In cellular circumstances where carbohydrates are scarce, plants can use alternative substrates for cellular energetic maintenance. In plants, the main protein reserve is present in the chloroplast, which contains most of the total leaf proteins and represents a rich source of nitrogen and amino acids. Autophagy plays a key role in chloroplast breakdown, a well-recognized symptom of both natural and stress-induced plant senescence. Remarkably, an autophagic-independent route of chloroplast degradation associated with Chloroplast Vesiculation (CV) gene was recently demonstrated. During extended darkness, CV is highly induced in the absence of autophagy, contributing to the early senescence phenotype of atg mutants. To further investigate the role of CV under dark-induced senescence conditions, mutants with low expression of CV ( amircv) and double mutants amircv1xatg5 were characterized. Following darkness treatment, no aberrant phenotypes were observed in amircv single mutants; however, amircv1xatg5 double mutants displayed early senescence and enhanced dismantling of chloroplast and membrane structures under these conditions. Metabolic characterization revealed that the functional lack of both CV and autophagy leads to higher impairment of amino acid release and differential organic acid accumulation during starvation conditions. The data obtained are discussed in the context of the role of CV and autophagy, both in terms of cellular metabolism and the regulation of chloroplast degradation.

The 18O enrichment (Δ 18O) of leaf water affects the Δ 18O of photosynthetic products such as sucrose, generating an isotopic archive of plant function and past climate. However, uncertainty remains regarding how leaf water compartmentation between photosynthetic and non-photosynthetic tissue affects the relationship between Δ 18O of bulk leaf water (Δ 18O LW) and leaf sucrose (Δ 18O Sucrose). We grew Lolium perenne (a C 3 grass) in mesocosm-scale, replicated experiments with daytime relative humidity (RH 50 or 75%) and CO 2 level (200, 400 or 800 μmol mol -1) as factors, and determined Δ 18O LW, Δ 18O Sucrose and morpho-physiological leaf parameters, including transpiration ( E leaf), stomatal conductance ( g s) and mesophyll conductance to CO 2 ( g m). The Δ 18O of photosynthetic medium water (Δ 18O SSW) was estimated from Δ 18O Sucrose and the equilibrium fractionation between water and carbonyl groups (ε bio). Δ 18O SSW was well predicted by theoretical estimates of leaf water at the evaporative site (Δ 18O e) with adjustments that correlated with gas exchange parameters ( g s or total conductance to CO 2). Isotopic mass balance and published work indicated that non-photosynthetic tissue water was a large fraction (~0.53) of bulk leaf water. Δ 18O LW was a poor proxy for Δ 18O Sucrose, mainly due to opposite Δ 18O responses of non-photosynthetic tissue water (Δ 18O non-SSW) relative to Δ 18O SSW, driven by atmospheric conditions.

A key to achieve the goals put forward in the UN's 2030 Agenda for Sustainable Development, it will need transformative change to our agrifood systems. We must mount to the global challenge to achieve food security in a sustainable manner in the context of climate change, population growth, urbanization, and depletion of natural resources. Rice is one of the major staple cereal crops that has contributed, is contributing, and will still contribute to the global food security. To date, rice yield has held pace with increasing demands, due to advances in both fundamental and biological studies, as well as genomic and molecular breeding practices. However, future rice production depends largely on the planting of resilient cultivars that can acclimate and adapt to changing environmental conditions. This Special Issue highlight with reviews and original research articles the exciting and growing field of rice-environment interactions that could benefit future rice breeding. We also outline open questions and propose future directions of 2050 rice research, calling for more attentions to develop environment resilient rice especially hybrid rice, upland rice and perennial rice.

The thylakoid membrane is in a temperature-sensitive equilibrium that shifts repeatedly during the life cycle in response to ambient temperature or solar irradiance. Plants respond to seasonal temperature by changing their thylakoid lipid composition, while a more rapid mechanism for short-term heat exposure is required. The emission of the small organic molecule isoprene has been postulated as one such possible rapid mechanism. The protective mechanism of isoprene is not known, but some plants emit isoprene during periods of high-temperature stress. In this work, we investigate the dynamics and structure for lipids within a thylakoid membrane at different temperatures and varied isoprene content using classical molecular dynamics simulations. The results are compared with experimental findings from across the literature for temperature-dependent changes in the lipid composition and shape of thylakoids. We find that the surface area, volume, and flexibility of the membrane, as well as the lipid diffusion, increase with temperature, while the membrane thickness decreases. Saturated thylakoid 34:3 glycolipids derived from eukaryotic synthesis pathways exhibit significantly different dynamics than lipids from prokaryotic synthesis paths, which could explain the upregulation of specific lipid synthesis pathways at different temperatures. Increasing isoprene concentration was not observed to have a significant thermoprotective effect on the thylakoid membranes, and that isoprene readily permeated the membrane models tested here.

Plants perceive environmental stresses as whole organisms via distant signals conveying danger messages through their vasculature. In parallel to vascular transport, airborne plant volatile compounds, including green leaf volatiles (GLVs), can bypass the lack of vascular connection. However, some small volatile compounds move through the vasculature; such vascular transport is little known about GLVs. Here we illustrate GLV alcohols as solutes move within xylem vessels in Zea mays. We describe GLV alcohols, including Z-3-hexenol and its isomer E-3-hexenol, which is not synthesized in maize, is mobilized through the transpiration stream via xylem vessels. Since transpiration is mediated by stomatal aperture, closing stomata by two independent methods diminishes the transport of GLV alcohol and its isomer. In addition, lower transport of GLV alcohols impairs their function in inducing terpenoid biosynthesis suggesting xylem transport of GLV alcohols plays a significant role in their systemic function. Our study not only shows that GLV alcohols can be transported in the xylem but points to stomatal regulation as a mechanism that climatic factors such as drought, heat, flooding, and high CO 2 levels affect systemic signaling functions of GLVs.

Brassica crops include various edible vegetable and plant oil crops, and their production is limited by low temperature beyond their tolerant capability. The key regulators of low-temperature resistance in Brassica remain largely unexplored. To identify post-transcriptional regulators of plant response to low temperature, we performed small RNA profiling, and found that 16 known miRNAs were responsive to cold treatment in Brassica rapa. The cold response of seven of those miRNAs were further confirmed by qRT-PCR and/or northern blotting analyses. In parallel, a genome-wide association study of 220 accessions of Brassica napus identified four candidate MIRNA genes, all of which were cold-responsive, at the loci associated with low temperature resistance. Specifically, these large-scale data analyses revealed a link between miR1885 and the plant response to low temperature in both B. rapa and B. napus. Using 5′ rapid amplification of cDNA ends approach, we validated that miR1885 can cleave its putative target transcripts, Bn.TIR.A09 and Bn.TNL.A03, in B. napus. Furthermore, overexpression of miR1885 in Semi-winter type B. napus decreased the mRNA abundance of Bn.TIR.A09 and Bn.TNL.A03, resulting in increased sensitivity to low temperature. Knocking down of miR1885 in Spring type B. napus led to increased mRNA abundance of its targets and improved rapeseed tolerance to low temperature. Together, our results suggested that the loci of miR1885 and its targets could be potential candidates for the molecular breeding of low temperature-tolerant Spring type Brassica crops.

Plants can detect neighbouring plants through a reduction in the ratio between red and far-red light (R:FR). This provides a signal of plant-plant competition and induces rapid plant growth while inhibiting defence against biotic stress, two interlinked responses designated as the shade avoidance syndrome (SAS). Consequently, the SAS can influence plant-herbivore interactions that could cascade to higher trophic levels. However, little is known on how the expression of the SAS can influence tritrophic interactions. We investigated whether changes in R:FR affect the emission of herbivore-induced plant volatiles (HIPVs), and whether these changes influence the attraction of the zoophytophagous predator Macrolophus pygmaeus. We also studied how the expression of the SAS and subsequent inhibition of plant defences affects the reproduction of M. pygmaeus in both the presence and absence of the greenhouse whitefly ( Trialeurodes vaporariorum) as arthropod prey. The results show that changes in R:FR have little effect on HIPV emissions and predator attraction. However, a reduction in R:FR leads to increased reproduction of both the predator and the whiteflies. We conclude that shade avoidance responses can increase the population development of M. pygmaeus directly by reducing plant defences, and indirectly by supporting higher herbivore densities.

Heightened by the COVID-19 pandemic there has been a global increase in urban greenspace appreciation. Indoor plants are equally important for improving mental health and air quality but despite evolving in humid (sub)tropical environments with aerial root types, planting systems ignore aerial resource supply. This study directly compared nutrient uptake preferences of aerial and soil-formed roots of three common houseplant species under high and ambient relative humidities. Growth and physiology parameters were measured weekly for Anthurium andreanum, Epipremnum aureum and Philodendron scandens grown in custom made growth chambers. Both aerial and soil-formed roots were then fed mixtures of nitrate, ammonium and glycine, with one source labelled with 15N to determine uptake rates and maximum capacities. Aerial roots were consistently better at nitrogen uptake than soil roots but no species, root type or humidity condition showed a preference for a particular nitrogen source. All three species grew more in high humidity, with aerial roots demonstrating the greatest biomass increase. Higher humidities for indoor niches, together with fertiliser applications to aerial roots will support indoor plant growth, creating lush calming indoor environments for people inhabitants.

Increasing rice yield has always been one of the primary objectives of rice breeding. However, panicle degeneration, a complex phenomenon regulated by many genetic and environmental factors, often occurs in rice-growing regions and severely curbs rice yield. In this study, we obtained a new apical panicle degeneration mutant named ym48, which induces a marked degeneration rate and diminishes the final grain yield. Cellular and physiological analyses revealed that the apical panicle in ym48 undergoes programmed cell death, accompanied by excessive accumulations of peroxides. Following, the panicle degeneration gene OsCAX1a was identified, which was involved in Ca2+ transport in the ym48 mutant. In OsCAX1a, a relative conserved T to A substitution was noted at the 64th amino acid, which disrupted Ca2+ transport. Hydroponics assays and Ca2+ quantification confirmed that Ca2+ transport and distribution to apical tissues were restricted and over-accumulated in mutant sheath. Ca2+ transport between cytoplasm and vacuole was affected, and the reduced content of Ca2+ in vacuole and cell wall and the decreased of Ca2+ absorption were appeared in ym48 mutant. RNA-Seq data indicated that the abnormal CBL (calcineurin b-like proteins) pathway mediated by deficient Ca2+ might occur in mutant, resulting in the burst of ROS and programmed cell death in panicles. Our results explained the key role of OsCAX1a in Ca2+ transport and distribution and laid a foundation to further explore the genetic and molecular mechanisms of panicle degeneration and the efficiency of Ca2+ fertilization in rice.

CO 2-induced chloroplast movement was reported in the monograph by Gustav Senn in 1908: unilateral CO 2 supply to the one cell-layered moss leaves induced the positively CO 2-tactic periclinal arrangement of chloroplasts. However, from the modern criteria, several experimental settings are unacceptable. Here, using a model moss plant Physcomitrium patens, we examined basic features of chloroplast CO 2-tactic relocation with a modernized experimental system. The CO 2 relocation was light-dependent and especially the CO 2 relocation in red light was substantially dependent on photosynthetic activity. Between the cytoskeletons responsible for chloroplast movement of P. patens, the microfilament mainly worked for CO 2 relocation, but the microtubule-based movement was insensitive to CO 2. The CO 2 relocation was induced not only by air with and without CO 2 but also by the more realistic difference in CO 2 concentration between the two sides. In the leaves placed on the surface of a gel sheet, chloroplasts avoided the gel side and positioned in the air facing surface. This was also shown to be photosynthesis dependent. Based on these observations, we propose a working hypothesis that the threshold light intensity between the light-accumulation and -avoidance responses of the photorelocation would be increased by CO 2, resulting in the CO 2-tactic relocation of chloroplast.

The combined study of C and O isotopes in plant organic matter has emerged as a powerful tool for understanding plant functional responses to environmental change. The approach relies on established relationships between leaf gas exchange and isotopic fractionation to derive a series of model scenarios that can be used to infer changes in photosynthetic assimilation and stomatal conductance driven by changes in environmental parameters (CO2, water availability, air humid-ity, temperature, nutrients). We review the mechanistic basis for a conceptual model, in light of recently published research, and discuss where isotopic observations don’t match our current understanding of plant physiological response to environment. We demonstrate that 1) the mod-el was applied successfully in many, but not all studies, 2), while originally conceived for leaf isotopes, the model has been applied extensively to tree ring isotopes in the context of tree physiology and dendrochronology. Where isotopic observations deviate from physiologically plau-sible conclusions, this mismatch between gas-exchange and isotope response provides valuable insights on underlying physiological processes. Overall, we found that isotope responses can be grouped into situations of increasing resource limitation versus higher resource availability. The dual isotope model helps to interpret plant responses to a multitude of environmental factors.

Stomata are the key nodes linking photosynthesis and transpiration. By regulating the opening degree of stomata, plants successively achieve the balance between water loss and carbon dioxide acquisition. The dynamic behavior of stomata is an important cornerstone of plant adaptability. Though there have been miscellaneous experimental results on stomata and their constituent cells, the guard cells and the subsidiary cells, current theory of stomata regulation is far from clear and unified. In this work, we develop an integrated model to describe the stomatal dynamics of seed plants based on existing experimental results. The model includes three parts: 1) a passive mechanical model of the stomatal aperture as a bivariate function of the guard-cell and the subsidiary-cell turgor pressures; 2) an active regulation model with a targeted ion-content in guard cells as a function of their water potential; and 3) a dynamical model for the movement of potassium ions and water content. Our model has been used to reproduce different experimental phenomena semi and stomatal responses to environment conditions.

Conservative flowering behaviors, such as flowering during long days in summer or late flowering at a high leaf number, are often proposed to protect against variable winter and spring temperatures which lead to frost damage if premature flowering occurs. Yet, due the many factors in natural environments relative to the number of individuals compared, assessing which climate characteristics drive these flowering traits has been difficult. We applied a multidisciplinary approach to ten winter-annual Arabidopsis thaliana populations originating along a wide climactic gradient in Norway. We used a variable reduction strategy to assess which of 100 climate descriptors from their home sites correlated most to their behaviors when grown in common garden and assessed sequence variation of 19 known environmental-response flowering genes. Photoperiod sensitivity inversely correlated with interannual variation in timing of growing season onset (start of favorable spring temperatures). Time to flowering appeared driven by growing season length, curtailed by cold fall temperatures. The distribution of FLM, TFL2, and HOS1 haplotypes, genes involved in ambient temperature response, correlated with growing-season climate. We show that long-day sensitivity and late flowering may be driven not by risk of spring frosts, but by growing season temperature and length perhaps to opportunistically maximize growth.

β-Glucosidase is validated as an elicitor for early immune responses in plants and it was detected in the salivary glands of Frankliniella occidentalis in previous research. Seven differentially expressed genes encoding β-Glucosidase were obtained by comparing the transcriptomes of F. occidentalis adults grown under two different CO 2 concentrations (800 ppm vs. 400 ppm), which might be associated with the differences in the interaction between F. occidentalis adults and its host plant, Phaseolus vulgaris under different CO 2 levels. To verify this speculation, changes in defense responses based on the production and elimination of reactive oxygen species (ROS) in P. vulgaris leaves treated with three levels of β-Glucosidase activity under ambient CO 2 (aCO 2) and elevated CO 2 (eCO 2) were measured in this study. The results showed that both leaves infested with thrips and those sprayed with the pure β-Glucosidase solution showed significant increases in ROS levels under aCO 2 and eCO 2, and the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased correspondingly, while in leaves infested with FoβGlu-1-silenced thrips, the ROS levels and activities of these enzymes did not change significantly during the first 12 hours of injury regardless of CO 2 level. Besides, significantly higher levels of ROS and lower activities of SOD, POD and CAT in injured leaves under eCO 2 compared to aCO 2 were noticed, which would negatively affect P. vulgaris leaves and facilitate thrips damage.

As sessile organisms, plants are constantly challenged by a dynamic growing environment. This includes fluctuations in temperature, water availability, light levels, and atmospheric conditions. In concert with changes in abiotic conditions, plants experience changes in biotic stress pressures, including plant pathogens, viruses, and herbivores. Human-induced increases in atmospheric carbon dioxide (CO 2) levels have led to alterations in plant growth environments that challenge their productivity and nutritional quality. Additionally, it is predicted that climate change will alter the prevalence and virulence of plant pathogens, further challenging plant productivity. A knowledge gap exists in the complex interplay between plant responses to biotic and abiotic stress conditions. Closing this gap is crucial for developing climate resilient crops in the future. Here, we review the physiological responses of plants to elevated CO 2, temperature, tropospheric ozone (O 3), and drought conditions, as well as the interaction of these abiotic stress factors with plant pathogen pressure. Additionally, we describe the crosstalk and trade-offs involved in plant responses to both abiotic and biotic stress, and outline targets for future work to develop a more sustainable future food supply in light of future climate change.

The linkage of stomatal behavior with photosynthetic processes is critical to understanding water and carbon cycles under global change. The slope ( g1) of stomatal conductance ( gs) versus CO 2 assimilation ( Anet) serves as a proxy of the marginal water cost of carbon acquisition and the trade-off between carbon gain and water loss. Here we use g1 to assess species differences in the response of stomatal behavior to experimental climate change manipulations, asking whether generalizable patterns exist across species and climate contexts. A total of 17,727 Anet- gs measurements made in a long-term open-air experiment under ambient and +3.3°C warming, and ambient and ~40% summer rainfall reduction provided > 2,700 estimates of g1 across 21 boreal and temperate tree species. All species became more conservative in their water use (lower g1) in warming and/or reduced rainfall treatments because of lower soil moisture. In contrast to these phenotypic responses, species from warmer and drier habitats tended to have slightly higher g1 and to be the least sensitive to the decrease in soil water. Overall, both warming and rainfall reduction consistently made stomatal behavior more conservative in terms of water loss per unit carbon gain across 21 species and a decade of experimental observation.

Local adaptation is a major driver of biological diversity, and related species may develop analogous (parallel evolution) or alternative (divergent evolution) solutions to similar ecological challenges. We expect these adaptive solutions between closely related organisms would culminate in both phenotypic and genotypic signals. In this study, we employ a reciprocal transplant, glasshouse experiment with two Eucalyptus species ( E. grandis and E. tereticornis) with large, overlapping distributions grown under contrasting ‘local’ temperature conditions (tropic and temperate) to investigate the independent contribution of adaptation, plasticity, and their interaction at molecular, physiological and morphological levels. We find key traits differ in their response. The link between gene expression and traits markedly differed between species. Divergent evolution was the dominant pattern driving adaptation as unique gene responses (91% of all significant genes) was the greatest factor driving differentiation; but overlapping gene (homologous) responses were dependent on the determining factor (plastic, adaptive, or genotype by environment interaction). 98% of the plastic homologs were similarly regulated, while 50% of the adaptive homologs and 100% of the interaction homologs were antagonistically regulated. Therefore, parallel evolution for the adaptive effect in homologous genes was greater than expected but not in favour of divergent evolution. Further, heat shock proteins for E. grandis were almost entirely driven by adaptive responses, while plasticity drove the response in E. tereticornis. These results suggest divergent molecular evolutionary solutions dominated the adaptive mechanisms among species, even in similar ecological circumstances. Thus, trees with overlapping distributions are unlikely to equally persist in the future, suggesting that management of future forests to changing temperature conditions must be species specific.

Group VII Ethylene Response Factors (ERF-VII) are plant-specific transcription factors (TFs) known for their role in the activation of hypoxia-responsive genes under low oxygen stress but also in plant endogenous hypoxic niches. However, their function in the microaerophilic nitrogen-fixing nodules of legumes has not yet been investigated. We investigated regulation and the function of the two Medicago truncatula ERF-VII TFs ( MtERF74 and MtERF75) in roots and nodules, MtERF74 and MtERF75 in response to hypoxia stress and during the nodulation process using an RNA interference strategy and targeted proteolysis of MtERF75. Knockdown of MtERF74 and MtERF75 partially blocked the induction of hypoxia-responsive genes in roots exposed to hypoxia stress. In addition, a significant reduction in nodulation capacity and nitrogen fixation activity was observed in mature nodules of double knockdown transgenic roots. Overall, the results indicate that MtERF74 and MtERF75 are involved in the induction of MtNR1 and Pgb1.1 expression for efficient Phytogb-NO respiration in the nodule.