-arid regions currently account for approximately 30% of the Earth’s total land area [126]. Soil water deficiency is an increasingly significant problem that can impacts plant growth and productivity. Therefore, drought represents a significant challenge for the global economy and food production. In response to drought, plants undergo a range of physiological, structural and biochemical changes, including the accumulation of polyamines, which perform a similar function to osmolytes [127]. Another important class of proteins that protect the structure of other proteins and cell membranes are LEA proteins (Late Embryogenesis Abundant proteins) [128]. In terms of stress tolerance, detoxification enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidases (POD) are particularly important due to their role in removing reactive oxygen species (ROS).
Polyploids are characterised by their enhanced ability to adapt to drought stress. Whole genome duplication (WGD) can lead to changes in leaf anatomy and stomatal dimensions. These alterations have been shown to modify the tissue water potential, transpiration rate, and stomatal conductance of Solanum betaceum Cav. during drought periods [129]. Diallo et al. [115] demonstrated that genome polyploidisation enhances the drought tolerance of Acacia senegal (L.) Willd., attributing this to a 54% increase in stomatal width and a 31% decrease in stomatal density compared to diploids. Furthermore, polyploids exposed to drought stress grew 28% taller and had a larger leaf area. Neotetraploids and tetraploids of the perennial herbaceous plant Chamerion angustifolium (L.) Schur are characterised by their larger stomata and increased xylem conduit size. However, no detectable differences were observed in terms of maximum stomatal conductance and gas exchange during periods of drought compared to diploids [22]. However, the 87% higher xylem hydraulic conductivity (KH) and 81% higher specific hydraulic conductivity observed in tetraploids compared to diploids have been shown to enhance drought tolerance. The study also showed that Ch. angustifolium tetraploids took 30% longer than diploids to reach the point of wilting due to water potential.
Another phenotypic difference with potential physiological consequences is the higher fresh-to-dry weight ratio observed in polyploids compared to diploids. The high water content of polyploids suggests that they have a greater capacity to regulate osmotic pressure within the cell. Their slower growth rate is also believed to reduce water use, thus avoiding extensive cellular damage [108,110]. Deng et al. [110] compared the antioxidant response and stomatal behaviour of tetraploid and octaploid tobacco plants under conditions of drought stress, low temperature, and nutrient deficiency. They demonstrated that, under soil water deficit conditions, octaploid plants (2n = 8×) exhibited lower H2O2 accumulation and a stronger capacity to scavenge reactive oxygen species than tetraploid plants (2n = 4×). Furthermore, under drought stress conditions, octaploids had a significantly longer survival time of approximately 120% compared to tetraploids. Additionally, studies of polyploids revealed that autotetraploids of the Redchief cultivar were more resilient to water deficit than diploids. Under limited water supply, tetraploids did not respond by reducing their leaf area or main shoot length [112]. A ten-month study of diploid and tetraploid Citrus wilsonii plants provides an interesting example that confirms the superior drought tolerance of polyploids [113]. After 21 days without water, the diploids’ leaves had noticeably wilted and exhibited more cellular damage than the tetraploids. The diploids also exhibited a 1.45-fold greater decrease in soil moisture content, a 1.24-fold greater decrease in relative water content, and a 1.54-fold greater electrolyte leakage than the tetraploids [113]. In addition, they exhibited a significantly greater decrease in net photosynthesis rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and Fv/Fm, chlorophyll a and b content, as well as carotenoids. This indicates that tetraploids exhibit higher photosynthetic activity. Xu et al. [116] compared the activity of enzymes related to drought stress tolerance and the productivity of related metabolites in three ploidy lines of Populus ussuriensis Kom. under short-term drought stress (3, 6, 9, or 12 days). The authors demonstrated that triploids and tetraploids exhibited greater drought tolerance than diploids, as evidenced by reduced leaf damage and favourable physiological and biochemical indicators of drought tolerance. Among the polyploids examined, it was the triploids that exhibited considerably reduced malondialdehyde (MDA) content. The presence of MDA indicates cellular damage due to oxidative stress. Furthermore, the triploids exhibited the highest activity of the antioxidant enzymes POD, SOD, and CAT.
Fariaszewska et al. [114] reported significant differences in photosynthetic parameters and water use efficiency among the following five diploid, tetraploid, and hexaploid varieties of forage grass species: Lolium perenne L., L. multiflorum Lam., Festuca pratensis Huds., F. arundinacea Schreb., and Festulolium braunii (K. Richt.) A. Camus. These species were grown in a greenhouse under mild drought stress (40% of the field water capacity) over four consecutive periods. During growing periods II, III, and IV, the authors found that tetraploid cultivars (Meltador, Melmia, and Marifest Tp) most often had significantly higher Pn, Gs, and Tr values than diploid cultivars (Melluck, Meldiva, and Merifest). Moreover, under drought stress, the greatest increase in proline and phenolic acid contents was observed in tetraploid varieties (Marifest Tp, Meltador, and Melmia).
Martignago et al. [130] state that plants have developed various strategies to adapt to drought stress conditions. One such strategy is the closing the stomata to reduce turgor loss in plant cells. This process mainly depends on abscisic acid (ABA), the presence of which regulates the action of ion channels in the cell membranes of stomatal cells. Del Pozo et al. [111] demonstrated that Arabidopsis thaliana tetraploids increased their tolerance to salinity and drought stress by reducing the rate of ABA-regulated stomatal transpiration. Allario et al. [31] also conducted an interesting study on this topic, evaluating the effect of drought on diploid V/2xRL and autotetraploid V/4xRL Rangpur lime (Citrus × limonia Osbeck) plants grafted with Valencia Delta sweet orange (Citrus sinensis (L.) Osbeck) scions. Evidence of this was seen in the leaves and roots of the plants, which had twice and five times the ABA content, respectively. The V/4xRL plants also exhibited lower stomatal conductance (Gs) values and exhibited less wilting than the V/2xRL plants due to hormonal signalling in root–stem communication.
As illustrated above, polyploidisation can provide a variety of advantages, including enhanced drought resilience, in a range of crop species. However, research conducted by Yu et al. [131] showed that six tetraploid rice varieties (4X) had lower drought tolerance than their diploid counterparts (2X). This was evident in the 4X varieties having lower plant height, fewer shoots, and lighter grain. The authors state that this phenomenon is primarily caused by a significant reduction in photosynthesis rates. They also suggested that chromosome doubling magnifies genomic instability and chromatin accessibility, which can have negative effects under drought stress.

6.2. Salt Stress

Another important abiotic factor is salinity stress. This occurs when the salt concentration in the soil exceeds 10 mol m−3. Approximately 10% of the world’s cultivated land becomes saline each year, especially in semi-arid, irrigated, and industrialised regions. This renders them unfit for agricultural use [132]. Salt stress leads to osmotic stress and the excessive accumulation of Na+ and Cl ions. The initial effects of increasing ion concentrations in plants are very similar to those observed during drought stress. These include chlorosis and necrosis on leaf margins, as well as premature leaf drop. Disruption to the plant’s ion economy leads to increased abscisic acid levels and reduced leaf water potential, stomatal conductance, and photosynthetic efficiency. Consequently, plant growth and development decrease [133].
The effects of salt stress on plants, particularly polyploid plants, are not well understood or documented. As Dubkovsky and Dvorak [134] state, hexaploid T. aestivum exhibits enhanced salt tolerance compared to tetraploid wheat. Yang et al. [118] conducted a 30-day study investigating the impact of induced genome polyploidisation on the physiological response to salinity in hexaploid wheat (Triticum aestivum L.), its diploid (Aegilops tauschii Coss.), and tetraploid (T. turgidum Schrank ex Schübl.) Thell.) ancestor. The authors demonstrated that the hexaploids had a much lower Na+ content and a higher K+/Na+ ratio in their spikes than the tetraploids. Furthermore, the hexaploids had a higher Na+ content in their roots than the tetraploids, indicating a greater capacity for Na+ retention. Unlike tetraploids, hexaploids possesses a mechanism for sequestering Na+, which interrupts ion transport to above-ground organs. Hexaploid wheat (T. aestivum) exhibited advantageous photosynthetic traits from its progenitors, resulting in increased photosynthetic capacity. Duplication of the rice genome has been shown to improve tolerance to salinity stress by reducing the absorption of harmful sodium (Na+) ions and increasing the efficiency of hydrogen (H+) proton efflux at the tips of the roots of the tetraploid cultivar Nipponbare-4× compared to the diploid Nipponbare-2× [119]. Analysis of the ion homeostasis of Plumbago auriculata Lam. autotetraploids subjected to salt stress revealed that, although they accumulated more Na+ in their stems and leaves and more Cl- in their roots than diploids did, they sequestrated these toxic ions more efficiently in their cellular vacuoles and removed them from their leaves at a significantly higher rate. Consequently, the tetraploids demonstrated enhanced salt tolerance [120]. Ruiz et al. [117] also observed differences in salinity tolerance between diploid and tetraploid citrus seedlings cultured in a medium supplemented with 40 mM NaCl. On average, tetraploid seedlings were found to be more tolerant of salt stress than diploids. The rate of chloride uptake and translocation from roots to shoots was 1.4-fold higher in diploids than in tetraploids, while the CO2 assimilation rate in salt-treated diploid genotypes was 1.5-fold lower. This was due to the toxic effect of Cl ions and the loss of photosynthetic capacity in diploids. An additional effect was caused by the increased amount of genetic material in polyploids, resulting in differences in the morphological and histological characteristics of the roots. These differences impacted the hydraulic conductivity of the root system and transpiration rate, ultimately contributing to the increased salinity tolerance of tetraploids [117].
The relationship between genome ploidy and chloroplast function and photosynthetic efficiency has been revealed. Severe salt stress (500 mM NaCl) was found to significantly reduce the levels of total chlorophyll (Chl), chlorophyll a and b, as well as stomatal and intercellular conductance, in Robinia pseudoacacia L. tetraploids, compared to diploids [123]. This suggests that polyploids can acclimatise more easily to osmotic stress. Further supporting the enhanced adaptation of tetraploids to salt stress despite a reduction in the abundance of proteins involved in photosystem electron transport (ATP synthases alpha, beta, and delta), no significant decrease in net photosynthesis was observed compared to diploid plants. This suggests that tetraploids may employ distinct defence mechanisms in response to salt stress compared to diploids. Yan et al. [122] compared the responses of diploids and tetraploids of honeysuckle (Lonicera japonica Thunb.) to salt stress and found differences in chlorophyll fluorescence parameters and the functioning of photosystem II and I (PSII and PSI). Tetraploids exhibited a significantly smaller decrease in both photosynthetic rate and decarboxylation efficiency. They also showed no evidence of photoinhibition of PSII and PSI, nor a decrease in the maximum quantum yield for PSII. This was due, in part, to increased Na+ exclusion from the roots and reduced ion transport from the roots to the leaves. According to Yan et al. [121], sodium (Na+) is a major toxic component for plants. Accumulation of sodium in leaves negatively affects the activity of RuBisCO, leading to the inhibition of CO2 fixation and increased generation of reactive oxygen species (ROS). This in turn inactivates photosystems II (PSII) and I (PSI).
In the presence of salt stress, detoxification enzymes play a significant role. These include enzymes that remove superoxide (SOD and CAT), enzymes that degrade hydrogen peroxide (POD), and enzymes involved in the metabolism of phenolic compounds. Additionally, there are enzymes that promote the formation of stress-protective metabolites [135]. As reported by Meng et al. [123], high salinity stress (500 mM) caused H2O2 accumulation and changes in the activity of the antioxidant enzyme in R. pseudoacacia polyploids. When grown under greenhouse conditions, the tetraploids exhibited higher superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities than the diploids. They also exhibited higher levels of glutathione S-transferase (GST) and glutathione reductase (GR) activity, as well as significantly higher levels of dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) activity. This suggests that the Halliwell–Asada pathway effectively alleviates salt stress in R. pseudoacacia polyploids. Malondialdehyde is an important indicator of the severity of oxidative stress. An increase in its concentration indicates oxidative damage to lipids. Conversely, a decrease in its tissue content indicates a reduction in stress. Tu et al. [119] demonstrated a reduction in malondialdehyde (MDA) concentration in tetraploid rice varieties subjected to salinity stress. This suggests that rice tetraploids can prevent lipid peroxidation and preserve cell membrane integrity, in the presence of salt stress. Tetraploids also exhibited reduced root growth inhibition and significantly increased proline accumulation. Furthermore, Bonnin et al. [124] conducted a study involving the physiological and biochemical analysis of salt stress tolerance in various citrus species at a concentration of 90 mM NaCl. They found that tetraploid trifoliate oranges (Poncirus trifoliata (L.) Raf.) and Cleopatra mandarins (Citrus reshni Hort. ex Tan.) had lower levels of MDA in their leaves and roots than their diploid counterparts. In addition, significantly higher proline accumulation was observed in the roots of tetraploid Cleopatra mandarins, suggesting a greater capacity to withstand salt-induced osmotic stress. However, it is worth noting that Mouhaya et al. [136] obtained different results regarding salt stress tolerance in allotetraploid individuals by fusing the protoplasts of diploid P. trifoliata and Citrus deliciosa Ten. The polyploids exhibited a significantly higher level of susceptibility to drought stress than their diploid parental forms. Under salinity conditions ranging from 50 to 400 mM NaCl, the tetraploids accumulated higher concentrations of toxic Cl ions and exhibited a decrease in maximum light output of PSII.

6.3. Temperature Stresses

6.3.1. Heat Stress

Rising global temperatures caused by climate change have made heat stress a key factor in limiting plant productivity. Photosynthetic activity in chloroplasts is considered to be the cellular function that is most sensitive to heat. Increasing temperatures alter the reduction–oxidation properties of PSII acceptors, reducing the efficiency of photosynthetic electron transport in both photosystems. In order to select Angelonia angustifolia Benth. plants that are heat-tolerant and produce more flowers with extended flowering period, Tsai et al. [137] exposed diploid (2n = 2×), triploid (2n = 3×), and tetraploid (2n = 4×) plants to two temperature ranges: 25/20 °C and 30/25 °C. Under elevated temperature conditions (30/25 °C), a significant reduction was observed in plant height, stem diameter, leaf SPAD-502 values, net photosynthetic rate, and stomatal conductance. The greatest decrease in these morphological parameters was observed in diploids. Additionally, it was observed that triploids and tetraploids had thicker leaves than diploids, enabling them to store significant amounts of water necessary for maintaining leaf thermal stability. Among the polyploids best adapted to high temperatures (30/25 °C), triploids exhibited the greatest number of branches and flowers. This suggests that A. angustifolia polyploids are more tolerant of high temperatures than diploids, probably due to their ability to maintain a higher rate of photosynthesis and regulate stomatal transpiration more efficiently. This, in turn, enables them to regulate leaf temperature more effectively. A similar mechanism conditioning increased tolerance to heat stress has been observed in hot peppers [138]. Li et al. [139] compared the anatomical and physiological characteristics of diploids and tetraploids of Lonicera japonica that were subjected to a high temperature of 42 °C for 0–6 h. They demonstrated that moderate heat stress did not result in significant damage to PSII in either diploids or tetraploids. However, six hours of heat stress (42 °C) followed by a ten-hour recovery period, resulted in a significant increase in the maximum yield of the PSII system, as determined by the following parameters: Fv/Fm, the electron transport rate (ETR), and the effective quantum yield of PSII in tetraploids. Other reports indicate that heat stress also alters the biochemical composition of plants, including their sugar and proline content. These play a significant role in osmotic regulation and counteracting the production of ROS. L. japonica diploids exposed to a high temperature of 42 °C for six hours exhibited greater accumulation of soluble sugars, proline, and MDA in diploids and tetraploids, suggesting increased cellular damage and sensitivity to heat stress. After plants’ recovery, the content of proline decreased only in tetraploids. The content of antioxidant enzymes and antioxidants also plays a key role in increasing plant tolerance to heat stress. Zhang et al. [140] found that in vitro colchicine-treated tetraploids of Dioscorea zingiberensis C. H. Wright exhibited increased heat tolerance (42 °C for 5 days) compared to diploids, which supports this thesis. This is partly due to their higher antioxidant content (ascorbic acid and glutathione) and higher antioxidant enzyme activity (SOD, POD, CAT, APX, and GR). At the same time, the polyploidisation of the D. zingiberensis genome activates the expression of genes that improve adaptation to high temperatures, thereby promoting the spread of the species. Kim et al. [141] suggest that the increased tolerance of Cnidium officinale Makino tetraploids may be due to increased phenolic compounds with strong antioxidant activity.

6.3.2. Cold Stress

Low temperature is an important factor in determining the geographic distribution of species at certain latitudes and in limiting crop yield [142]. This atmospheric factor strongly inhibits reactions in both the light-dependent and light-independent phases of photosynthesis. It leads to a reduction in photosynthesis due to partial stomatal closure, inhibition of electron transport and carbohydrate metabolism, and impaired phloem loading. Studies indicate that naturally occurring polyploids often exhibit superior low-temperature tolerance compared to diploids [143]. Research into this phenomenon and the spread of polyploids in high-altitude regions has revealed that their numbers increase in cold environments. Indeed, low temperatures are one of the most important factors that induce polyploidy in somatic cells. They also stimulate the formation of unreduced gametes (2n), which give rise to polyploids. Consequently, up to 85% of the flora in high-altitude regions of Eurasia and the Arctic are polyploids [144]. Many polyploids exhibit delayed generative development, some even exhibit apomixis or rely on vegetative reproduction. Klatt et al. [145] compared the rate of flower formation, reproductive mode, and seed set in diploid and tetraploid cytotypes of Ranunculus kuepferi Greuter & Burdet. They demonstrated that tetraploids began to flower 30 days later than diploids under moderately cold conditions (+7/−1 °C, light/dark) and produced fewer, less well-developed seeds. Literature data presented by Jiang et al. [146] showed that short-term cold stress (24 h at 0 °C and −5 °C) induced anatomical changes in Plumbago auriculata tetraploids. These changes were characterised by thickened spongy mesophyll, wider leaf stomata and increased chloroplast content. Ultimately, this resulted in increased photosynthesis compared to diploids. Tetraploids also exhibited significantly higher Fv/Fm and Fv/Fo values, as well as significantly lower MDA content, in response to cold stress. This indicates superior PSII activity and greater stability of the membrane system. A study by Oustric et al. [147] showed that grafting onto a polyploid rootstock can increase tolerance to cold stress. This was demonstrated using the common clementine (Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.). During the coldest months of the year, plants grafted onto the tetraploid C/4xCC Carrizo citrange rootstock exhibited a significantly smaller decrease in photosynthesis (Pn), stomatal conductance (Gs), and chlorophyll fluorescence (Fv/Fm) than those grafted onto the diploid C/2xCC rootstock. Their increased tolerance to low-temperature stress was also demonstrated by lower levels of malondialdehyde (MDA) and electrolyte leakage, as well as increased antioxidant enzyme activity. Another important study compared the antioxidant response of tetraploids and octaploids of the Nicotiana benthamiana Domin species under cold stress at 10 °C and 4 °C [110]. The cold caused significantly higher levels of ROS-related parameters and non-enzymatic antioxidant content in octaploids. This provided the plants with a stable redox state, increasing survival time by around 70% compared to tetraploids. Cold stress often negatively affects the photosynthetic apparatus, disrupting sugar synthesis and reducing phosphorylation efficiency. Guo et al. [148] compared the response of diploid and autotetraploid potato lines induced by in vitro culture to 14 days of cold stress at 4 °C. They demonstrated that autotetraploids had lower initial levels of reducing sugars (such as glucose and fructose), as well as a weaker ability to accumulate these sugars after cold treatment. Denaeghel et al. [149] addressed the issue of cold tolerance in Escalonia species, demonstrating that the polyploidisation of the E. rubra (Ruiz & Pav.) Pers. genome enhanced the plants’ cold tolerance, raising the threshold from −7.7 to −11.8 °C.
While the advantages of polyploid plants over diploid ones are clear, it is worth noting that increasing the ploidy level of a species too much does not necessarily promote tolerance to environmental stresses. Lagibo et al. [150] compared the cold tolerance of various 8×, 10×, 14×, and 16× genotypes of Viola × wittrockiana Gams under field conditions, assessing winter survival and chlorophyll fluorescence parameters (Fv/Fm). They demonstrated that the plants’ response under severely cold conditions (−7.7 °C) was independent of ploidy level. The winter survival rate of the hexadecaploid (16×) plants was lower than that of the control plants (8×) but higher than that of the 12× plants. However, based on the percentage reduction in Fv/Fm values, the 16× plants were ranked in the intermediate- to-sensitive (I-S) group for frost tolerance. This contrasts with the sensitive (S) 12× plants, the tolerant (T) 10× and 14× plants, and the control 8× plants.

7. Response of Polyploids to Biotic Stress

In addition to the abiotic factors described above, crop growth and yield are significantly affected by biotic factors including bacteria, fungi, viruses, animals, and weeds. These factors can have a variety of effects on plants (Table 2). They have the potential to disrupt plant growth, compete for water, light, or nutrients. Agrophages, which are categorised as pathogenic microorganisms, can penetrate plants via natural openings in the tissues or through damage to leaves and roots. This can result in a range of adverse effects. Necrotrophic pathogens can colonise living organisms, killing their cells and taking nutrients from them. In contrast, biotrophic pathogens do not kill the host; rather, they feed on the organic matter taken from it, causing various disease symptoms to appear. Hemibiotrophs initially weaken plants and behave like biotrophs. However, when combined with other adverse conditions, they can lead to the death of the plant.

7.1. The Benefits of Genome Polyploidisation Under Biotic Stress Conditions

To the best of our knowledge, only a limited number of studies have been conducted to date that assess how the degree of ploidy affects plant responses to pathogens. In the 1980s, an increased resistance to Phakopsora pachyrhizi was reported in polyploids of Glycine tabacina Labill. Benth. in comparison to diploids, as documented by Burdon and Marshall [151] (Table 2). Levin reports that Gottschalk observed increased resistance to Cercospora in Beta vulgaris L. tetraploids [152]. Chowdhury et al. [153] demonstrated that Brassica campestris (L.) A. R. Clapham tetraploids were significantly less frequently colonised by aphids than their diploid counterparts. Li et al. [108] state that polyploids generally exhibit greater resistance to biotic stresses, including the effects of microbes or pests, than their diploid ancestors. This may be because modifying ploidy levels can increase allelic diversity (i.e., the number of gene copies), generating more gene products responsible for the resistance response [154]. Furthermore, the genetic polymorphism of polyploids has been shown to induce greater variability in molecules that recognise pathogen proteins. This, in turn, conditions the resistance response to a broader spectrum of pathogens. Additionally, biotic stress factors can affect phytohormones in polyploids, inducing changes in the expression of homologous genes responsible for producing secondary metabolites, including alkaloids and terpenes, which determine resistance to herbivorous insects and pathogenic fungi [142,152]. In 1993, Busey et al. [155] found that the Stenotaphrum ‘FX-10’ polyploid genotypes were significantly less frequently colonised by nematodes and exhibited significantly less root damage than ‘FX-313’ diploid genotypes. Another study demonstrated that the synthetic species Impatiens walleriana Hook. f., exhibited superior resistance to powdery mildew (Plasmopara obducens) compared to diploids. Chen et al. [156] report that polyploidy may play a key role in enhancing the resistance of woody plants and trees to fungal diseases. They found that the autotetraploid apple cultivars Hanfu and Gala exhibited superior resistance to diseases caused by Alternaria alternata and Colletotrichum gloeosporides than their diploid counterparts. Švara et al. [157] conducted a series of five greenhouse experiments between 2016 and 2019. They found that autopolyploids of both susceptible and resistant apple cultivars exhibited notably lower severity of apple scab symptoms following infection with various Venturia inaeqalis (Cooke) G. Winter isolates than diploids. Furthermore, they revealed a significant reduction in fungal DNA and substantially lower sporulation of V. inaegalis, compared to that recorded on the leaves of diploids. These results confirm previous reports that polyploidy increases a plant’s resistance to fungal pathogens. More recently, Podwyszyńska et al. [99] reported the production of single tetraploid apple clones and cultivars that are less susceptible to apple scab and fire blight than diploids. The authors’ data indicates that the enhanced resistance observed in tetraploids is due to various factors. These include elevated expression levels of the Rvi6 gene and other genes (e.g., WRKY29, CDPK and MPK4), which are known to be associated with disease resistance in Malus × domestica Borkh. Similarly, greater resistance to fungal diseases was observed in allopolyploids derived from crossing allotetraploids (Ribes nigrum × R. grossularia) and (R. nigrum × R nivenum) [158]. In contrast, Mehlferber et al. [159] studied the interaction between plants of different ploidy levels, phyllosphere microbiota, and an invasive leaf pathogen. They demonstrated that Arabidopsis thaliana autotetraploids exhibited enhanced resistance to Pseudomonas syringae pv. tomato DC3000 compared to diploids, regardless of colonization with beneficial phyllosphere bacteria.
Table 2. The response of polyploid plants to biotic stresses.
Table 2. The response of polyploid plants to biotic stresses.
SpeciesStressResponsePloidyReferences
Biotic Stresses
Brassica campestris (L.) A.R. ClaphamMyzus persicae (Sulzer)Less frequent colonization by aphids than in diploidsTetraploid
(2n = 4× 2)
[153]
Glycine tabacina (Labill.) Benth.Phakopsora pachyrhiziIncreased resistance to Phakopsora pachyrhizi; lower rate of disease development and number of pustules per unit area of leaf compared to diploidsPolyploid[151]
Beta vulgaris (L.)CercosporaIncreased resistance to Cercospora compared to diploidsPolyploid[152]
Stenotaphrum secundatum Walter KuntzeBelonolaimus longicaudatus6.8 times fewer of sting nematodes per pot, slight root damage; transpiration rate unchanged compared to diploidsPolyploid
(2n = 4× = 30)
[155]
Malus x domestica Borkh.Alternaria alternate, Colletotrichum gloeosporioidesLower incidence of disease in autotetraploid plants inoculated with A. alternata after 48 h than in diploid plants. The same trend in the incidence of disease in plants after C. gloeosporioides inoculationAutotetraploid
(2n = 4×)
[156]
Venturia inaequalisAutopolyploidy reduced the severity of apple scab symptoms in two cultivars upon inoculation with two different V. inaequalis isolates. Tetraploid plants exhibited reduced sporulation symptoms compared to their diploid counterparts upon infection, which is attributed to a reduced presence of V. inaequalisTetraploid
(2n = 4×)
[157]
Elevated expression levels of the Rvi6 gene and other genes (e.g., WRKY29, CDPK and MPK4), which are known to be associated with disease resistanceTetraploid
(2n = 4×)
[99]
Arabidopsis thaliana L. HeynhPseudomonas syringae pv. tomato DC3000Increased resistance to P. syringae pv. tomato DC3000, regardless of phyllosphere, beneficial bacteria inoculation; some constitutively activated defences, regardless of colonization by the beneficial bacteria; lower pathogen abundance, higher baseline activation of certain defence genes compared to diploidsTetraploid
(2n = 4×)
[159]
Arabidospis suecica (Fr.) Norrl.Enhanced resistance to P. syringae pv. tomato DC3000 with improved recovery compared with the autotetraploid progenitors, Arabidopsis thaliana and A. arenosaAllotetraploid[160]
Fragaria × ananasa DuchesneXanthomonas fra-gariaeThe increased expression of the FaRXf1o gene made allo-octoploid strawberries resistant to Xanthomonas fragariaeAllo-octoploid
(2n = 8× 4 = 56)
[161]
Aster amellus L.Coleophora obscenellaHigher seed damage by the herbivore; increase in density of C. obscenella larvae in hexaploid than in diploid populationsHexaploid
(2n = 6× 3)
[162]
Butomus umbellatus L.Plectosphaerella cucumerina, Colletotrichum fioriniae, Alternaria alternataLesions on the leaves of triploid genotypes of B. umbellatus infected with various pathogens were larger than those on the leaves of diploids. The mean lesion size was 80% larger in triploids infected by C. fioriniae, 24% larger in those infected by P. cucumerina, and 7% larger in those infected by A. alternata. Triploid leaves infected by P. cucumerina sustained around 100% more damage than diploid leavesTriploid (2n = 3× 1)[163]
Ribes L.Podosphaera morsuvaeSimilar response of tetraploids and diploids to powdery mildew, septoria leaf spot, and anthracnoseTetraploid
(2n = 4×)
[164]
1 3×—triploid, 2 4×–tetraploid, 3 6×—hexaploid, 4 8×—octaploid.
This finding was confirmed through transcriptional studies of plants with different ploidy levels, which demonstrated that autotetraploids’ defence system did not require prior microbial activation and was instead the result of an upregulation of differentially expressed genes (DEG).
As stated by Abeysinghe et al. [160], Arabidospis suecica (Fr.) Norrl. allotetraploids exhibit enhanced resistance to Pseudomonas syringae pv. tomato DC3000 compared to their parental species. In the context of polyploids’ increased resistance to bacterial pathogens, the observations of Roach et al. [161] are also of interest. They demonstrate increased expression of the FaRXf1o gene and resistance to Xanthomonas fragariae in octaploid strawberries.

7.2. The Negative Effects of Genome Polyploidisation Under Biotic Stress Conditions

There are also reports in the literature indicating that polyploidisation can result in the silencing of some genes, and sometimes even parts of the genome. The mechanism leading to gene silencing may include DNA methylation or the formation of heterochromatin segments in chromosome [165]. In some cases, epigenetic modifications in polyploids are associated with the activation of transposons, which can result in the silencing of immune or physiological functions in plants [165]. Consequently, polyploids may be a more appealing food source for herbivores or a more suitable location for pathogens to develop. A study of Aster amellus L. revealed that hexaploid plant populations were significantly more susceptible to insect damage than diploid populations [162]. Harms et al. 2021 [163] found that triploid genotypes of Butomus umbellatus L. infected with various pathogens under in vitro conditions had larger leaf lesions than diploids; however, under in vivo conditions, the opposite was observed. In contrast, Sasnauskas et al. [164] state that artificially induced tetraploids of blackcurrant do not differ significantly from diploids in their resistance to powdery mildew, septoria leaf spot, and anthracnose.
The results presented here demonstrate that genome-wide multiplication can enhance or impair resistance to stress factors. According to Richards et al. [166], whole-genome multiplication generates additional gene copies, which can increase resistance to adverse environmental factors, pathogens, and pests. Polyploid plants interact with their environment by modifying their gene expression patterns [166]. Biotic and abiotic stresses can affect plant hormones. These, in turn, can have a number of effects, including changes in DNA methylation. It is widely accepted that changes in DNA methylation are the primary defence mechanism, triggering the appropriate responses in an attacked plant [167]. Literature reports indicate a correlation between changes in DNA methylation plants and their response to bacterial infections [163]. Research has also been conducted into the correlation between changes in DNA methylation and resistance to pathogens [168]

8. Epigenetic Mechanisms That Determine Polyploid Stress Tolerance

Plants have evolved flexible, short-lived strategies for responding to stress through epigenetic mechanisms. The ability to modify gene expression in a way that is inversely proportional without requiring genomic changes or population differentiation represents a significant evolutionary advantage and form of environment adaptation [166]. One way in which this is evident is through changes in DNA methylation. An interesting study on this topic was conducted by Schinkel et al. [169] revealing changes in the pattern of DNA methylation in tetraploid Ranunculus kuepferi Greuter & Burdet plants compared to diploids. This resulted in specific gene expression, with many of these genes being involved in the response to cold stress. Similar experiments on rice revealed that salt stress induces epigenetic regulation of stress-related genes in tetraploids, including those involved in jasmonic acid synthesis and associated signalling pathways. Ultimately, it results in enhanced stress tolerance of tetraploids [170]. Other epigenetic mechanisms affect DNA methylation and gene silencing, depending on histone modifications. Hexaploid wheat (Triticum aestivum L.) has been shown to exhibit greater salt tolerance than its tetraploid progenitor. In the presence of salinity stress, expression of the histone acetyltransferase, TaHAG1 is induced. However, overexpressing TAHAG1 did not result in the upregulation of TaHKT1;5 and TaHKT1;4, nor did it alter their expression. Research findings demonstrated a clear correlation between TaHAG1 levels and increased H2O2 production. This H2O2 then acted as a signalling molecule, modulating Na+ homeostasis in wheat polyploids under saline conditions [171].
In recent years, significant advances have been made in the study of epigenetic control of gene expression in relation to the stress response in polyploids. These include changes in DNA methylation patterns, histone modifications, and gene silencing via micro RNA. These epigenetic modifications significantly contribute to changes in gene expression levels under stress conditions, thereby providing increased stress tolerance. Despite a significant amount of research being dedicated to investigating the response of polyploids to abiotic stresses, a comprehensive understanding of the mechanisms underlying the acquisition of increased stress tolerance in polyploids remains elusive. Further research is required for cognitive reasons, as well as to explore the potential applications of this knowledge in genetic engineering.

9. Future Research Directions

There are several promising areas of research into plant polyploids. Breeding work aimed at obtaining and introducing polyploid plants that are resistant to stressful conditions, including drought, high temperatures, and soil salinity, will certainly continue. These efforts will have practical effects in reducing losses caused by changing environmental conditions. Large-scale research will be conducted on the resistance of polyploids to pathogens and pests of economic importance. The breeding and cultivation of polyploid plants with a high content of specialised secondary metabolites such as alkaloids, polyphenols, and essential oils, which exhibit multidirectional biological activity, including anti-inflammatory, antibacterial, and antioxidant properties, will be carried out. This will increase the use of polyploid crops in the cosmetics, pharmaceutical, and medical industries (Figure 3). Thanks to new molecular approaches and biotechnological techniques, our understanding of epigenetic modifications at different levels of ploidy and the mechanisms underlying the acquisition of increased tolerance to biotic and abiotic stresses will continue to develop.

10. Conclusions

This review presents a range of natural and artificial methods for inducing polyploidy and their effectiveness in field crops, along with medicinal plants and spices. It provides a thorough evaluation of the physiological effects of polyploidisation, including net photosynthetic rate, stomatal conductance, and transpiration rate, in economically important species. It reveals how the polyploidisation of plant genomes alters their chemical composition. It identifies specific compounds undergoing modification (alkaloids, essential oils, flavonoids, and enzymes) and describes the activity of genes involved in their biosynthesis. The literature review highlights the complexity of polyploidisation and the extensive changes it causes in the plant genome. Recent literature suggests that, in the face of a changing climate and the emergence of extreme weather events such as droughts and high air temperatures, polyploid plants can increase production efficiency while maintaining the high quality of agricultural products compared to their diploid counterparts. A number of polyploids producing desirable secondary metabolites, particularly compounds with health-promoting properties, will find applications in pharmacy and medicine. Furthermore, using polyploids, which have increased resistance to biotic stresses in crops, will certainly promote sustainable agriculture, produce safe food, and reduce the negative impact of agriculture on the environment.

Author Contributions

Conceptualization, A.T.-G. and M.K.-C.; writing—original draft preparation, A.T.-G. and M.K.-C.; writing—review and editing, A.T.-G. and M.K.-C.; visualization, A.T.-G. and M.K.-C.; supervision, A.T.-G.; funding acquisition, A.T.-G. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded as a part of scientific-research sub-programme 1, task 1.16 implemented in 2024–2027, within the statutory activity of the IUNG-PIB, Puławy, Poland, financed by the Polish Ministry of Science and Higher Education.

Data Availability Statement

Not applicable.

Acknowledgments

The authors would like to thank Mariola Staniak of the IUNG-PIB, Puławy, Poland, for providing the figure showing the plant habit of Lolium multiflorum.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Plant habit and leaves of Humulus lupulus. L. “Sybilla”: (A) diploid (2×), tetraploid (4×), and triploid (3×) plants (under greenhouse experiment) (bar = 10 cm), (B) fully expanded mid-position leaves of diploid (2×), tetraploid (4×), and triploid plants (3×) (bar = 10 cm). Source: original photographs by the authors.
Figure 1. Plant habit and leaves of Humulus lupulus. L. “Sybilla”: (A) diploid (2×), tetraploid (4×), and triploid (3×) plants (under greenhouse experiment) (bar = 10 cm), (B) fully expanded mid-position leaves of diploid (2×), tetraploid (4×), and triploid plants (3×) (bar = 10 cm). Source: original photographs by the authors.
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Figure 2. Plant habit of Lolium multiflorum Lam.: tetraploid plant cultivar “Gisel” (4×) (left part of panel), tetraploid plant cultivar “Lotos” (4×), diploid plant cultivar “Tur” (2×) (right part of panel) (bar = 20 cm). Source: original photographs by prof. Staniak M. IUNG-PIB Puławy, Poland.
Figure 2. Plant habit of Lolium multiflorum Lam.: tetraploid plant cultivar “Gisel” (4×) (left part of panel), tetraploid plant cultivar “Lotos” (4×), diploid plant cultivar “Tur” (2×) (right part of panel) (bar = 20 cm). Source: original photographs by prof. Staniak M. IUNG-PIB Puławy, Poland.
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Figure 3. Scheme showing the physiological (including photosynthetic parameters, effectiveness of photosystem II, leaf gas exchange) and biochemical effects of plant genome polyploidisation. Arrows indicate the increased or decreased levels of biological factors. Pn—net photosynthetic rate; Pmax—maximum net photosynthetic rate; Ci—intercellular CO2 concentrations; Gs—stomatal conductance; Tr—transpiration rate; LSP—light saturation points; LCP—light compensation point; 3×—triploid; 4×—tetraploid; 6×—hexaploid. Source: author’s elaboration.
Figure 3. Scheme showing the physiological (including photosynthetic parameters, effectiveness of photosystem II, leaf gas exchange) and biochemical effects of plant genome polyploidisation. Arrows indicate the increased or decreased levels of biological factors. Pn—net photosynthetic rate; Pmax—maximum net photosynthetic rate; Ci—intercellular CO2 concentrations; Gs—stomatal conductance; Tr—transpiration rate; LSP—light saturation points; LCP—light compensation point; 3×—triploid; 4×—tetraploid; 6×—hexaploid. Source: author’s elaboration.
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Table 1. The effect of polyploidisation on the physiological parameters of plants when exposed to abiotic stresses.
Table 1. The effect of polyploidisation on the physiological parameters of plants when exposed to abiotic stresses.
SpeciesStressResponsePloidy LevelReferences
Abiotic Stresses
Nicotiana benthamiana L.Mild droughtLower H2O2 accumulation and a stronger ability to scavenge ROS; higher activity of SOD, CAT, and APX enzymes; more antioxidant accumulation; low ROS accumulation; slight damage; a higher Pn and a slower decline in Ci compared to allotetraploidOctaploid
(2n = 8× 4)
[110]
Severe droughtLower CO2 consumption and higher photosynthetic rate compared to allotetraploid
Arabidopsis thaliana (L.) Heynh.DroughtHigher survival rates after two weeks of water deprivation; increased tolerance to drought due to a reduced stomatal transpiration rate through controlling the density and closure of stomata compared to diploidsTetraploid
(2n = 4× 2)
[111]
Malus × domestica BorkhSignificantly higher chlorophyll content index (CCI); higher water potential; higher physiological parameters such as Pn and Tr than in diploidTetraploid
(2n = 4×)
[112]
Citrus × wilsonii Tan.A significantly smaller decrease in soil moisture content, RWC of roots, and RWC of leaves occurred after 21 days of drought stress; a significantly greater decrease in leaf water potential and electrolyte leakage; lesser declines for Pn, Gs, Fv/Fm, while a greater decline for Tr; higher photosynthetic activities than in diploidTetraploid
(2n = 4×)
[113]
Citrus × limonia OsbeckAfter 11 days of drought, significantly lower Gs values and twice the ABA content in the leaves, as well as five times the ABA content in the rootsTetraploid
(2n = 4×)
[31]
Lolium perenne L.Significantly higher values of Pn, Gs, and Tr in the variety Meltador compared to diploid variety MelluckTetraploid
(2n = 4×)
[114]
L. multiflorum Lam.Significantly higher values of Pn, Gs, and Tr in the variety Melmia compared to diploid variety MeldivaTetraploid
(2n = 4×)
Festuca pratensis Huds.Significantly higher values of Pn, Gs, and Tr in the variety Merifest Tp compared to diploid variety MerifestTetraploid
(2n = 4×)
Acacia senegal (L.) WilldPlants taller than diploids characterised by wider stomata (54%), lower stomata density (31%), and larger seed length and width (10–12%)Tetraploid
(2n = 4×)
[115]
Populus ussuriensis Kom.Less leaf injury (leaf blade discolouration and small necroses) than in diploids under six days of drought stress; significantly lower relative electrical conductivity (REC) and malondialdehyde (MDA) content in leaves; significantly higher activity of the antioxidant enzymes SOD, POD, and CAT than in diploidsTetraploid
(2n = 4×)
[116]
Slight discolouration of the leaf blades after six days drought stress; significantly lower relative electrical conductivity of leaves (REC) and malondialdehyde (MDA) content than in diploids and tetraploids; significantly higher activity of SOD, POD, and CAT than in diploids and tetraploidsTriploid (2n = 3×1)
Chamerion angustifolium (L.) HolubLower stomata density, larger stomata size and larger leaves than in diploids; 87% higher hydraulic conductivity (KH) and 81% higher specific hydraulic conductivity (KS); 20% larger mean hydraulic vessel diameter and 26% fewer vessels than in diploidTetraploid
(2n = 4× = 72)
[22]
Citrus triptera x Citrus sinensis (Carrizo citrange CC)SaltChloride uptake and translocation from roots to shoots 1.4-fold higher in diploids than in tetraploids, CO2 assimilation rate 1.5-fold lower; root hydraulic conductance and leaf transpiration rate 58% and 17% lower, respectively, in tetraploids than in diploids; net CO2 assimilation rate 1.5-fold higher than in diploids; much lower leaf damageTetraploid
(2n = 4×)
[117]
Triticum aestivum L.Significantly higher survival rate than the diploid and tetraploid plants (species); stronger root Na+ retention capacity from diploids; higher Gs and Pn than both diploids and tetraploids; much higher chlorophyll and starch contents than in tetraploidsHexaploid
(2n = 6× 3)
[118]
Oryza sativa L.Significantly lower the restriction degree of root length; more significant increase in fresh weight of total roots; increased proline content; marked decrease in soluble sugars and malondialdehyde in roots; a significant decrease in Na+ content compared to diploidTetraploid
(2n = 4×)
[119]
Plumbago auriculata Lam.Morphology, photosynthetic efficiency, and chloroplast structure modified less than in diploids; significantly higher proline and soluble sugar content than in diploids, while H2O2 and MDA content lower; an increased accumulation of Na+ in stems and leaves and an increased accumulation of Cl− in roots but less K+ loss in roots compared with diploidTetraploid
(2n = 4×)
[120]
Lonicera japonica Thunb. Much smaller decreases in leaf photosynthetic rate and carboxylation efficiency, no significant changes in Fv/Fm; normal coordination between PSII and PSI; higher leaf photosynthetic activity than in diploidsTetraploid
(2n = 4×)
[121]
Greater stability of the photosynthetic apparatus; greater root Na+ exclusion; lower reduction in leaf relative water content; increased accumulation of chlorogenic acid and phenolics in leaves; elevated leaf phenylalanine ammonia-lyase activity and transcription; better maintenance of homeostasis in the leaves than in diploidsTetraploid
(2n = 4×)
[122]
Robinia pseudoacacia L.Greater H2O2 accumulation and higher levels of important antioxidants (SOD, APX, GST, GR, DHAR, MDHAR) compared with diploids; significantly higher Pn, Gs, CiTetraploid
(2n = 4×)
[123]
Poncirus trifoliata (L.) Raf.Lower level of MDA in leaves and roots; significantly higher proline accumulation in the roots than in diploidsTetraploid
(2n = 4×)
[124]
Citrus reshni Hort. ex Tan
1 3×–triploid, 2 4×–tetraploid, 3 6×–hexaploid, 4 8×–octaploid, Pn—net photosynthetic rate; Pmax—maximum net photosynthetic rate; Ci—intercellular CO2 concentrations; Gs—stomatal conductance; Tr—transpiration rate; Fv/Fm—maximum PSII quantum yield; ROS—reactive oxygen species; SOD—superoxide dismutase; CAT—catalase; POD—peroxidase; CCI—chlorophyll content index; APX—ascorbate peroxidase; ABA—abscisic acid; RWC—relative water content; REC—relative electrical conductivity; MDA—malondialdehyde; KH—hydraulic conductivity; KS—specific hydraulic conductivity; PSI/II—photosystem I/II; GST—glutathione S-transferase; GR—glutathione reductase; DHAR—dehydroascorbate reductase; MDHAR—monodehydroascorbate reductase.
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Koziara-Ciupa, M.; Trojak-Goluch, A. The Effect of Polyploidisation on the Physiological Parameters, Biochemical Profile, and Tolerance to Abiotic and Biotic Stresses of Plants. Agronomy 2025, 15, 1918. https://doi.org/10.3390/agronomy15081918

AMA Style

Koziara-Ciupa M, Trojak-Goluch A. The Effect of Polyploidisation on the Physiological Parameters, Biochemical Profile, and Tolerance to Abiotic and Biotic Stresses of Plants. Agronomy. 2025; 15(8):1918. https://doi.org/10.3390/agronomy15081918

Chicago/Turabian Style

Koziara-Ciupa, Marta, and Anna Trojak-Goluch. 2025. "The Effect of Polyploidisation on the Physiological Parameters, Biochemical Profile, and Tolerance to Abiotic and Biotic Stresses of Plants" Agronomy 15, no. 8: 1918. https://doi.org/10.3390/agronomy15081918

APA Style

Koziara-Ciupa, M., & Trojak-Goluch, A. (2025). The Effect of Polyploidisation on the Physiological Parameters, Biochemical Profile, and Tolerance to Abiotic and Biotic Stresses of Plants. Agronomy, 15(8), 1918. https://doi.org/10.3390/agronomy15081918

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