Plants — Open Access Journal

Root hairs often contribute to nutrient uptake from environments, but the contribution varies among nutrients. In Arabidopsis, two high-affinity sulfate transporters, SULTR1;1 and SULTR1;2, are responsible for sulfate uptake by roots. Their increased expression under sulfur deficiency (−S) stimulates sulfate uptake. Inspired by the higher and lower expression, respectively, of SULTR1;1 in mutants with more (werwolf [wer]) and fewer (caprice [cpc]) root hairs, we examined the contribution of root hairs to sulfate uptake. Sulfate uptake rates were similar among plant lines under both sulfur sufficiency (+S) and −S. Under −S, the expression of SULTR1;1 and SULTR1;2 was negatively correlated with the number of root hairs. These results suggest that both −S-induced SULTR expression and sulfate uptake rates were independent of the number of root hairs. In addition, we observed (1) a negative correlation between primary root lengths and number of root hairs and (2) a greater number of root hairs under −S than under +S. These observations suggested that under both +S and −S, sulfate uptake was influenced by the root biomass rather than the number of root hairs. Full article

In this study, different standard frequency analysis (FA) methods are applied to measured leaf temperature data of maize plants (developmental stages EC13–15). These FA methods are used to identify specific behaviors, regularities, and sudden changes in frequencies/amplitudes of data, e.g., in control engineering. The thorough application of different FA methods in plant studies is novel. The aim of this paper is to analyze features of the measured data and to explore the explanatory power of different methods for the detection of plant dynamic behavioral changes. The basic assumption is an expected relation between plant water stress and resulting changes in leaf temperature oscillations caused by stress-induced changes in stomatal behavior. Therefore, an irrigation experiment (laboratory; controlled environmental conditions) was implemented to compare leaf temperature behavior of stressed and unstressed plants. Leaf temperature time series are processed and the results are compared as functions of time showing the behavioral changes in terms of the different methods applied. The analysis of results is explained; conclusions, which can be made based on different methods, are given. The study confirms the applicability of FA methods and provides new insights into leaf temperature behavioral patterns. Results are discussed regarding the hypothesized incipience of leaf temperature oscillations due to water stress. Full article

The impact of plant-derived smoke as a promoter of seed germination in many crops is well documented. However, very little is known about (1) the appropriate plant species for smoke-water preparation, (2) the effect of smoke-water on the germination and the post-germination parameters in non-fire-prone environments, and (3) the relative importance of dark and light conditions and their possible effects. To fill these gaps in knowledge, we conducted field experiments to evaluate the effect of smoke-water produced from five plant species—white willow, sage, rice straw, rosemary, and lemon eucalyptus—on the germination and seedling growth of cucumber, tomato, scotch marigold, and gladiolus. The seeds and cormels were soaked in smoke-water under light or dark conditions. The results revealed that the smoke-water treatments derived from white willow and lemon eucalyptus enhanced germination, post-germination parameters, and macro element content whilst also contributing to dormancy-breaking. In addition, these smoke-water treatments significantly reduced abscisic acid content and increased α-amylase activity under light conditions; however, the stimulating effects were absent under dark conditions. In conclusion, we provide new evidence that germination and seedling growth in non-fire-prone environments can be enhanced by plant-derived smoke, and that stimulating impacts depend on the plant species used to prepare the smoke-water. Full article

Plant root system architecture changes drastically in response to availability of macronutrients in the soil environment. Despite the importance of root sulfur (S) uptake in plant growth and reproduction, molecular mechanisms underlying root development in response to S availability have not been fully characterized. We report here on the signaling module composed of the CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION (CLE) peptide and CLAVATA1 (CLV1) leucine-rich repeat receptor kinase, which regulate lateral root (LR) development in Arabidopsis thaliana upon changes in S availability. The wild-type seedlings exposed to prolonged S deficiency showed a phenotype with low LR density, which was restored upon sulfate supply. In contrast, the clv1 mutant showed a higher daily increase rate of LR density relative to the wild-type under prolonged S deficiency, which was diminished to the wild-type level upon sulfate supply, suggesting that CLV1 directs a signal to inhibit LR development under S-deficient conditions. CLE2 and CLE3 transcript levels decreased under S deficiency and through CLV1-mediated feedback regulations, suggesting the levels of CLE peptide signals are adjusted during the course of LR development. This study demonstrates a fine-tuned mechanism for LR development coordinately regulated by CLE-CLV1 signaling and in response to changes in S availability. Full article

Plant biofortification with selenium in interaction with the application of an arbuscular mycorrhizal fungi (AMF)-based formulate,with the goal of enhancing Se bioavailability, is beneficial for the development of the environmentally friendly production of functional food with a high content of this microelement. Research was carried out in order to assess the effects of an AMF-based formulate and a non-inoculated control in factorial combination with two selenium treatments with an organic (selenocystine) or inorganic form (sodium selenate) and a non-treated control on the yield, quality, antioxidant properties, and elemental composition of shallot (Allium cepa L. Aggregatum group). Selenocystine showed the best effect on the growth and yield of mycorrhized plants, whereas sodium selenate was the most effective on the non-inoculated plants. The soluble solids, total sugars, monosaccharides, titratable acidity, and proteins attained higher values upon AMF inoculation. Sodium selenate resulted in higher soluble solids, total sugars and monosaccharide content, and titratable acidity than the non-treated control, and it also resulted in higher monosaccharides when compared to selenocystine; the latter showed higher protein content than the control. Calcium, Na, S, and Cl bulb concentrations were higher in the plants inoculated with the beneficial microorganisms. Calcium and sodium concentrations were higher in the bulbs of plants treated with both the selenium forms than in the control. Selenocystine-treated plants showed enhanced accumulation of sulfur and chlorine compared to the untreated plants. The AMF inoculation increased the bulb selenium content by 530%, and the Se biofortification with selenocystine and sodium selenate increased this value by 36% and 21%, respectively, compared to control plants. The AMF-based formulate led to increases in ascorbic acid and antioxidant activity when compared to the non-inoculated control. The bulb ascorbic acid was increased by fortification with both selenium forms when compared to the non-treated control. The results of our investigation showed that both AMF and selenium application represent environmentally friendly strategies to enhance the overall yield and quality performances of shallot bulbs, as well as their selenium content. Full article

A Pomegranate Peel Extract (PGE) has been proposed as a natural antifungal substance with a wide range of activity against plant diseases. Previous studies showed that the extract has a direct antimicrobial activity and can elicit resistance responses in plant host tissues. In the present study, the transcriptomic response of orange fruit toward PGE treatments was evaluated. RNA-seq analyses, conducted on wounded fruits 0, 6, and 24 h after PGE applications, showed a significantly different transcriptome in treated oranges as compared to control samples. The majority (273) of the deferentially expressed genes (DEGs) were highly up-regulated compared to only 8 genes that were down-regulated. Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis showed the involvement of 1233 gene ontology (GO) terms and 35 KEGG metabolic pathways. Among these, important defense pathways were induced and antibiotic biosynthesis was the most enriched one. These findings may explain the underlying preventive and curative activity of PGE against plant diseases. Full article

Differences in coloration exist among red pear cultivars. Here, we selected six red pear cultivars with different genetic backgrounds to elucidate the characteristics of fruit pigmentation. We detected anthocyanin contents and the expression levels of anthocyanin synthesis-related genes in these cultivars at different stages of fruit development. The anthocyanin contents of all six cultivars showed a rise–drop tendency. Principal component and hierarchical cluster analyses were used to distinguish the types of cultivars and the genes crucial to each anthocyanin accumulation pattern. The six cultivars were divided into three groups. Red Zaosu were clustered into one group, Red Sichou and Starkrimson into another group, and Palacer, Red Bartlett, and 5 Hao clustered into a third group. The expression levels of F3H, UFGT2, MYB10, and bHLH3 were similar among the differential coloration patterns of the six cultivars, suggesting a critical and coordinated mechanism for anthocyanin synthesis. Anthocyanin transporters (GST) and light-responsive genes, such as COP1, PIF3.1, and PIF3.2 played limited roles in the regulation of anthocyanin accumulation. This study provides novel insights into the regulation of anthocyanins synthesis and accumulation in red pears. Full article

Of the five polyamine oxidases in Arabidopsis thaliana, AtPAO5 has a substrate preference for the tetraamine thermospermine (T-Spm) which is converted to triamine spermidine (Spd) in a back-conversion reaction in vitro. A homologue of AtPAO5 from the lycophyte Selaginella lepidophylla (SelPAO5) back-converts T-Spm to the uncommon polyamine norspermidine (NorSpd) instead of Spd. An Atpao5 loss-of-function mutant shows a strong reduced growth phenotype when growing on a T-Spm containing medium. When SelPAO5 was expressed in the Atpao5 mutant, T-Spm level decreased to almost normal values of wild type plants, and NorSpd was produced. Furthermore the reduced growth phenotype was cured by the expression of SelPAO5. Thus, a NorSpd synthesis pathway by PAO reaction and T-Spm as substrate was demonstrated in planta and the assumption that a balanced T-Spm homeostasis is needed for normal growth was strengthened. Full article

Nitrogen (N) is one of the essential macronutrients that plays an important role in plant growth and development. Unfortunately, low utilization rate of nitrogen has become one of the main abiotic factors affecting crop growth. Nevertheless, little research has been done on the molecular mechanism of wheat seedlings resisting or adapting to low nitrogen environment. In this paper, the response of wheat seedlings against low nitrogen stress at phenotypic changes and gene expression level were studied. The results showed that plant height, leaf area, shoot and root dry weight, total root length, and number under low nitrogen stress decreased by 26.0, 28.1, 24.3, 38.0, 41.4, and 21.2 percent, respectively compared with plants under normal conditions. 2265 differentially expressed genes (DEGs) were detected in roots and 2083 DEGs were detected in leaves under low nitrogen stress (N-) compared with the control (CK). 1688 genes were up-regulated and 577 genes were down-regulated in roots, whilst 505 genes were up-regulated and 1578 were down-regulated in leaves. Among the most addressed Gene Ontology (GO) categories, oxidation reduction process, oxidoreductase activity, and cell component were mostly represented. In addition, genes involved in the signal transduction, carbon and nitrogen metabolism, antioxidant activity, and environmental adaptation were highlighted. Our study provides new information for further understanding the response of wheat to low nitrogen stress. Full article

: Postharvest diseases significantly reduce the shelf-life of harvested fruits/vegetables worldwide. Bacillus spp. are considered to be an eco-friendly and bio-safe alternative to traditional chemical fungicides/bactericides due to their intrinsic ability to induce native anti-stress pathways in plants. This review compiles information from multiple scientific databases (Scopus, ScienceDirect, GoogleScholar, ResearchGate, etc.) using the keywords “postharvest diseases”, “Bacillus”, “Bacillus subtilis”, “biocontrol”, “storage”, “losses”, and “fruits/vegetables”. To date, numerous examples of successful Bacillus spp. application in controlling various postharvest-emerged pathogens of different fruits/vegetables during handling, transportation, and storage have been described in the literature. The mechanism/s of such action is/are still largely unknown; however, it is suggested that they include: i) competition for space/nutrients with pathogens; ii) production of various bio-active substances with antibiotic activity and cell wall-degrading compounds; and iii) induction of systemic resistance. With that, Bacillus efficiency may depend on various factors including strain characteristics (epiphytes or endophytes), application methods (before or after harvest/storage), type of pathogens/hosts, etc. Endophytic B.subtilis-based products can be more effective because they colonize internal plant tissues and are less dependent on external environmental factors while protecting cells inside. Nevertheless, the mechanism/s of Bacillus action on harvested fruits/vegetables is largely unknown and requires further detailed investigations to fully realize their potential in agricultural/food industries. Full article

Eight selected wild vegetables from Nepal (Alternanthera sessilis, Basella alba, Cassia tora, Digera muricata, Ipomoea aquatica, Leucas cephalotes, Portulaca oleracea and Solanum nigrum) were investigated for their antioxidative potential using 2,2-dyphenyl-1-picrylhydrazyl (DPPH) scavenging, hydrogen peroxide (H₂O₂), ferric reducing antioxidant power (FRAP), and ferric thiocyanate (FTC) methods. Among the selected plant extracts C. tora displayed the highest DPPH radical scavenging activity with an IC₅₀ value 9.898 μg/mL, whereas A. sessilis had the maximum H₂O₂ scavenging activity with an IC₅₀ value 16.25 μg/mL—very close to that of ascorbic acid (16.26 μg/mL). C. tora showed the highest absorbance in the FRAP assay and the lowest lipid peroxidation in the FTC assay. A methanol extract of A. sessilis resulted in the greatest phenolic content (292.65 ± 0.42 mg gallic acid equivalent (GAE)/g) measured by the Folin–Ciocalteu reagent method, while the smallest content was recorded for B. alba (72.66 ± 0.46 GAE/g). The greatest flavonoid content was observed with extracts of P. oleracea (39.38 ± 0.57 mg quercetin equivalents (QE)/g) as measured by an aluminium chloride colorimetric method, while the least was recorded for I. aquatica (6.61 ± 0.42 QE/g). There was a strong correlation between antioxidant activity with total phenolic (DPPH, R² = 0.75; H₂O₂, R² = 0.71) and total flavonoid content (DPPH, R² = 0.84; H₂O₂, R² = 0.66). This study demonstrates that these wild edible leafy plants could be a potential source of natural antioxidants. Full article

Plants take up sulfur (S), an essential element for all organisms, as sulfate, which is mainly attributed to the function of SULTR1;2 in Arabidopsis. A disruption mutant of SULTR1;2, sel1-10, has been characterized with phenotypes similar to plants grown under sulfur deficiency (−S). Although the effects of −S on S metabolism were well investigated in seedlings, no studies have been performed on mature Arabidopsis plants. To study further the effects of −S on S metabolism, we analyzed the accumulation and distribution of S-containing compounds in different parts of mature sel1-10 and of the wild-type (WT) plants grown under long-day conditions. While the levels of sulfate, cysteine, and glutathione were almost similar between sel1-10 and WT, levels of glucosinolates (GSLs) differed between them depending on the parts of the plant. GSLs levels in the leaves and stems were generally lower in sel1-10 than those in WT. However, sel1-10 seeds maintained similar levels of aliphatic GSLs to those in WT plants. GSL accumulation in reproductive tissues is likely to be prioritized even when sulfate supply is limited in sel1-10 for its role in S storage and plant defense. Full article

The Arabidopsis root is a dynamic system where the interaction between different plant hormones controls root meristem activity and, thus, organ growth. In the root, a characteristic graded distribution of the hormone auxin provides positional information, coordinating the proliferating and differentiating cell status. The hormone cytokinin shapes this gradient by positioning an auxin minimum in the last meristematic cells. This auxin minimum triggers a cell developmental switch necessary to start the differentiation program, thus, regulating the root meristem size. To position the auxin minimum, cytokinin promotes the expression of the IAA-amido synthase group II gene GH3.17, which conjugates auxin with amino acids, in the most external layer of the root, the lateral root cap tissue. Since additional GH3 genes are expressed in the root, we questioned whether cytokinin to position the auxin minimum also operates via different GH3 genes. Here, we show that cytokinin regulates meristem size by activating the expression of GH3.5 and GH3.6 genes, in addition to GH3.17. Thus, cytokinin activity provides a robust control of auxin activity in the entire organ necessary to regulate root growth. Full article

The aim of this study was to investigate the different combinations of red (R) and blue (B) light emitting diode (LEDs’) lighting effects on growth, pigment content, and antioxidant capacity in lettuce, spinach, kale, basil, and pepper in a growth chamber. The growth chamber was equipped with R and B light percentages based on total light intensity: 83% R + 17% B; 91% R + 9% B; 95% R + 5% B; and control was 100% R. The photosynthetic photon flux density (PPFD), photoperiod, temperature, and relative humidity of the growth chamber were maintained at 200 ± 5 μmol m⁻² s⁻¹, 16 h, 25/21 ± 2.5 °C, and 65 ± 5%, respectively. It is observed that the plant height of lettuce, kale, and pepper was significantly increased under 100% R light, whereas the plant height of spinach and basil did not show any significant difference. The total leaf number of basil and pepper was significantly increased under the treatment of 95% R + 5% B light, while no significant difference was observed for other plant species in the same treatment. Overall, the fresh and dry mass of the studied plants was increased under 91% R + 9% B and 95% R + 5% B light treatment. The significantly higher flower and fruit numbers of pepper were observed under the 95% R + 5% B treatment. The chlorophyll a, chlorophyll b, and total chlorophyll content of lettuce, spinach, basil, and pepper was significantly increased under the 91% R + 9% B treatment while the chlorophyll content of kale was increased under the 95% R + 5% B light treatment. The total carotenoid content of lettuce and spinach was higher in the 91% R + 9% B treatment whereas the carotenoid content of kale, basil, and pepper was increased under the 83% R + 17% B treatment. The antioxidant capacity of the lettuce, spinach, and kale was increased under the 83% R + 17% B treatment while basil and pepper were increased under the 91% R + 9% B treatment. This result indicates that the addition of B light is essential with R light to enhance growth, pigment content, and antioxidant capacity of the vegetable plant in a controlled environment. Moreover, the percentage of B with R light is plant species dependent. Full article

It has been widely observed that recent increases in atmospheric CO₂ concentrations have had, so far, a positive effect on the growth of plants. This is not surprising since CO₂ is an important nutrient for plant matter, being directly involved in photosynthesis. However, it is also known that the conditions which have accompanied this increase in atmospheric CO₂ concentration have also had significant effects on other environmental factors. It is possible that these other effects may emerge as limiting factors which could act to prevent plant growth. This may involve complex interactions between prevailing sunlight and water conditions, variable temperatures, the availability of essential nutrients and the type of synthetic pathway for the plant species. The issue of concern to this investigation is if we should be worried about a possible shift in the C₃-C₄ paradigm driven by changes in the atmospheric CO₂ concentration, or if some other factor, such as water scarcity, is much more relevant within a 30-year time frame. If an opinion is needed on what will have the worst effect on the survival of the planet between the scarcity of water or the reduced efficiency of C₃ plants to sequester CO₂, the issue of water is the more incisive. Full article

The main objective of this study was to evaluate the genetic diversity and agricultural significance of bacterial communities associated with the surfaces of selected agronomic plants (carrot, cabbage and turnip). The bacterial diversity of fresh agricultural produce was targeted to identify beneficial plant microflora or opportunistic human pathogens that may be associated with the surfaces of plants. Bacterial strains were screened in vitro for auxin production, biofilm formation and antibiotic resistance. 16S rRNA gene sequencing confirmed the presence of several bacterial genera including Citrobacter, Pseudomonas, Pantoea, Bacillus, Kluyvera, Lysinibacillus, Acinetobacter, Enterobacter, Serratia, Staphylococcus, Burkholderia, Exiguobacterium, Stenotrophomonas, Arthrobacter and Klebsiella. To address the biosafety issue, the antibiotic susceptibility pattern of strains was determined against different antibiotics. The majority of the strains were resistant to amoxicillin (25 µg) and nalidixic acid (30 µg). Strains were also screened for plant growth-promoting attributes to evaluate their positive interaction with colonized plants. Maximum auxin production was observed with Stenotrophomonas maltophilia MCt-1 (101 µg mL⁻¹) and Bacillus cereus PCt-1 (97 µg mL⁻¹). Arthrobacter nicotianae Lb-41 and Exiguobacterium mexicanum MCb-4 were strong biofilm producers. In conclusion, surfaces of raw vegetables were inhabited by different bacterial genera. Potential human pathogens such as Bacillus cereus, Bacillus anthracis, Enterobacter cloacae, Enterobacter amnigenus and Klebsiella pneumoniae were also isolated, which makes the biosafety of these vegetable a great concern for the local community. Nevertheless, these microbes also harbor beneficial plant growth-promoting traits that indicated their positive interaction with their host plants. In particular, bacterial auxin production may facilitate the growth of agronomic plants under natural conditions. Moreover, biofilm formation may help bacteria to colonize plant surfaces to show positive interactions with host plants. Full article

The effects of the quality and intensity of night interruption light (NIL) on the flowering and morphogenesis of kalanchoe (Kalanchoe blossfeldiana) ‘Lipstick’ and ‘Spain’ were investigated. Plants were raised in a closed-type plant factory under 250 μmol·m⁻²·s⁻¹ PPFD white light emitting diodes (LEDs) with additional light treatments. These treatments were designated long day (LD, 16 h light, 8 h dark), short day (SD, 8 h light, 16 h dark), and SD with a 4 h night interruption (NI). The NIL was constructed from 10 μmol·m⁻²·s⁻¹ or 20 μmol·m⁻²·s⁻¹ PPFD blue (NI-B), red (NI-R), white (NI-W), or blue and white (NI-BW) LEDs. In ‘Spain’, the SPAD value, area and thickness of leaves and plant height increased in the NI treatment as compared to the SD treatment. In ‘Lipstick’, most morphogenetic characteristics in the NI treatment showed no significant difference to those in the SD treatment. For both cultivars, plants in SD were significantly shorter than those in other treatments. The flowering of Kalanchoe ‘Lipstick’ was not affected by the NIL quality, while Kalanchoe ‘Spain’ flowered when grown in SD and 10 μmol·m⁻²·s⁻¹ PPFD NI-B. These results suggest that the NIL quality and intensity affect the morphogenesis and flowering of kalanchoe, and that different cultivars are affected differently. There is a need to further assess the effects of the NIL quality and intensity on the morphogenesis and flowering of short-day plants for practical NIL applications. Full article

In the last decade, several studies have relied on a small number of plastid genomes to deduce deep phylogenetic relationships in the species-rich Myrtaceae. Nevertheless, the plastome of Rhodomyrtus tomentosa, an important representative plant of the Rhodomyrtus (DC.) genera, has not yet been reported yet. Here, we sequenced and analyzed the complete chloroplast (CP) genome of R. tomentosa, which is a 156,129-bp-long circular molecule with 37.1% GC content. This CP genome displays a typical quadripartite structure with two inverted repeats (IRa and IRb), of 25,824 bp each, that are separated by a small single copy region (SSC, 18,183 bp) and one large single copy region (LSC, 86,298 bp). The CP genome encodes 129 genes, including 84 protein-coding genes, 37 tRNA genes, eight rRNA genes and three pseudogenes (ycf1, rps19, ndhF). A considerable number of protein-coding genes have a universal ATG start codon, except for psbL and ndhD. Premature termination codons (PTCs) were found in one protein-coding gene, namely atpE, which is rarely reported in the CP genome of plants. Phylogenetic analysis revealed that R. tomentosa has a sister relationship with Eugenia uniflora and Psidium guajava. In conclusion, this study identified unique characteristics of the R. tomentosa CP genome providing valuable information for further investigations on species identification and the phylogenetic evolution between R. tomentosa and related species. Full article

Frankincense, the oleo-gum-resin of Boswellia trees, has been an important religious and medicinal element for thousands of years, and today is used extensively for essential oils. One of the most popular frankincense species is Boswellia sacra Flueck. (syn. Boswellia carteri Birdw.) from Somalia and Somaliland. Recent increases in demand have led to many areas being overharvested, emphasizing the need for incentives and monitoring for sustainable harvesting, such as certification schemes. Concurrently, a new chemical component, called methoxydecane, has emerged in oils claimed to be B. carteri, suggesting the possibility of a chemical marker of overharvesting or other stress that could aid in monitoring. To find the source of this new chemical component, we sampled resin directly from trees in areas producing the new methoxydecane chemotype. This revealed that methoxydecane comes not from Boswellia carteri, but from a newly described frankincense species, Boswellia occulta. The presence of Boswellia occulta oil in essential oil sold as pure B. carteri, including certified organic oil, emphasizes the current lack of traceability in the supply chain and the ineffectiveness of organic certification to secure purity and sustainable harvesting in wildcrafted species. Full article