Environmental and Experimental Botany最新文献

For adaptation to challenging environments, plants have evolved various response mechanisms, such as inducing the expression of many stress genes, thereby increasing the resistance. Accelerated cell death (ACD) genes have been widely studied in plant senescence and defense responses. However, there are few reports on the role of ACD genes in abiotic stresses in plants. In this experiment, ACD11 was successfully isolated from apples (Malus baccata) and found to be mainly expressed in apple fruits and roots. The response elements of abiotic stresses were also found in the promoter of MbACD11. Furthermore, MbACD11 expression was induced by various abiotic stresses, especially salt treatment. After overexpression of MbACD11 in apple seedlings, callis and Arabidopsis thaliana, all showed enhanced tolerance to salt stress. Under salt conditions, MbACD11-OE showed higher fresh weight and chlorophyll content compared to the WT. It also exhibited lower relative electrical conductivity, malondialdehyde (MDA) content, and reactive oxygen species (ROS) accumulation than the WT. The expression of salt stress-related genes was higher in MbACD11-OE apple seedlings than in WT. In salt stress condition, the apple MbACD11 gene reduced ROS accumulation and affected the expression of salt stress-related genes, hence enhancing tolerance.

Phosphorus-solubilizing bacteria are widely studied for their ability to immobilize heavy metals and promote plant growth. However, previous studies have been focused on the effects of phosphate-solubilizing bacteria on phosphorus release and heavy metal immobilization, and there is a lack of research on the effects of phosphate-solubilizing bacteria on rhizosphere soil bacterial communities and metabolites. In this study, the effects of Klebsiella sp. M2 on wheat rhizosphere microbiome and metabolism were investigated as well as the impact of these changes on wheat absorption of Cd. The results showed that under Cd stress, strain M2 reduced (77.54 %) the content of Cd in culture medium and secreted metabolites involved in plant growth promotion, Cd resistance, and phosphorus solubilization. A pot experiment showed that compared with the control, strain M2 increased (14.3 %-35.9 %) the dry weight and reduced (33.3 %-66.7 %) the content of Cd in wheat grains, straw, and roots. Strain M2 increased the exchangeable Ca, Ca₂-P and Fe-P contents, soil pH, and alkaline phosphatase activity and decreased the acid-extractable Cd content in rhizosphere soil. The increase in Ca concentration had a significant promoting effect on the pH in rhizosphere soil. Moreover, the relative abundances of key bacteria such as Ramlibacter, Microvirga, Pseudarthrobacter, Massilia, Streptomyces, and Paenibacillus increased. Additionally, strain M2 increased the contents of some substances in rhizosphere soil that play an important role in immobilizing Cd and solubilizing phosphorus as well as improving wheat tolerance to Cd. The results showed that inoculation with an exogenous phosphate-solubilizing bacterial strain can result in the activation of key functional bacteria and the regulation of metabolite production in wheat rhizosphere soil to immobilize heavy metals, which has broad potential in the remediation of wheat fields with high heavy metal levels.

Nitrogen availability profoundly impacts crop productivity, especially for soybeans, which exhibit a substantial demand for nitrogen. In response to the over-reliance on nitrogen fertilizers, which poses both inefficiencies and environmental concerns, the potential of melatonin in enhancing nitrogen uptake and utilization in soybeans through root irrigation was investigated. Melatonin significantly increased the activity of ammonium assimilating enzymes, thereby enhancing plant tolerance to low nitrogen levels, particularly at a concentration of 10 μM. This phenomenon has been conclusively linked to the augmented nitrogen fixation and utilization capacity, attributed to the facilitating rhizobial infection. Notably, melatonin influenced flavonoid content, specifically inducing genistein levels, essential for rhizobial infection. The malonyltransferase-encoding gene GmMaT2, which modifies isoflavones, was found to be crucial for the effects of melatonin on nodulation and nitrogen metabolism. The silence of GmMaT2 hindered the beneficial effects of melatonin on nodule development and attenuated its ability to enhance aspects of low nitrogen tolerance in soybean. It was elucidated that the potential of melatonin as a sustainable strategy for enhancing nitrogen utilization efficiency in soybeans. It provided insights into the underlying mechanisms and underscored the significance of GmMaT2 in mediating the beneficial effects induced by melatonin under low nitrogen conditions. The findings present a promising solution for mitigating agricultural costs and environmental impacts.

Light plays a crucial role in seedling de-etiolation, initiating the circadian rhythm, chloroplast development, and autotrophic establishment in plants. Although de-etiolation has been extensively studied in various plant species, the specific regulatory network involved in the light quality effects on seedling de-etiolation in maize remains largely unknown. In this study, we investigated the universal effects of far-red, red, and blue light irradiation on seedling de-etiolation in two maize inbred lines (B73 and Mo17) and their two hybrid genetic backgrounds (B73×Mo17 and Mo17×B73). A sequential increase in the chlorophyll content of maize seedlings was observed during dark-to-light transitions. Intriguingly, 18.56–36.02 % of expressed genes and 61.13–73.02 % of accumulated metabolites were discernibly regulated by different types of light exposure. Co-expression network analysis revealed unique gene regulation patterns in maize seedlings subjected to different light conditions. In darkness, differentially expressed genes were predominantly associated with phenylpropanoid biosynthesis, DNA replication, and DNA repair processes. Far-red light was significantly associated with the circadian rhythm through ZmCCA1 and ZmLHY1 gene expression. Notably, red and blue light activated photosynthesis and glucose metabolism; ZmPIF5.1 emerged as a crucial regulator, upregulating the expression of light-harvesting complex subunits of the photosystem (ZmLHCA1 and ZmLHCB3), chloroplast lipoprotein (ZmCHL), and ribulose-1,5-bisphosphate carboxylases (ZmRbcS1 and ZmRbcS2; i.e., carbon fixation enzymes), thereby facilitating chloroplast development and photosynthesis. This study elucidated the regulatory effects of different light treatments on maize seedling de-etiolation, providing greater understanding of maize growth and flowering in response to various light conditions.

The neotropical palm Mauritia flexuosa produces seeds that show the association between recalcitrance and dormancy. Despite the intolerance to desiccation, the seeds can maintain persistent banks in flooded environment soils (veredas) in the Cerrado biome. As the mechanisms involved in the persistence of recalcitrant seed banks are still poorly understood, the objective of this work was to evaluate the response of M. flexuosa embryos to water deficit and saturation stresses. Embryos of M. flexuosa with water content typical of dispersion or subjected to hydration were exposed to moderate and severe water potentials (Ψ_w= −1.5 MPa and Ψ_w= −2.1 MPa), in addition to water saturation (Ψ_w= 0 MPa). Anatomical, histochemical and ultrastructural evaluations were performed on the embryos after 24 h. Membrane integrity estimation, endo-β-mannanase activity and oxidative stress indicators (H₂O₂ and MDA contents, CAT, SOD and APX activity) were also evaluated. The endosperm structure contributes to the maintenance of embryo hydration, while abundant mucilage reserves favor resilience to desiccation. Post-dispersal hydration makes embryos less vulnerable to oxidative stress, which is due to the non-enzymatic antioxidant system. Both moderate water stress and post-dispersal water absorption induce an increase in metabolism and the mobilization of reserves, which indicate that hydration/dehydration cycles can favor overcoming dormancy. M. flexuosa embryos show resilience to water deficit, and that is crucial for the persistence of seeds in the soil in seasonal environments, however, successful germination is dependent on high hydration, which prevents structural and physiological damage.

The leaf economics spectrum (LES) is an ecophysiological concept that describes the trade-offs between leaf structural and physiological traits. It has been extensively studied across various scales. However, the coordination hypothesis has rarely been tested at the intraspecific scale, especially in crops, for understanding yield increases or predicting evolutionary trajectories. Here, we first tested the relationships among leaf traits and examined the genetic coordination among 209 wheat genotypes. Compared to non-crop grass species, wheat is a fast-growing species, and tends to have a higher value of photosynthetic rate, leaf nitrogen concentration and leaf respiration rate at a given leaf mass per area, although it does align with the predicted direction of the “fast-slow” spectrum. We conducted a principal component analysis (PCA) to compare different traits within wheat. The first axis from PCA (ranging from slow to fast of plant economic investment) is significantly positively associated with the agronomic traits, especially grain yield (R²=0.11, P<0.001). Partially independent changes in leaf nitrogen content and leaf mass per area may allow crops to maximize photosynthetic rates without sacrificing leaf lifespan. The results reveal that some loci are simultaneously associated with different traits, which may be the genetic basis for the formation of trait-trait relationships. The current study deepens the understanding of LES traits in wheat at the intraspecific and genetic levels, supporting the trait-based adaptation strategies to improve wheat productivity and resource-use efficiency.

Water deficit stress largely limits plant growth and survival in natural and managed ecosystems. We studied the morpho-physiological responses of plants associated with distinct strains of Epichloë fungal endophytes to water deficit. We hypothesised that Epichloë symbionts would alleviate the negative effects of water deficit on plants and that both magnitude and mechanisms of endophyte-based alleviation would vary depending on the Epichloë strain. Perennial ryegrass (Lolium perenne) plants from the experimental cultivar GA66 associated with the Epichloë strains AR1, AR5, AR6, and AR37 were subjected to a treatment of sustained water deficit in a pot experiment under controlled growth conditions. We measured plant biomass (shoot and root), water retention, stress-related phytohormones (abscisic acid, jasmonic acid), proline and other water-soluble amino acids, and Epichloë-derived antiherbivore alkaloids. Alleviation of the negative effects of water deficit on plants depended on the Epichloë strain, with AR37 and AR5 providing the greatest protection followed by AR1, while AR6 did not alleviate stress. The AR37-derived water deficit alleviation was associated with enhanced root biomass and plant water retention, and increased concentrations of abscisic acid, proline, and fungal alkaloids. The AR5-derived stress alleviation was associated with enhanced plant water retention and increased proline concentrations, and the AR1-derived alleviation with increased fungal alkaloid concentrations and mycelial biomass. Although AR6 did not alleviate the water deficit, the stress increased Epichloë-derived alkaloid concentrations (and enhanced root biomass) which could provide an advantage for resisting herbivory. Our study highlighted that while Epichloë generally alleviated the effects of water deficit on plants, the mechanisms of stress alleviation varied among associations, and that the host fitness could be increased even in those associations where endophytes did not alleviate direct water deficit stress if herbivores would be present.

Cell wall-associated receptor kinases (WAKs/WAKLs), are a specialized class of plant receptor kinases essential for signaling during stress conditions. However, there has been no report on the involvement of WAKs/WAKLs in salt tolerance in cotton. In this study, we report the functional characterization of GhWAKL26, whose expression is induced by salt, with its levels increasing over time and with higher salt concentrations. In addition, the fusion protein of GhWAKL26 and GFP was localized to the plasma membrane. In transgenic Arabidopsis, the dry weight, fresh weight, and root length were significantly higher than those of wild-type plants, indicating enhanced salt tolerance. While in GhWAKL26-silenced cotton seedlings, H₂O₂, O₂⁻, and MDA content were increased, and chlorophyll content was reduced under salt stress, displaying compromised salt tolerance. RNA-seq analysis revealed that the silencing of GhWAKL26 resulted in the down-regulation of expression levels of certain ion transport-related genes under salt stress, concurrently leading to an increased Na⁺/K⁺ ratio in cotton seedlings. Overall, our findings indicate that GhWAKL26 enhanced plant resistance to salt stress in cotton by regulating the balance of Na⁺ and K⁺ ions.

H₂O₂ is a promising priming agent due to its role in stress-response pathways and in the regulation of gene expression. Several studies have shown that H₂O₂ elicitation improves stress responses. However, information regarding of the intergenerational stress memory of the H₂O₂ priming is limited. Therefore, in this study, we evaluated the stress memory induced by H₂O₂ priming in tobacco plants by testing hydric stress phenotypic response and changes in DNA methylation in the parental priming line and in the next generation. Priming consisted of three foliar applications of 200 mM H₂O₂ every 5 days on 4-week-old plants. DNA methylation profiling was performed by Whole Genome Bisulphite Sequencing (WGBS). Hydric stress challenge consisted of three conditions: control (100 %), moderate (40–45 %) and severe (20–25 %) stress according to the available water field capacity. Plant response to the challenge was evaluated by morphological, biochemical, and molecular attributes. The results showed that H₂O₂ priming displayed a biostimulant effect on vegetative and root development, preventing growth stunting under drought conditions. Plant antioxidant activity was enhanced, as reflected by the decrease in endogenous H₂O₂. In drought conditions, proline content, CAT activity and gene expression of CHS, PIP1 and AQP1 genes were enhanced in the primed-plants (H), their progeny (F1), and the primed-progeny group (FH). DNA methylation profile revealed 795 differentially methylated cytosines (DmCs) in the progeny, with 89 associated with genes involved in cellular response to environmental stimuli. An interaction network highlighted stress response with flavoreductase enzyme as central interaction node, and in the second layer the Repressor of Silencing 1 (ROS1) gene. Thus, the findings suggest that H₂O₂ priming may induce intergenerational memory, presenting a potentially cost-effective strategy in stress management in agriculture.

Functional traits are critical indicators for assessing and predicting plant environmental adaptations and survival strategies. However, less attention has been paid to root functional traits due to the costly and destructive nature of field excavations. This has resulted in a poor understanding of organ trait associations and vegetation survival strategies, particularly for plants in arid environments. In this study, we investigated 11 classical plant functional traits (leaf, stem, and root) and the intact root systems of three dominant coexisting shrubs, Calligonum mongolicum, Nitraria sphaerocarpa, and Haloxylon ammodendron, in a typical oasis–desert ecotone in northwestern China. These three coexisting shrubs generally converge on conservative resource strategies with dimorphic root systems and small leaf mass fractions to cope with strong habitat filtering and survive in arid environments. However, we found significant interspecific divergences in functional traits. Specifically, C. mongolicum had the most conserved traits, the medium root depth (370 cm), and the highest root-shoot ratio (1.72). H. ammodendron had relatively conserved traits, with the most extensive root depth (420 cm, access to groundwater) and the lowest root–shoot ratio (0.45). N. sphaerocarpa had the least conservative traits, the shallowest root depth (200 cm), and the medium root–shoot ratio (1.14). These divergences promote ecological niche segregation and ensure the stable coexistence of shrubs in this resource-limited environment. In contrast to the whole-plant economics spectrum, there was limited coordination between aboveground and belowground functional traits across the three species. Therefore, it is speculated that the different organs of these three species may operate independently to manage different constraints. The deep-rooted H. ammodendron is highly dependent on groundwater; therefore, planting them extensively in the ecotone may increase local groundwater consumption, resulting in the severe degradation of these species, particularly in the context of consecutive oasis expansion and intensified climate change. These results are expected to contribute to the development of effective ecosystem restoration and afforestation practices in such oasis–desert ecotones.