Environmental and Experimental Botany最新文献

Invasive plants commonly compete with native plants in the introduced range; however, how leaf litter and rhizosphere soil microbes influence the competition between invasive and native plants with varying microbial sources and seedling densities remains to be characterized. In this study, the invasive plant Ageratina adenophora (Asteraceae) and two cooccurring native plant species, Senecio scandens (Asteraceae) and Achyranthes bidentata (Amaranthaceae), were used as experimental plants to test their impacts in a greenhouse. We observed that leaf litter and rhizosphere soil microbes negatively or neutrally impacted invasive or native plant growth when competing. However, microbes enhanced the competitive dominance of A. adenophora over S. scandens but weakened its competitiveness over A. bidentata. Leaf litter microbes were more beneficial for A. adenophora growth and thus made it more competitive than rhizosphere soil microbes when competing with S. scandens. Regardless of the presence or absence of microbes, conspecific inoculation was better for A. adenophora growth and thus enhanced competition dominance more than heterospecific inoculation when competing with A. bidentata. A high seedling density was more beneficial for A. adenophora competition dominance than a low density was when A. adenophora was competing with S. scandens. Nonetheless, the relative competitiveness of A. adenophora was greater than that of the two native species; in particular, A. adenophora had stronger competitive dominance over A. bidentata than over S. scandens. Our data confirmed that the important role of leaf litter microbes in the competition between invasive and native plants cannot be ignored.

Spring cold stress poses a great threat to wheat reproductive growth, leading to compromised spike development and grain yield. There are two types of cold stress i.e. chilling stress (CS, above zero) and freezing stress (FS, below zero). However, it is unclear whether there is a difference in the mechanism of CS and FS in regulating spikelet development. This study aimed to unravel the underlying regulation in determining the difference for wheat spikelet exposed to CS at 2 °C and FS at −2°C by integrative analyses of transcriptome, metabolome, and physiology. Delayed floret development and shrunken cellular morphology in both CS and FS were observed, even malformation and degradation of anther cells occurred in FS. Kyoto Encyclopedia of gene and genomes (KEGG) analyses revealed that the most abundantly enriched pathways are phytohormone biosynthesis, starch and sucrose metabolism, and phenylpropanoid biosynthesis. Further physiological assays related to the identified pathways were performed. Compared to CS, the signal of abscisic acid (ABA), salicylic acid (SA) and jasmonic acid (JA) was more pronounced, and the signal of auxin (IAA) and gibberellin (GA) was inhibited further in FS. In addition, the contents of glucose, fructose and trehalose were elevated in CS, owing to greater activities of cell wall invertase and sucrose synthase, while the hexose content was decreased owing to lower activities of such enzymes in FS, concomitantly, flavonoid barely changed in CS, but it dramatically amounted in FS. Taken together, the glucose and trehalose pathway, along with induced ABA and SA signal were intensified in CS to maintain growth, while greater flavonoid and promoted JA synthesis were induced in FS for cold survival. Understanding the molecular of growth-defense under cold stress would provide a foundation for the development of breeding strategies.

Soybean (Glycine max (L.) Merrill), one of the most valuable crops in the world, faces serious challenges due to drought and insect herbivory. Although well studied independently, we lack a comprehensive understanding of interactive effects of drought × herbivory on both soybean and herbivore traits. A holistic examination of soybean morpho-physiology (above and below-ground traits including root morphology) and herbivore performance can help us understand the potential consequences of these two major stressors on soybean yield and fitness. To this end, we imposed simulated-drought and herbivory by soybean looper (SBL) (Chrysodeixis includens Walker) and assessed both host and herbivore performance. Morpho-physiological traits of soybean including shoot height, chlorophyll content, root morphology, photosynthesis, stomatal conductance, and transpiration were measured. Additionally, growth and feeding behavior of SBL were also assessed to analyze the impacts of drought × herbivory on both host and herbivore. Our results show that certain physiological traits were significantly upregulated under drought × herbivory indicating compensation. We also observed that SBL frass weight, and scale of damage was lower on simulated-drought-experienced plants and, in choice assays, SBL preferred well-watered plants. In addition to lower yields observed under simulated-drought and herbivory interaction, soybeans that experienced both drought and herbivory had the highest number of aborted pods. Our study shows that simulated drought and herbivory have synergistic negative impacts on soybean morpho-physiology and support plant vigor hypothesis. Simulated drought negatively impacted SBL performance and made them less attracted to the soybeans that experienced water stress. Ultimately, the interactive effects of these stressors have negative consequences on soybean yield and fitness. This study demonstrates the need to integrate biotic and abiotic stressors for a better understanding of interactive effects on host and herbivores to make informed decisions for breeding and pest management strategies.

In rice, silicon can mitigate abiotic and biotic stresses. We therefore investigated the effect of Si on key root traits related to soil flooding and salinity tolerance with emphasis on the outer apoplastic barrier and cortical aerenchyma. We tested the hypothesis that Si application alters the phenotypic response of these root traits by growing rice in nutrient solutions without or with Si, designed to mimic drained or flooded soils. We measured the barrier strength through resistance to O₂ and water of the outer parts of adventitious roots along with cortical aerenchyma and other root structural traits. We found that Si delayed the barrier formation and caused lower amounts of inducible cortical aerenchyma. The delay in barrier formation resulted in higher xylem loading of Na⁺ and Cl^-, i.e., the sap flux of both ions was significantly higher for plants with access to Si. The increased ion fluxes correlated with lower lignin and suberin deposition in the outer part of the root. Consequently, we do not recommend using Si application to alleviate combined stress of salinity and soil flooding in rice, since the barrier was more permeable to O₂, and the aerenchyma formation was less pronounced in roots with Si.

The frequency of climate change is increasing globally, which makes predictions challenging. Cold spells during the rice seedling stage can significantly reduce yield, prompting a constant need for cold-tolerant cultivars, which is a major breeding goal. However, the traditional crossbreeding of rice cultivars requires substantial time and effort. Recently, the application of CRISPR/Cas9 to reduce defects in elite cultivars has become a more cost-effective and time-efficient method for breeding cultivars than cross-breeding methods and can alleviate food insecurity. In the present study, CRISPR/Cas9-mediated genome editing was performed for OsCS511 a gene involved in cold susceptibility, identified using quantitative trait loci (QTL) mapping in Ilmi (Oryza sativa L. spp. Japonica cv. Ilmi). In Ilmi, CRISPR/Cas9 tool-edited OsCS511 homozygous lines were used in T₀ and advanced generations in the field. CRISPR/Cas9 induced variations in the DNA sequence and plants with insertions or deletions compared to OsCS511 of Ilmi were selected as genome-edited lines. Agricultural traits, reactive oxygen species scavenging capacity, and stress-tolerance-related gene expression levels were evaluated under normal and cold stress conditions. Under normal conditions, all traits evaluated in the Ilmi and OsCS511 genome-edited lines exhibited similar results; however, when subjected to cold stress, the cold tolerance of OsCS511 genome-edited lines improved or reached the same level as that of Ilmi. OsCS511 genome-edited lines recovered and survived. From a breeding perspective, we suggest that CRISPR/Cas9 technology can precisely reduce defects in existing superior rice cultivars with high efficiency and speed.

Melatonin (MEL) has recently received ample attention as a potential biostimulator in agriculture. MEL has been considered a feasible and effective approach for improving crop output and resilience to various abiotic factors. The first step of MEL biosynthesis in plants is tryptophan (an amino acid), made de novo via the shikimic acid pathway. The processes involved in MEL biosynthesis and plant regulation are described in this review, providing a foundation for understanding the hormone's numerous physiological actions. The research delves into the intricate relationships between MEL and abiotic stresses, such as exposure to drought, salt, heat, cold, and heavy metals. This review provides an overview of recent research on the potential roles of MEL on seed germination, growth, and development in plants, highlighting its benefits for improving crop yield and quality and mitigating the detrimental effects of several abiotic stresses. It also discusses the current understanding of MEL's role as a biostimulator in agriculture, promoting root development, flowering, fruit ripening, and preventing leaf senescence. Furthermore, it summarizes the interplay of MEL with various phytohormones, including cytokinin (CK), auxin (Aux), ethylene (ETH), gibberellic acid (GA), salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), polyamines (PAs), brassinosteroid (BR), and signalling molecules such as NO, H₂O₂, H₂S, and Ca²⁺. MEL shows synergistic interactions with GA, CK, PAs, JA, SA, and BR while exhibiting synergistic and antagonistic regulation with Aux, ETH, and ABA. Also, this review establishes the framework for developing novel MEL-based strategies to enhance agricultural sustainability in the face of increasingly severe environmental conditions.

Salinization has emerged as a worldwide concern hampering the progression of agriculture and husbandry. Arbuscular mycorrhizal (AM) fungi, which abundantly distributed in the Songnen Plain, was considered to possess great potential for combating salinity. To elucidate the relationship between AM fungal community and saline-alkali ecological remediation, a 70-days pot experiment, with the soil in the late succession stage of Songnen saline-alkali habitat was taken as substrate, the dominant plant in the latter as research object, and the rhizosphere soil from three stages as inoculants, was conducted. Simultaneously, Chloris virgate was cultivated to ascertain the accompanying role on mycorrhizal effects and soil improvement. The results revealed that AM fungi effectively regulated the botanical morphogenesis, photosynthesis, osmotic concentration, and antioxidant enzymatic activity under saline-alkali conditions. Specifically, the net photosynthetic rate increased by 1.11–2.44 μmol·(m²)⁻¹·s⁻¹, and the total root length grew by 41.15–148.98 cm after inoculation. Furthermore, the soil salinization and nutrient sequestration were modulated by AM fungi, and that leaded to a notable reduction in soil pH by 0.3 %-1.64 % and an increase in nitrogen content by 52.17 %-118.84 %. In a comprehensive assessment, the utmost ecological advantage appeared in the group inoculated AM fungi procured from the identical stage as the host, with a peak mycorrhizal dependency of 2.93. Additionally, despite enhancing salinization restoration compared to the non-companion group, the associated plants reduced the mycorrhizal dependency of neighbour by a range of 27.04–51.46 %, and significantly decreased the dry weight by 0.09–0.28 g. These results confirmed the occurrence of symbiotic matching phenomenon in saline-alkali habitats and suggested that the mechanism should be considered as utilizing AM fungi for ecological restoration. However, the introduction of companion should be cautious due to their complex effects.

Revealing the spatial-temporal pattern of extreme heat on staple crops is crucial for proposing adaptation strategies to mitigate climate change-related agricultural risks. Studies in this field generally focus on the reproductive stage and rely on a single-staged threshold temperature to construct extreme heat indicators, which particularly neglect the vegetative stage of wheat. Therefore, to measure the extreme heat risks more scientifically across the entire life cycle of wheat, our study defines a new comprehensive extreme heat index (CEHI) that considers specific thresholds in both the reproductive and vegetative stages. In general, under three climate scenarios (RCP2.6, RCP4.5, and RCP8.5), approximately 20 % of the wheat-planting regions in China, especially in winter wheat regions such as the North China Plain, the Sichuan Basin, and the Xinjiang Tarim Basin, are projected to face high levels of extreme heat. Meanwhile, from 2010 to 2099, the average growth rates of extreme heat in China under RCP2.6, RCP4.5, and RCP8.5 scenarios are approximately 0.08, 0.06, and 0.1, respectively. By the century's end, the proportion of wheat-planting regions experiencing high and very high levels (CEHI≥0.4) of extreme heat is projected to increase from 18.0 %, 17.9 %, and 18.4 % to 21.4 %, 25.1 %, and 28.9 % under RCP2.6, RCP4.5, and RCP8.5 scenarios. Among them, RCP8.5 has the highest extreme heat severity on wheat in China, followed by RCP4.5, while RCP2.6 has minimal severity. Under the RCP8.5 scenario, the proportions of very high, high, moderate, low, and very low levels of extreme heat are 3.4 %, 18.5 %, 16.7 %, 14.9 %, and 46.5 %, respectively. Meanwhile, our study also emphasizes that although higher-latitude spring wheat regions will experience a significantly increasing trend in extreme heat, this may not spell long-term damage to wheat. Therefore, with consideration of varied temperature sensitivities across wheat growth stages, our study indicates that CEHI serves as an effective method to comprehensively and scientifically assess extreme heat on wheat. Furthermore, based on the regional and varietal differences in extreme heat under climate change, our study highlights the importance of developing region- and variety-specific policies to ensure the sustainability of wheat.

SQUAMOSA promoter-binding protein-like 3/4/5 (SPL3/4/5) genes are involved mainly in regulating plant flowering through the gibberellin and age pathways. In our previous study, two SPL4-like genes, MiSPL4a and MiSPL4b (MiSPL4a/b), were identified and analyzed in mango, and their highest expression levels were detected in flowers. However, the functions of MiSPL4a and MiSPL4b in mango remain unclear. In this study, bioinformatics, expression, function and interacting proteins were analyzed. The results revealed that MiSPL4a was highly expressed in leaves at the early stage of the flower induction period, while MiSPL4b increased the highest expression peak during the vegetative period. MiSPL4a/b genes were induced by drought treatment. Overexpression of MiSPL4a/b accelerated early flowering and increased the expression levels of several flowering-related genes, such as APETALA1 (AtAP1), FRUITFULL (AtFUL), and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (AtSOC1) in Arabidopsis thaliana. The MiSPL4a/b transgenic plants presented increased resistance to drought and abscisic acid (ABA) treatment, and the MiSPL4b transgenic plants were sensitive to prohexadione-calcium (Pro-Ca) treatment. In addition, MiSPL4a and MiSPL4b interact with MiSOC1, Mi14–3–3, and several stress-related proteins. In summary, these findings indicated that in transgenic Arabidopsis, MiSPL4a/b genes have the function of accelerating flowering and enhancing stress resistance.

Salt stress poses a significant challenge to global food security by hindering crop growth and reducing yields. Nanotechnology holds significant promise for agriculture due to the unique properties of nanoparticles (NPs). Nanopriming, a method involving the soaking of seeds with NPs followed by drying, is gaining popularity for enhancing plant performance under salt stress. Nanopriming, in contrast to other NP application methods like foliar spray or soil application, demands less labor and smaller NP quantities, resulting in cost savings and reduced environmental impact. NPs utilize various mechanisms to penetrate seed coats, including diffusion through intercellular spaces, passage through aquaporins and plasmodesmata, and the formation of pores in cell walls. NPs exert their effects by modulating the level of various phytohormones and expression of genes associated with stress response pathways. NPs enhance seed water absorption, germination rates, production of compatible solutes, mineral uptake, antioxidant defense mechanisms, photosynthetic activity, and regulate ion balance in plants under salt stress. The efficacy of nanopriming is regulated by characteristics of NPs like concentration, size, type, stability, seed characteristics such as size, coat thickness, permeability, and composition, timing of NPs application and the specific plant species involved. Understanding the interaction between NPs and different plant species is essential for tailored nanopriming approaches against salt stress. While nanopriming offers promising solutions to mitigate salt stress and enhance agricultural yields, it is crucial to evaluate NPs characteristics not only for their agricultural efficacy but also for their potential impact on environment and human health.