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Recent Advances and Applications of Biostimulants for Plant Growth Promotion...
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Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation

A special issue of Biomolecules (ISSN 2218-273X). This special issue belongs to the section "Synthetic Biology and Bioengineering".

Deadline for manuscript submissions: closed (15 September 2021) | Viewed by 86287

Special Issue Editor

Dr. Mohamed A. El-Esawi

E-Mail Website
Guest Editor
Botany Department, Faculty of Science, Tanta University, Tanta 31527, Egypt
Interests: plant molecular biology and biotechnology; plant biostimulants; plant-microbe interactions; mycorrhizal fungi and plants; biological control of diseases; abiotic and biotic stresses; heavy metals and phytoremediation; antimicrobials; secondary metabolites and antioxidants; natural products; genetics and molecular phylogeny; plant and microbial omics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The use of plant biostimulants as functional biomolecules is receiving significant scientific interest worldwide and represents one of the innovative technologies currently used to improve plant growth, thereby enhancing crop yield and food production to meet the demands of the increasing global population. Biostimulants include beneficial substances such as protein hydrolysates, fulvic acids, humic substances, and seaweed and plant extracts, as well as phytohormones and beneficial microorganisms such as plant-growth-promoting bacteria and arbuscular mycorrhizal fungi. These substances and microorganisms have shown potential in regulating the antioxidant machinery, redox potential, and secondary metabolism in plants, resulting in higher plant growth and yield and enhanced tolerance to environmental biotic and abiotic stresses. However, the physiological and molecular mechanisms underlying plant–biostimulant interactions under different environmental conditions are still unclear. Consequently, further studies are urgently needed to elucidate the functional mechanisms and regulatory roles of biostimulants. This Special Issue, therefore, welcomes original research articles, reviews, communications, perspective,s and opinions dissecting the functional mechanisms of plant biostimulants under optimal growth conditions or adverse environmental conditions (e.g., drought, salinity, cold stress, heat stress, waterlogging, suboptimal pH values, nutrient deficiency, heavy metals, and microbial diseases). Physiological and molecular approaches to further augmenting stress tolerance and crop productivity under stress conditions are also of particular interest. The high quality articles on plant biostimulants published in this Special Issue will help foster discussions and collaborations within this new field, as well as with designing and formulating other biostimulants.

Dr. Mohamed A. El-Esawi
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Biomolecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • plant biostimulants
  • functional biomolecules
  • phytohormones
  • humic substances
  • beneficial microorganisms
  • plant growth promotion
  • environmental stress tolerance
  • drought
  • salinity
  • cold stress
  • heat stress
  • waterlogging, suboptimal pH values
  • nutrient deficiency
  • heavy metals
  • microbial diseases
  • functional mechanisms
  • genetic engineering
  • gene expression

Published Papers (18 papers)

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14 pages, 2369 KiB  
Article
Effects of Sulfur Assimilation in Pseudomonas fluorescens SS101 on Growth, Defense, and Metabolome of Different Brassicaceae
by Je-Seung Jeon, Desalegn W. Etalo, Natalia Carreno-Quintero, Ric C. H. de Vos and Jos M. Raaijmakers
Biomolecules 2021, 11(11), 1704; https://doi.org/10.3390/biom11111704 - 16 Nov 2021
Cited by 5 | Viewed by 2289
Abstract
Genome-wide analysis of plant-growth-promoting Pseudomonas fluorescens strain SS101 (PfSS101) followed by site-directed mutagenesis previously suggested that sulfur assimilation may play an important role in growth promotion and induced systemic resistance in Arabidopsis. Here, we investigated the effects of sulfur metabolism [...] Read more.
Genome-wide analysis of plant-growth-promoting Pseudomonas fluorescens strain SS101 (PfSS101) followed by site-directed mutagenesis previously suggested that sulfur assimilation may play an important role in growth promotion and induced systemic resistance in Arabidopsis. Here, we investigated the effects of sulfur metabolism in PfSS101 on growth, defense, and shoot metabolomes of Arabidopsis and the Brassica crop, Broccoli. Root tips of seedlings of Arabidopsis and two Broccoli cultivars were treated with PfSS101 or with a mutant disrupted in the adenylsulfate reductase cysH, a key gene in cysteine and methionine biosynthesis. Phenotyping of plants treated with wild-type PfSS101 or its cysH mutant revealed that sulfur assimilation in PfSS101 was associated with enhanced growth of Arabidopsis but with a reduction in shoot biomass of two Broccoli cultivars. Untargeted metabolomics revealed that cysH-mediated sulfur assimilation in PfSS101 had significant effects on shoot chemistry of Arabidopsis, in particular on chain elongation of aliphatic glucosinolates (GLSs) and on indole metabolites, including camalexin and the growth hormone indole-3-acetic acid. In Broccoli, PfSS101 sulfur assimilation significantly upregulated the relative abundance of several shoot metabolites, in particular, indolic GLSs and phenylpropanoids. These metabolome changes in Broccoli plants coincided with PfSS101-mediated suppression of leaf infections by Xanthomonas campestris. Our study showed the metabolic interconnectedness of plants and their root-associated microbiota. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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22 pages, 1764 KiB  
Article
Plant Uptake of Lactate-Bound Metals: A Sustainable Alternative to Metal Chlorides
by Lee J. Opdahl, Ricky W. Lewis, Lee A. Kalcsits, Tarah S. Sullivan and Karen A. Sanguinet
Biomolecules 2021, 11(8), 1085; https://doi.org/10.3390/biom11081085 - 23 Jul 2021
Cited by 1 | Viewed by 2267
Abstract
Global agricultural intensification has prompted investigations into biostimulants to enhance plant nutrition and soil ecosystem processes. Metal lactates are an understudied class of organic micronutrient supplement that provide both a labile carbon source and mineral nutrition for plant and microbial growth. To gain [...] Read more.
Global agricultural intensification has prompted investigations into biostimulants to enhance plant nutrition and soil ecosystem processes. Metal lactates are an understudied class of organic micronutrient supplement that provide both a labile carbon source and mineral nutrition for plant and microbial growth. To gain a fundamental understanding of plant responses to metal lactates, we employed a series of sterile culture-vessel experiments to compare the uptake and toxicity of five metals (Zn, Mn, Cu, Ni, and Co) supplied in lactate and chloride salt form. Additionally, primary root growth in plate-grown Arabidopsis thaliana seedlings was used to determine optimal concentrations of each metal lactate. Our results suggest that uptake and utilization of metals in wheat (Triticum aestivum L.) when supplied in lactate form is comparable to that of metal chlorides. Metal lactates also have promotional growth effects on A. thaliana seedlings with optimal concentrations identified for Zn (0.5–1.0 µM), Mn (0.5–1.0 µM), Cu (0.5 µM), Ni (1.0 µM), and Co (0.5 µM) lactate. These findings present foundational evidence to support the use of metal lactates as potential crop biostimulants due to their ability to both supply nutrients and stimulate plant growth. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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13 pages, 2234 KiB  
Article
JMJ Histone Demethylases Balance H3K27me3 and H3K4me3 Levels at the HSP21 Locus during Heat Acclimation in Arabidopsis
by Nobutoshi Yamaguchi and Toshiro Ito
Biomolecules 2021, 11(6), 852; https://doi.org/10.3390/biom11060852 - 07 Jun 2021
Cited by 12 | Viewed by 3684
Abstract
Exposure to moderately high temperature enables plants to acquire thermotolerance to high temperatures that might otherwise be lethal. In Arabidopsis thaliana, histone H3 lysine 27 trimethylation (H3K27me3) at the heat shock protein 17.6C (HSP17.6C) and HSP22 loci is removed by [...] Read more.
Exposure to moderately high temperature enables plants to acquire thermotolerance to high temperatures that might otherwise be lethal. In Arabidopsis thaliana, histone H3 lysine 27 trimethylation (H3K27me3) at the heat shock protein 17.6C (HSP17.6C) and HSP22 loci is removed by Jumonji C domain-containing protein (JMJ) histone demethylases, thus allowing the plant to ‘remember’ the heat experience. Other heat memory genes, such as HSP21, are downregulated in acclimatized jmj quadruple mutants compared to the wild type, but how those genes are regulated remains uncharacterized. Here, we show that histone H3 lysine 4 trimethylation (H3K4me3) at HSP21 was maintained at high levels for at least three days in response to heat. This heat-dependent H3K4me3 accumulation was compromised in the acclimatized jmj quadruple mutant as compared to the acclimatized wild type. JMJ30 directly bound to the HSP21 locus in response to heat and coordinated H3K27me3 and H3K4me3 levels under standard and fluctuating conditions. Our results suggest that JMJs mediate the balance between H3K27me3 and H3K4me3 at the HSP21 locus through proper maintenance of H3K27me3 removal during heat acclimation. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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20 pages, 4443 KiB  
Article
Transcriptional Cascade in the Regulation of Flowering in the Bamboo Orchid Arundina graminifolia
by Sagheer Ahmad, Chuqiao Lu, Jieqiu Wu, Yonglu Wei, Jie Gao, Jianpeng Jin, Chuanyuan Zheng, Genfa Zhu and Fengxi Yang
Biomolecules 2021, 11(6), 771; https://doi.org/10.3390/biom11060771 - 21 May 2021
Cited by 12 | Viewed by 2467
Abstract
Flowering in orchids is the most important horticultural trait regulated by multiple mechanisms. Arundina graminifolia flowers throughout the year unlike other orchids with a narrow flowering span. However, little is known of the genetic regulation of this peculiar flowering pattern. This study identifies [...] Read more.
Flowering in orchids is the most important horticultural trait regulated by multiple mechanisms. Arundina graminifolia flowers throughout the year unlike other orchids with a narrow flowering span. However, little is known of the genetic regulation of this peculiar flowering pattern. This study identifies a number of transcription factor (TF) families in five stages of flower development and four tissue types through RNA-seq transcriptome. About 700 DEGs were annotated to the transcription factor category and classified into 35 TF families, which were involved in multiple signaling pathways. The most abundant TF family was bHLH, followed by MYB and WRKY. Some important members of the bHLH, WRKY, MYB, TCP, and MADS-box families were found to regulate the flowering genes at transcriptional levels. Particularly, the TFs WRKY34 and ERF12 possibly respond to vernalization and photoperiod signaling, MYB108, RR9, VP1, and bHLH49 regulate hormonal balance, and CCA1 may control the circadian pathway. MADS-box TFs including MADS6, 14, 16, AGL5, and SEP may be important regulators of flowering in A. graminifolia. Therefore, this study provides a theoretical basis for understanding the molecular mechanism of flowering in A. graminifolia. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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15 pages, 10602 KiB  
Article
Modulation of the Antioxidant Defense System by Exogenous l-Glutamic Acid Application Enhances Salt Tolerance in Lentil (Lens culinaris Medik.)
by Jannatul Fardus, Md. Shahadat Hossain and Masayuki Fujita
Biomolecules 2021, 11(4), 587; https://doi.org/10.3390/biom11040587 - 16 Apr 2021
Cited by 25 | Viewed by 2841
Abstract
Salt stress greatly disturbs the growth, morpho-physiological, and biochemical performance of plants. However, different physiological processes and acclimation mechanisms can be induced under stress, while some of them can be modulated by the appropriate chemical stimulus. The objective of this study was to [...] Read more.
Salt stress greatly disturbs the growth, morpho-physiological, and biochemical performance of plants. However, different physiological processes and acclimation mechanisms can be induced under stress, while some of them can be modulated by the appropriate chemical stimulus. The objective of this study was to evaluate the impact of exogenous pretreatment with 10 mM l-glutamic acid (l-Glu) on the physiological and biochemical parameters of lentil (Lensculinaris Medik.) under 110 mM NaCl stress. Salt stress inhibited the growth and reduced the photosynthetic pigment (chlorophylls and carotenoids) level, water content, and survival of lentil seedlings during recovery from the stress. Salt stress also induced oxidative damage, as indicated by higher hydrogen peroxide and malonaldehyde contents and electrolyte leakage, by interrupting the antioxidant defense system and promoting the accumulation of toxic levels of Na+. However, l-Glu pretreatment mitigated the salt-induced damage in lentil seedlings by reducing the accumulation of Na+, maintaining ion homeostasis, and increasing the activities of antioxidant enzymes (catalase and ascorbate peroxidase). As a result, salt-induced oxidative damage was reduced, seedling growth and photosynthetic pigment contents were enhanced, and the survival rate of the lentil seedlings was improved in response to salt stress, indicating an ameliorative role for l-Glu in lentil seedling growth under salt stress. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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24 pages, 4858 KiB  
Article
Silymarin-Enriched Biostimulant Foliar Application Minimizes the Toxicity of Cadmium in Maize by Suppressing Oxidative Stress and Elevating Antioxidant Gene Expression
by Hesham F. Alharby, Hassan S. Al-Zahrani, Khalid R. Hakeem, Hameed Alsamadany, El-Sayed M. Desoky and Mostafa M. Rady
Biomolecules 2021, 11(3), 465; https://doi.org/10.3390/biom11030465 - 21 Mar 2021
Cited by 41 | Viewed by 3474
Abstract
For maize, the potential preventive role of foliar spraying with an extract derived from maize grain (MEg, 2%), silymarin (Sm, 0.5 mM), or silymarin-enriched MEg (MEg-Sm) in attenuating the stress effects of cadmium (Cd, 0.5 mM) was examined using a completely randomized design [...] Read more.
For maize, the potential preventive role of foliar spraying with an extract derived from maize grain (MEg, 2%), silymarin (Sm, 0.5 mM), or silymarin-enriched MEg (MEg-Sm) in attenuating the stress effects of cadmium (Cd, 0.5 mM) was examined using a completely randomized design layout. Under normal conditions, foliar spraying with MEg, Sm, or MEg-Sm was beneficial (with MEg-Sm preferred) for maize plants, whereas the benefit was more pronounced under Cd stress. The use of Cd through irrigation water decreased plant growth traits, photosynthetic efficiency, including instantaneous carboxylation efficiency, Fv/Fm, and pigment contents, and hormonal contents (e.g., auxin, gibberellins, cytokinins including trans-zeatin, and salicylic acid). These undesired findings were due to an increase in Cd content, leading to increased levels of oxidative stress (O2•− and H2O2), ionic leakage, and lipid peroxidation. Therefore, this damage resulted in an increase in the activities of nonenzymatic antioxidants, Sm, antioxidative enzymes, and enzyme gene expression. However, under Cd stress, although foliar spray with MEg or Sm had better findings than control, MEg-Sm had better findings than MEg or Sm. Application of MEg-Sm greatly increased photosynthesis efficiency, restored hormonal homeostasis, and further increased the activities of various antioxidants, Sm, antioxidative enzymes, and enzyme gene expression. These desired findings were due to the suppression of the Cd content, and thus the levels of O2•−, H2O2, ionic leakage, and lipid peroxidation, which were positively reflected in the growth and accumulation of dry matter in maize plants. The data obtained in this study recommend applying silymarin-enriched maize grain extract (MEg-Sm at 0.24 g Sm L−1 of MEg) as a spray solution to maize plants when exposed to excess Cd in soil or irrigation water. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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13 pages, 1103 KiB  
Article
Fractionation of Heavy Metals in Multi-Contaminated Soil Treated with Biochar Using the Sequential Extraction Procedure
by Mahrous Awad, Zhongzhen Liu, Milan Skalicky, Eldessoky S. Dessoky, Marian Brestic, Sonia Mbarki, Anshu Rastogi and Ayman EL Sabagh
Biomolecules 2021, 11(3), 448; https://doi.org/10.3390/biom11030448 - 17 Mar 2021
Cited by 40 | Viewed by 3438
Abstract
Heavy metals (HMs) toxicity represents a global problem depending on the soil environment’s geochemical forms. Biochar addition safely reduces HMs mobile forms, thus, reducing their toxicity to plants. While several studies have shown that biochar could significantly stabilize HMs in contaminated soils, the [...] Read more.
Heavy metals (HMs) toxicity represents a global problem depending on the soil environment’s geochemical forms. Biochar addition safely reduces HMs mobile forms, thus, reducing their toxicity to plants. While several studies have shown that biochar could significantly stabilize HMs in contaminated soils, the study of the relationship of soil properties to potential mechanisms still needs further clarification; hence the importance of assessing a naturally contaminated soil amended, in this case with Paulownia biochar (PB) and Bamboo biochar (BB) to fractionate Pb, Cd, Zn, and Cu using short sequential fractionation plans. The relationship of soil pH and organic matter and its effect on the redistribution of these metals were estimated. The results indicated that the acid-soluble metals decreased while the fraction bound to organic matter increased compared to untreated pots. The increase in the organic matter metal-bound was mostly at the expense of the decrease in the acid extractable and Fe/Mn bound ones. The highest application of PB increased the organically bound fraction of Pb, Cd, Zn, and Cu (62, 61, 34, and 61%, respectively), while the BB increased them (61, 49, 42, and 22%, respectively) over the control. Meanwhile, Fe/Mn oxides bound represents the large portion associated with zinc and copper. Concerning soil organic matter (SOM) and soil pH, as potential tools to reduce the risk of the target metals, a significant positive correlation was observed with acid-soluble extractable metal, while a negative correlation was obtained with organic matter-bound metal. The principal component analysis (PCA) shows that the total variance represents 89.7% for the TCPL-extractable and HMs forms and their relation to pH and SOM, which confirms the positive effect of the pH and SOM under PB and BB treatments on reducing the risk of the studied metals. The mobility and bioavailability of these metals and their geochemical forms widely varied according to pH, soil organic matter, biochar types, and application rates. As an environmentally friendly and economical material, biochar emphasizes its importance as a tool that makes the soil more suitable for safe cultivation in the short term and its long-term sustainability. This study proves that it reduces the mobility of HMs, their environmental risks and contributes to food safety. It also confirms that performing more controlled experiments, such as a pot, is a disciplined and effective way to assess the suitability of different types of biochar as soil modifications to restore HMs contaminated soil via controlling the mobilization of these minerals. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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18 pages, 3823 KiB  
Article
Exogenous 3,3′-Diindolylmethane Improves Vanadium Stress Tolerance in Brassica napus Seedling Shoots by Modulating Antioxidant Enzyme Activities
by Arun Gokul, Mogamat Fahiem Carelse, Lee-Ann Niekerk, Ashwil Klein, Ndiko Ludidi, David Mendoza-Cozatl and Marshall Keyster
Biomolecules 2021, 11(3), 436; https://doi.org/10.3390/biom11030436 - 16 Mar 2021
Cited by 4 | Viewed by 2225
Abstract
3,3′-diindolylmethane (DIM) belongs to a family of indole glucosinolate compounds that have been shown to improve Brassica napus growth through the modulation of reactive oxygen species when applied exogenously. The B. napus cultivar AV Garnet was previously identified as a vanadium-sensitive cultivar. Therefore, [...] Read more.
3,3′-diindolylmethane (DIM) belongs to a family of indole glucosinolate compounds that have been shown to improve Brassica napus growth through the modulation of reactive oxygen species when applied exogenously. The B. napus cultivar AV Garnet was previously identified as a vanadium-sensitive cultivar. Therefore, in this study we investigated whether exogenous DIM could improve the vanadium tolerance of AV Garnet. We performed the following experiments: seed germination assessment, dry weight assessment, cell viability assay, chlorophyll content assay, malondialdehyde (MDA) assay, conjugated diene (CD) content assay, hydrogen peroxide (H2O2) content assay, superoxide (O2−) content determination, methylglyoxal (MG) content determination, hydroxyl radical (·OH) concentration determination, ascorbate peroxidase (APX) activity assay, superoxide dismutase (SOD) activity assay, glyoxalase I (Gly I) activity assay, glutathione S-transferase (GST) activity assay and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis for vanadium content determination. Under vanadium stress, exogenous DIM increased the seed germination percentage, shoot dry weight, cell viability and chlorophyll content. Exogenous DIM also led to a decrease in MDA, CD, H2O2, O2−, MG and ·OH, under vanadium stress in the shoots. Furthermore, DIM application led to an increase in the enzymatic activities of APX, SOD, Gly I and GST under vanadium stress. Interestingly, under vanadium stress, DIM treatment did not alter vanadium content in B. napus shoots. Our results indicate that exogenous application of DIM can improve B. napus seedling shoot growth and biomass under vanadium stress by priming the antioxidant enzymes via reactive oxygen species (ROS) signaling. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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19 pages, 1742 KiB  
Article
The Application of a Plant Biostimulant Based on Seaweed and Yeast Extract Improved Tomato Fruit Development and Quality
by Giuseppe Mannino, Cristina Campobenedetto, Ivano Vigliante, Valeria Contartese, Carla Gentile and Cinzia M. Bertea
Biomolecules 2020, 10(12), 1662; https://doi.org/10.3390/biom10121662 - 12 Dec 2020
Cited by 50 | Viewed by 5730
Abstract
Plant biostimulants are under investigation as innovative products to improve plant production and fruit quality, without resulting in environmental and food contaminations. Here, the effects of the application of Expando, a biostimulant based on seaweed and yeast extracts, on plant productivity, fruit ripening [...] Read more.
Plant biostimulants are under investigation as innovative products to improve plant production and fruit quality, without resulting in environmental and food contaminations. Here, the effects of the application of Expando, a biostimulant based on seaweed and yeast extracts, on plant productivity, fruit ripening times, and fruit quality of Solanum lycopersicum var. Micro-Tom were evaluated. After biostimulant treatment, a two-week reduction of ripening times and a concomitant enhancement of the production percentage during the earliest ripening times, in terms of both fruit yield (+110%) and size (+85%), were observed. Concerning fruit quality, proximate analysis showed that tomatoes treated with the biostimulant had better nutritional composition compared to untreated samples, since both the quality of unsatured fatty acids (C16:3ω3: +328%; C18:2ω6: −23%) and micronutrients essential for human health (Fe: +14%; Cu: +21%; Zn: +24%) were increased. From a nutraceutical point of view, despite strong changes in bioactive compound profile not being observed, an increase of the antioxidant properties was recorded in fruits harvested by plants treated with the biostimulant (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS): +38%; 2,2-diphenyl-1-picrylhydrazyl (DPPH): +11%). In conclusion, the biostimulant application was able to reduce the ripening times and fruit size, while slightly increasing nutritional and nutraceutical values, leading to more marketable tomato fruits. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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17 pages, 2841 KiB  
Article
Molybdenum Supply Alleviates the Cadmium Toxicity in Fragrant Rice by Modulating Oxidative Stress and Antioxidant Gene Expression
by Muhammad Imran, Saddam Hussain, Mohamed A. El-Esawi, Muhammad Shoaib Rana, Muhammad Hamzah Saleem, Muhammad Riaz, Umair Ashraf, Mouloumdema Pouwedeou Potcho, Meiyang Duan, Imran Ali Rajput and Xiangru Tang
Biomolecules 2020, 10(11), 1582; https://doi.org/10.3390/biom10111582 - 21 Nov 2020
Cited by 57 | Viewed by 3829
Abstract
Increasing evidence shows that cadmium (Cd) toxicity causes severe perturbations on growth performance, physio-biochemical and molecular processes in crop plants. Molybdenum (Mo), an essential trace element, plays key roles in oxidative stress tolerance of higher plants. Hence, the present study has been conducted [...] Read more.
Increasing evidence shows that cadmium (Cd) toxicity causes severe perturbations on growth performance, physio-biochemical and molecular processes in crop plants. Molybdenum (Mo), an essential trace element, plays key roles in oxidative stress tolerance of higher plants. Hence, the present study has been conducted to investigate the possible role of Mo in alleviating Cd-induced inhibitions in two fragrant rice cultivars namely Guixiangzhan (GXZ) and Meixiangzhan-2 (MXZ-2). The results revealed that Mo application enhanced the plant dry biomass by 73.24% in GXZ and 58.09% in MXZ-2 under Cd stress conditions, suggesting that Mo supplementation alleviated Cd-induced toxicity effects in fragrant rice. The enhanced Cd-tolerance in fragrant rice plants prompted by Mo application could be ascribed to its ability to regulate Cd uptake and reduce Cd-induced oxidative stress as evident by lower hydrogen peroxide levels, electrolyte leakage and malondialdehyde contents in Cd-stressed plants. The ameliorative role of Mo against Cd-toxicity also reflected through its protection to the photosynthetic pigments, proline and soluble protein. Mo also induced antioxidant defense systems via maintaining higher contents of glutathione and ascorbate as well as enhancing the ROS-detoxifying enzymes such as catalase, peroxidase, superoxide dismutase and ascorbate peroxidase activities and up-regulating transcript abundance in both fragrant rice cultivars under Cd stress. Conclusively, Mo-mediated modulation of Cd toxicity in fragrant rice was through restricting Cd uptake, maintaining photosynthetic performance and alleviating oxidative damages via the strong anti-oxidative defense systems; however, GXZ cultivar is comparatively more Cd tolerant and Mo-efficient as evident from the less growth inhibition and biomass reduction as well as enhanced Mo-induced Cd stress tolerance and less oxidative damage than MXZ-2 fragrant rice cultivar. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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29 pages, 7968 KiB  
Article
Foliar Spray of Fe-Asp Confers Better Drought Tolerance in Sunflower as Compared with FeSO4: Yield Traits, Osmotic Adjustment, and Antioxidative Defense Mechanisms
by Qasim Ali, Shafaqat Ali, Mohamed A. El-Esawi, Muhammad Rizwan, Muhammad Azeem, Abdullah Ijaz Hussain, Rashida Perveen, Mohamed A. El-Sheikh, Mohammed Nasser Alyemeni and Leonard Wijaya
Biomolecules 2020, 10(9), 1217; https://doi.org/10.3390/biom10091217 - 21 Aug 2020
Cited by 14 | Viewed by 3802
Abstract
Different techniques are being employed to reduce the adverse effects of water stress on seed yield and quality of crop plants. The current study aimed to improve the water stress tolerance of field-grown sunflower by foliar-supplied ecofriendly iron-chelated aspartate (Fe-Asp) in comparison with [...] Read more.
Different techniques are being employed to reduce the adverse effects of water stress on seed yield and quality of crop plants. The current study aimed to improve the water stress tolerance of field-grown sunflower by foliar-supplied ecofriendly iron-chelated aspartate (Fe-Asp) in comparison with FeSO4. Water stress decreased the plant growth and yield, accompanied with disturbed water relations, nutrient acquisition, accumulation of amino acids, and antioxidative defense mechanisms. However, lipid peroxidation, total anthocyanin, and photosynthetic pigments were increased. Fertigation of FeSO4 and Fe-Asp as foliar sprays proved effective to reduce the negativities of limited irrigation on biomass production and seed yield, accompanied with a reduction in lipid peroxidation and improvements in water relations, antioxidative defense mechanisms, and leaf photosynthetic pigments. In comparison with FeSO4, foliary applied Fe-Asp better improved the plant water relations with more accumulation of essential amino acids and nutrient acquisition, especially leaf aspartate (Asp) and Fe accumulation which showed better translocation. Overall, foliary applied Fe-Asp proved better for induction of drought tolerance in sunflower plants as compared with FeSO4. The study recommended the use of the ecofriendly Fe-Asp as a foliar spray for better growth and production of sunflower under limited irrigation. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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30 pages, 1192 KiB  
Article
Low Doses of Cuscuta reflexa Extract Act as Natural Biostimulants to Improve the Germination Vigor, Growth, and Grain Yield of Wheat Grown under Water Stress: Photosynthetic Pigments, Antioxidative Defense Mechanisms, and Nutrient Acquisition
by Qasim Ali, Rashida Perveen, Mohamed A. El-Esawi, Shafaqat Ali, Syed Makhdoom Hussain, Maira Amber, Naeem Iqbal, Muhammad Rizwan, Mohammed Nasser Alyemeni, Hamed A. El-Serehy, Fahad A. Al-Misned and Parvaiz Ahmad
Biomolecules 2020, 10(9), 1212; https://doi.org/10.3390/biom10091212 - 20 Aug 2020
Cited by 18 | Viewed by 3922
Abstract
The present study was conducted to investigate the effects of Cuscuta reflexa extract (CRE) on the activities of germination enzymes, seed germination vigor, biomass production, physio-biochemical attributes, and seed yield of water-stressed wheat plants. Different levels of CRE (0, 10, 20, 30, 40, [...] Read more.
The present study was conducted to investigate the effects of Cuscuta reflexa extract (CRE) on the activities of germination enzymes, seed germination vigor, biomass production, physio-biochemical attributes, and seed yield of water-stressed wheat plants. Different levels of CRE (0, 10, 20, 30, 40, and 50%), including water soaking, were used as seed priming. Water stress negatively affected the seed germination, germination enzyme activities, growth, yield, and different physio-biochemical attributes of wheat plants. Low doses of CRE (10, 20, and 30%) ameliorated the adverse effects of water stress on seed germination attributes, and activities of germination enzymes, but negative impacts were recorded at higher doses (40 and 50%) of CRE. Water-stressed wheat plants grown from seeds pre-treated with low doses of CRE also showed better growth and yield as compared with non-treated ones, and that was associated with an improvement in water relations, photosynthetic pigments, nutrient acquisition, reduced lipid peroxidation, and better antioxidative defense mechanisms. The maximum increase in seed yield was 14.77 and 12.32%, found in plants grown from seeds treated with 20% and 10% CRE, respectively. In conclusion, it is suggested that using low doses of CRE as seed priming can contribute to better wheat yield under water stress, especially in semi-arid and arid areas. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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Review

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36 pages, 502 KiB  
Review
Biostimulant Substances for Sustainable Agriculture: Origin, Operating Mechanisms and Effects on Cucurbits, Leafy Greens, and Nightshade Vegetables Species
by Francesco Cristofano, Christophe El-Nakhel and Youssef Rouphael
Biomolecules 2021, 11(8), 1103; https://doi.org/10.3390/biom11081103 - 27 Jul 2021
Cited by 45 | Viewed by 4695
Abstract
Climate change is a pressing matter of anthropogenic nature to which agriculture contributes by abusing production inputs such as inorganic fertilizers and fertigation water, thus degrading land and water sources. Moreover, as the increase in the demand of food in 2050 is estimated [...] Read more.
Climate change is a pressing matter of anthropogenic nature to which agriculture contributes by abusing production inputs such as inorganic fertilizers and fertigation water, thus degrading land and water sources. Moreover, as the increase in the demand of food in 2050 is estimated to be 25 to 70% more than what is currently produced today, a sustainable intensification of agriculture is needed. Biostimulant substances are products that the EU states work by promoting growth, resistance to plant abiotic stress, and increasing produce quality, and may be a valid strategy to enhance sustainable agricultural practice. Presented in this review is a comprehensive look at the scientific literature regarding the widely used and EU-sanctioned biostimulant substances categories of silicon, seaweed extracts, protein hydrolysates, and humic substances. Starting from their origin, the modulation of plants’ hormonal networks, physiology, and stress defense systems, their in vivo effects are discussed on some of the most prominent vegetable species of the popular plant groupings of cucurbits, leafy greens, and nightshades. The review concludes by identifying several research areas relevant to biostimulant substances to exploit and enhance the biostimulant action of these substances and signaling molecules in horticulture. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
27 pages, 832 KiB  
Review
Recent Advances in the Molecular Effects of Biostimulants in Plants: An Overview
by Miguel Baltazar, Sofia Correia, Kieran J. Guinan, Neerakkal Sujeeth, Radek Bragança and Berta Gonçalves
Biomolecules 2021, 11(8), 1096; https://doi.org/10.3390/biom11081096 - 25 Jul 2021
Cited by 60 | Viewed by 11363
Abstract
As the world develops and population increases, so too does the demand for higher agricultural output with lower resources. Plant biostimulants appear to be one of the more prominent sustainable solutions, given their natural origin and their potential to substitute conventional methods in [...] Read more.
As the world develops and population increases, so too does the demand for higher agricultural output with lower resources. Plant biostimulants appear to be one of the more prominent sustainable solutions, given their natural origin and their potential to substitute conventional methods in agriculture. Classified based on their source rather than constitution, biostimulants such as humic substances (HS), protein hydrolysates (PHs), seaweed extracts (SWE) and microorganisms have a proven potential in improving plant growth, increasing crop production and quality, as well as ameliorating stress effects. However, the multi-molecular nature and varying composition of commercially available biostimulants presents challenges when attempting to elucidate their underlying mechanisms. While most research has focused on the broad effects of biostimulants in crops, recent studies at the molecular level have started to unravel the pathways triggered by certain products at the cellular and gene level. Understanding the molecular influences involved could lead to further refinement of these treatments. This review comprises the most recent findings regarding the use of biostimulants in plants, with particular focus on reports of their molecular influence. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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18 pages, 693 KiB  
Review
Sustainable Agriculture Systems in Vegetable Production Using Chitin and Chitosan as Plant Biostimulants
by Mohamad Hesam Shahrajabian, Christina Chaski, Nikolaos Polyzos, Nikolaos Tzortzakis and Spyridon A. Petropoulos
Biomolecules 2021, 11(6), 819; https://doi.org/10.3390/biom11060819 - 31 May 2021
Cited by 89 | Viewed by 8730
Abstract
Chitin and chitosan are natural compounds that are biodegradable and nontoxic and have gained noticeable attention due to their effective contribution to increased yield and agro-environmental sustainability. Several effects have been reported for chitosan application in plants. Particularly, it can be used in [...] Read more.
Chitin and chitosan are natural compounds that are biodegradable and nontoxic and have gained noticeable attention due to their effective contribution to increased yield and agro-environmental sustainability. Several effects have been reported for chitosan application in plants. Particularly, it can be used in plant defense systems against biological and environmental stress conditions and as a plant growth promoter—it can increase stomatal conductance and reduce transpiration or be applied as a coating material in seeds. Moreover, it can be effective in promoting chitinolytic microorganisms and prolonging storage life through post-harvest treatments, or benefit nutrient delivery to plants since it may prevent leaching and improve slow release of nutrients in fertilizers. Finally, it can remediate polluted soils through the removal of cationic and anionic heavy metals and the improvement of soil properties. On the other hand, chitin also has many beneficial effects such as plant growth promotion, improved plant nutrition and ability to modulate and improve plants’ resistance to abiotic and biotic stressors. The present review presents a literature overview regarding the effects of chitin, chitosan and derivatives on horticultural crops, highlighting their important role in modern sustainable crop production; the main limitations as well as the future prospects of applications of this particular biostimulant category are also presented. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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22 pages, 1232 KiB  
Review
Improving Performance of Salt-Grown Crops by Exogenous Application of Plant Growth Regulators
by Md. Quamruzzaman, S. M. Nuruzzaman Manik, Sergey Shabala and Meixue Zhou
Biomolecules 2021, 11(6), 788; https://doi.org/10.3390/biom11060788 - 24 May 2021
Cited by 43 | Viewed by 5531
Abstract
Soil salinity is one of the major abiotic stresses restricting plant growth and development. Application of plant growth regulators (PGRs) is a possible practical means for minimizing salinity-induced yield losses, and can be used in addition to or as an alternative to crop [...] Read more.
Soil salinity is one of the major abiotic stresses restricting plant growth and development. Application of plant growth regulators (PGRs) is a possible practical means for minimizing salinity-induced yield losses, and can be used in addition to or as an alternative to crop breeding for enhancing salinity tolerance. The PGRs auxin, cytokinin, nitric oxide, brassinosteroid, gibberellin, salicylic acid, abscisic acid, jasmonate, and ethylene have been advocated for practical use to improve crop performance and yield under saline conditions. This review summarizes the current knowledge of the effectiveness of various PGRs in ameliorating the detrimental effects of salinity on plant growth and development, and elucidates the physiological and genetic mechanisms underlying this process by linking PGRs with their downstream targets and signal transduction pathways. It is shown that, while each of these PGRs possesses an ability to alter plant ionic and redox homeostasis, the complexity of interactions between various PGRs and their involvement in numerous signaling pathways makes it difficult to establish an unequivocal causal link between PGRs and their downstream effectors mediating plants’ adaptation to salinity. The beneficial effects of PGRs are also strongly dependent on genotype, the timing of application, and the concentration used. The action spectrum of PGRs is also strongly dependent on salinity levels. Taken together, this results in a rather narrow “window” in which the beneficial effects of PGR are observed, hence limiting their practical application (especially under field conditions). It is concluded that, in the light of the above complexity, and also in the context of the cost–benefit analysis, crop breeding for salinity tolerance remains a more reliable avenue for minimizing the impact of salinity on plant growth and yield. Further progress in the field requires more studies on the underlying cell-based mechanisms of interaction between PGRs and membrane transporters mediating plant ion homeostasis. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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23 pages, 1302 KiB  
Review
Biostimulants Application: A Low Input Cropping Management Tool for Sustainable Farming of Vegetables
by Mohamad Hesam Shahrajabian, Christina Chaski, Nikolaos Polyzos and Spyridon A. Petropoulos
Biomolecules 2021, 11(5), 698; https://doi.org/10.3390/biom11050698 - 07 May 2021
Cited by 74 | Viewed by 8500
Abstract
Biostimulants, are a diverse class of compounds including substances or microorganism which have positive impacts on plant growth, yield and chemical composition as well as boosting effects to biotic and abiotic stress tolerance. The major plant biostimulants are hydrolysates of plant or animal [...] Read more.
Biostimulants, are a diverse class of compounds including substances or microorganism which have positive impacts on plant growth, yield and chemical composition as well as boosting effects to biotic and abiotic stress tolerance. The major plant biostimulants are hydrolysates of plant or animal protein and other compounds that contain nitrogen, humic substances, extracts of seaweeds, biopolymers, compounds of microbial origin, phosphite, and silicon, among others. The mechanisms involved in the protective effects of biostimulants are varied depending on the compound and/or crop and mostly related with improved physiological processes and plant morphology aspects such as the enhanced root formation and elongation, increased nutrient uptake, improvement in seed germination rates and better crop establishment, increased cation exchange, decreased leaching, detoxification of heavy metals, mechanisms involved in stomatal conductance and plant transpiration or the stimulation of plant immune systems against stressors. The aim of this review was to provide an overview of the application of plant biostimulants on different crops within the framework of sustainable crop management, aiming to gather critical information regarding their positive effects on plant growth and yield, as well as on the quality of the final product. Moreover, the main limitations of such practice as well as the future prospects of biostimulants research will be presented. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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15 pages, 1685 KiB  
Review
A Review on the Beneficial Role of Silicon against Salinity in Non-Accumulator Crops: Tomato as a Model
by Jonas Hoffmann, Roberto Berni, Jean-Francois Hausman and Gea Guerriero
Biomolecules 2020, 10(9), 1284; https://doi.org/10.3390/biom10091284 - 07 Sep 2020
Cited by 55 | Viewed by 4827
Abstract
Salinity is an abiotic stress that affects agriculture by severely impacting crop growth and, consequently, final yield. Considering that sea levels rise at an alarming rate of >3 mm per year, it is clear that salt stress constitutes a top-ranking threat to agriculture. [...] Read more.
Salinity is an abiotic stress that affects agriculture by severely impacting crop growth and, consequently, final yield. Considering that sea levels rise at an alarming rate of >3 mm per year, it is clear that salt stress constitutes a top-ranking threat to agriculture. Among the economically important crops that are sensitive to high salinity is tomato (Solanum lycopersicum L.), a cultivar that is more affected by salt stress than its wild counterparts. A strong body of evidence in the literature has proven the beneficial role of the quasi-essential metalloid silicon (Si), which increases the vigor and protects plants against (a)biotic stresses. This protection is realized by precipitating in the cell walls as opaline silica that constitutes a mechanical barrier to the entry of phytopathogens. With respect to Si accumulation, tomato is classified as a non-accumulator (an excluder), similarly to other members of the nightshade family, such as tobacco. Despite the low capacity of accumulating Si, when supplied to tomato plants, the metalloid improves growth under (a)biotic stress conditions, e.g., by enhancing the yield of fruits or by improving vegetative growth through the modulation of physiological parameters. In light of the benefits of Si in crop protection, the available literature data on the effects of this metalloid in mitigating salt stress in tomato are reviewed with a perspective on its use as a biostimulant, boosting the production of fruits as well as their post-harvest stability. Full article
(This article belongs to the Special Issue Recent Advances and Applications of Biostimulants for Plant Growth Promotion and Environmental Stress Adaptation)
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