Plant, Cell & Environment最新文献

Photosynthetic organisms utilise the energy of light for the production of photochemical energy, whereas light signals are perceived by photoreceptors to synchronise the cellular processes with environmental conditions. When plants are exposed to excess light, photoprotective mechanisms are activated to tune up light harvesting and dissipation according to the genetic and metabolic capacity of the photosynthetic apparatus. These mechanisms are affected by the growth light composition. Recent evidence suggests that far-red light energy and signalling impose regulatory effects on photoprotective mechanisms. As a result of the exclusion of far-red light from the definition of photosynthetically active radiation, far-red wavelengths remained largely overlooked in photosynthesis research until recently. Nevertheless, current research has unravelled the specific role of far-red spectra in the regulation of several photoprotective mechanisms, which proposes possible links between light perception and photoprotection. In this regard, the review explores and discusses the current scientific understanding of the role of far-red photon energy in redox signalling and photoprotection in plants.

Breeding productive tree genotypes is crucial for sustainable forestry, yet the hydraulic architecture along root-stem-leaf continuum that constrains biomass yield remains unclear. Here, six poplar hybrid genotypes with contrasting yield were used to quantify whole-plant hydraulic resistance, its partitioning patterns, and anatomical traits along the continuum. We observed substantial genetic variations in hydraulic resistance parameters. Roots contributed the largest proportion of whole-plant hydraulic resistance (> 54%). Components along the continuum were well-coordinated, and hydraulic resistance of all components was strongly correlated with yield (R² > 0.75), suggesting that hydraulic resistance is a strong predictor of yield. However, resistance partitioning patterns generally showed weak correlations with yield, with more productive genotypes partitioning a smaller proportion of resistance to leaves. Vessel diameter was a key determinant of hydraulic resistance at the root and leaf levels (R² ≥ 0.75), and vessel length significantly influenced stem hydraulic resistance (R² = 0.80). Additionally, genotypes with higher minor vein density and a lower ratio of palisade to spongy mesophyll thickness exhibited lower leaf resistance. Our results suggest that low hydraulic resistance throughout root-stem-leaf continuum is the functional basis for high yield, and the identification of key hydraulic and structural constraints will help overcome bottlenecks in breeding productive tree genotypes.

The water potential at which leaf cells lose turgor (Ψ_TLP) is a useful predictor of whole-plant drought tolerance and biome wetness. However, many plants can achieve water potential values below Ψ_TLP and recover, raising questions about the physiological processes that occur below Ψ_TLP. We established a controlled greenhouse experiment to induce turgor loss on six shrub species from a Mediterranean-type ecosystem in Southern California and characterised physiological and leaf-structural adjustments to Ψ_TLP. We documented seasonal adjustments in Ψ_TLP, both with and without applied drought. Stomatal closure always occurred below Ψ_TLP, and the margin between the two phenomena increased with lower Ψ_TLP. Drought tolerance was strongly correlated with heat tolerance. Most histological responses to Ψ_TLP involved shrinkage of both spongy mesophyll cells and intercellular air spaces, leading to reduced leaf thickness, but not plasmolysis. Overall, our results indicate a propensity to reach Ψ values far below Ψ_TLP and maintain function for extended periods of time in Southern California shrubs. Whereas species in many ecosystems fall below Ψ_TLP for brief periods of time, the erratic nature of precipitation patterns makes Southern California an outlier in the range of operational plant water potentials.

The symbiosis between nitrogen-fixing rhizobia and plants is considered mutually beneficial, yet its indirect effects on other organisms remain understudied. We examined how rhizobia symbiosis in Phaseolus vulgaris influences the behaviour and performance of Diabrotica balteata larvae. Specifically, we tested larval preference for nodulated (R⁺) vs. non-nodulated (R^-) roots and assessed the impact on larval growth. We also analysed root nutrient content and volatile organic compounds (VOCs) to identify potential chemical cues driving feeding preferences. Larvae strongly preferred R⁺ roots, where they exhibited enhanced growth and higher survival post-metamorphosis. Nutritional analysis revealed that R⁺ roots had greater nutrient content, supporting improved larval performance. VOC profiles differed significantly between treatments, and olfactometer assays confirmed that larval attraction was mediated by VOCs, likely signalling enhanced nutritional benefits from rhizobia symbiosis. Our results demonstrate that rhizobia-induced metabolic changes in bean roots make them more attractive and nutritious to herbivorous larvae. This highlights a complex belowground interaction between nitrogen-fixing bacteria, host plants and herbivores, with potential implications for ecological theory and sustainable agriculture. Understanding these interactions could inform pest management strategies and improve legume cultivation by balancing plant-microbe mutualisms with herbivore dynamics.

Plant reactions to stress vary with development stage and fitness. This study assessed the relationship between light and chilling stress in Arabidopsis acclimation. By analysing the transcriptome and proteome responses of expanding leaves subjected to varying light intensity and cold, 2251 and 2064 early response genes and proteins were identified, respectively. Many of these represent as a yet unknown part of the early response to cold, illustrating a development-dependent response to stress and duality in plant adaptations. While standard light promoted photosynthetic upregulation, plastid maintenance, and increased resilience, low light triggered a unique metabolic shift, prioritizing ribosome biogenesis and lipid metabolism and attenuating the expression of genes associated with plant immunity. The comparison of early response in young leaves with that in expanded ones showed striking differences, suggesting a sacrifice of expanded leaves to support young ones. Validations of selected DEGs in mutant background confirmed a role of HSP90-1, transcription factor FLZ13, and Phospholipase A1 (PLIP) in response to cold, and the PLIP family emerged as crucial in promoting acclimation and freezing stress tolerance. The findings highlight the dynamic mechanisms that enable plants to adapt to challenging environments and pave the way for the development of genetically modified crops with enhanced freezing tolerance.

The antioxidative enzyme monodehydroascorbate reductase (MDHAR) is represented by five genes in Arabidopsis, including four that encode cytosolic and peroxisomal proteins. The in planta importance of these specific isoforms during oxidative stress remain to be characterised. T-DNA mutants for MDAR genes encoding cytosolic and peroxisomal isoforms were studied. To examine their roles in conditions of intracellular oxidative stress, mutants were crossed with a cat2 line lacking the major leaf catalase. Enzyme assays in mdar mutants and of recombinant MDHARs suggest that peroxisomal MDHAR1 and cytosolic MDHAR2 are major players in leaf NADH- and NADPH-dependent activities, respectively. All mutants showed a wild-type phenotype when grown in standard conditions. In the cat2 background, loss of peroxisomal MDHAR functions decreased growth whereas loss of the cytosolic MDHAR2 function had no effect on growth but annulled a large part of transcriptomic and phenotypic responses to oxidative stress. The effects of the mdar2 mutation included decreased salicylic acid accumulation and enhanced glutathione oxidation, and were reverted by complementation with the MDAR2 sequence. Together, the data show that the cytosolic MDHAR2 is dispensable in optimal conditions but essential to promote biotic defence responses triggered by oxidative stress.

Dense planting represents a significant strategy for enhancing soybean yield. However, the shade avoidance response elicited by such planting density may hinder further yield enhancements. To acquire a comprehensive understanding of the spatiotemporal responses of soybean to shading signals, we segmented the shading treatment into three distinct periods and performed transcriptomic analyses on soybean apical tissues, the first internode, hypocotyl, petiole, and leaves during these intervals. Enrichment analysis indicated that hormone signalling networks are substantially modulated by shading signals, predominantly involving hormones such as auxins, gibberellins, and brassinosteroids. Through weighted correlation network analysis and motif enrichment analyses, we identified several gene groups and transcription factors that may be implicated in the shade avoidance response in soybeans. Furthermore, utilizing a transient gene expression system, we validated the functions of key genes, discovering that GmGA20ox, GmUGT73C2, and GmWRKY75c are involved in the regulation of soybean hormone homoeostasis, thereby reinforcing the validity of our analytical findings. This study delineates a transcriptomic framework of soybean responses to shade avoidance, highlighting clusters of essential regulatory genes that govern hormone homoeostasis and plant architecture. The findings provide critical insights for breeding strategies pertinent to dense planting and intercropping systems.

Climate change imposes new constraints on tree survival, emphasising two key parameters: the vapour pressure deficit (VPD) and air temperature. Yet, no study has experimentally evaluated drought-induced tree mortality risk following acclimation to elevated temperatures with low or high VPD. Three tree species of contrasting temperature and drought tolerances (Prunus mahaleb, Quercus robur, and Populus nigra) underwent a growing season of acclimation to elevated temperature and/or VPD, and a lethal drought the following year until stem hydraulic failure was confirmed through micro-CT. Our mechanistic approach to assess temperature and VPD acclimation impacts on drought-induced mortality includes tracking stomatal conductance (g_s), minimum stomatal conductance (g_min), total leaf area (LA_tot), water potential at turgor loss point (Ψ_TLP), and estimating the time to hydraulic failure using modelling. Acclimation to elevated VPD and temperature accelerated stomatal closure, reduced g_min, and raised Ψ_TLP. In contrast, while high temperature reduced g_min, it also increased LA_tot and height. Consequently, hydraulic failure occurred faster in high-temperature-acclimated trees, while it was generally delayed by adding higher VPD. Our findings highlight that the balancing effects of temperature-driven leaf area expansion, which accelerate mortality, and VPD-driven acclimation in stomatal sensitivity, counteract each other, stabilising the timing of mortality.

Photosystem I (PSI) is a central component of photosynthesis, driving essential processes such as light energy conversion and energy metabolism. This review addresses several knowledge gaps regarding PSI by providing comprehensive insights into the structural diversity of PSI supercomplexes across various evolutionary groups, including cyanobacteria, algae and land plants. It clarifies the oligomerization states of PSI and its interactions with light-harvesting complexes (LHCs) and other protein complexes such as NDH and Cyt b₆f. Environmental factors, including light intensity, iron availability and pH, significantly influence PSI's structure and function. These factors drive PSI's adaptability through conformational changes and the formation of specialized supercomplexes. For example, under iron deficiency, cyanobacteria form PSI-IsiA complexes to compensate for reduced PSI content. The diversity of PSI's light-harvesting antenna components, such as Lhca proteins in land plants and Lhcr proteins in red algae, is crucial for optimizing light absorption and energy transfer under varying light conditions. Structural evidence also supports the existence of PSI-PSII supercomplexes, revealing direct interactions that facilitate energy transfer between photosystems and protect them from photodamage. These findings highlight the evolutionary significance of PSI's structural diversity and its role in photosynthetic efficiency and environmental adaptation.