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Differential transpiration is a newly discovered acclimation strategy of annual plants that mitigates the negative impacts of combined water deficit (WD) and heat stress (HS) on plant reproduction. Under conditions of WD + HS, transpiration of vegetative tissues is suppressed in plants such as soybean and tomato, while transpiration of reproductive tissues is not (termed ‘Differential Transpiration’; DT). This newly identified acclimation process enables the cooling of reproductive organs under conditions of WD + HS, limiting HS‐induced damage to plant reproduction. However, the thresholds at which DT remains active and effectively cools reproductive tissues, as well as the developmental stages at which it is activated in soybean, remain unknown. Here, we report that DT occurs at most nodes (leaf developmental stages) of soybean plants subjected to WD + HS, and that it can function under extreme conditions of WD + HS (i.e.,18% of field water capacity and 42°C combined). Our findings reveal that DT is an effective acclimation strategy that protects reproductive processes from extreme conditions of WD + HS at almost all developmental stages. In addition, our findings suggest that, under field conditions, DT could also be active in plants subjected to low or mild levels of WD during a heat wave. 

An increase in the frequency and intensity of heat waves, floods, droughts and other environmental stresses, resulting from climate change, is threatening agricultural food production worldwide. Heat waves are especially problematic to grain yields, as the reproductive processes of almost all our main grain crops are highly sensitive to heat. At times, heat waves can occur together with drought, high ozone levels, pathogen infection and/or waterlogging stress that suppress the overall process of plant cooling by transpiration. We recently reported that under conditions of heat and water-deficit stress combination, the stomata on sepals and pods of soybean (Glycine max) remain open, while the stomata on leaves close. This process, termed ‘differential transpiration’, enabled the cooling of reproductive organs, while leaf temperature increased owing to suppressed transpiration. In this review article, we focus on the impacts on crops of heat waves occurring in isolation and of heat waves combined with drought or waterlogging stress, address the main processes impacted in plants by these stresses and discuss ways to mitigate the negative effects of isolated heat waves and of heat waves that occur together with other stresses (i.e. stress combination), on crops, with a focus on the process of differential transpiration. This article is part of the theme issue ‘Crops under stress: can we mitigate the impacts of climate change on agriculture and launch the ‘Resilience Revolution’?’. 

Nitric oxide (NO) is a key regulator of plant development, growth, and responses to the environment. Together with hydrogen peroxide (H₂O₂), NO modifies the structure and function of proteins, controlling redox signaling. Although NO has been studied extensively at the cellular and subcellular levels, very little is known about changes in NO content at the whole‐plant level.Here, we report on the development of an aboveground whole‐plant live imaging method for NO. Using mutants with altered NO levels, as well as an NO donor/scavenger, we demonstrate the specificity of the detection method for NO.Arabidopsis thalianaplants were found to produce a basal level of NO under control conditions. NO levels accumulated enzymatically in plants following heat stress applied to the entire plant, as well as in a systemic manner following different locally applied stimuli. Similar or opposing accumulation patterns were also found for NO and H₂O₂during the response of plants to different stimuli.Our findings reveal that NO accumulates during the systemic response of plants to a local stimulus. In addition, they shed new light on the intricate relationships between NO and H₂O₂. The new method reported opens the way for multiple future studies of NO's role in plant biology. 

Abstract Reactive oxygen species (ROS) play a critical role in plant development and stress responses, acting as key components in rapid signalling pathways. The ‘ROS wave’ triggers essential acclimation processes, ultimately ensuring plant survival under diverse challenges. This review explores recent advances in understanding the composition and functionality of the ROS wave within plant cells. During their initiation and propagation, ROS waves interact with other rapid signalling pathways, hormones and various molecular compounds. Recent research sheds light on the intriguing lack of a rigid hierarchy governing these interactions, highlighting a complex interplay between diverse signals. Notably, ROS waves culminate in systemic acclimation, a crucial outcome for enhanced stress tolerance. This review emphasizes the versatility of ROS, which act as flexible players within a network of short‐ and long‐term factors contributing to plant stress resilience. Unveiling the intricacies of these interactions between ROS and various signalling molecules holds immense potential for developing strategies to augment plant stress tolerance, contributing to improved agricultural practices and overall ecosystem well‐being. 

Two plants connected via a Cuscuta bridge exchange rapid systemic calcium, electric, and reactive oxygen species signals, suggesting that Cuscuta may have beneficial effects to host plants. 

Abstract Waterlogging stress (WLS) negatively impacts the growth and yield of crops resulting in heavy losses to agricultural production. Previous studies have revealed that WLS induces a systemic response in shoots that is partially dependent on the plant hormones ethylene and abscisic acid. However, the role of rapid cell-to-cell signaling pathways, such as the reactive oxygen species (ROS) and calcium waves, in systemic responses of plants to WLS is unknown at present. Here, we reveal that an abrupt WLS treatment of Arabidopsis (Arabidopsis thaliana) plants growing in peat moss triggers systemic ROS and calcium wave responses and that the WLS-triggered ROS wave response of Arabidopsis is dependent on the ROS-generating RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD), calcium-permeable channels GLUTAMATE-LIKE RECEPTOR 3.3 and 3.6 (GLR3.3 and GLR3.6), and aquaporin PLASMA MEMBRANE INTRINSIC PROTEIN 2;1 (PIP2;1) proteins. We further show that WLS is accompanied by a rapid systemic transcriptomic response that is evident as early as 10 min following waterlogging initiation, includes many hypoxia-response transcripts, and is partially dependent on RBOHD. Interestingly, the abrupt WLS of Arabidopsis resulted in the triggering of a rapid hydraulic wave response and the transient opening of stomata on leaves. In addition, it induced in plants a heightened state of tolerance to a subsequent submergence stress. Taken together, our findings reveal that the initiation of WLS in plants is accompanied by rapid systemic physiological and transcriptomic responses that involve the ROS, calcium, and hydraulic waves, as well as the induction of hypoxia acclimation mechanisms in systemic tissues. 

Abstract The complexity of environmental factors affecting crops in the field is gradually increasing due to climate change-associated weather events, such as droughts or floods combined with heat waves, coupled with the accumulation of different environmental and agricultural pollutants. The impact of multiple stress conditions on plants was recently termed “multifactorial stress combination” (MFSC) and defined as the occurrence of 3 or more stressors that impact plants simultaneously or sequentially. We recently reported that with the increased number and complexity of different MFSC stressors, the growth and survival of Arabidopsis (Arabidopsis thaliana) seedlings declines, even if the level of each individual stress is low enough to have no significant effect on plants. However, whether MFSC would impact commercial crop cultivars is largely unknown. Here, we reveal that a MFSC of 5 different low-level abiotic stresses (salinity, heat, the herbicide paraquat, phosphorus deficiency, and the heavy metal cadmium), applied in an increasing level of complexity, has a significant negative impact on the growth and biomass of a commercial rice (Oryza sativa) cultivar and a maize (Zea mays) hybrid. Proteomics, element content, and mixOmics analyses of MFSC in rice identified proteins that correlate with the impact of MFSC on rice seedlings, and analysis of 42 different rice genotypes subjected to MFSC revealed substantial genetic variability in responses to this unique state of stress combination. Taken together, our findings reveal that the impacts of MFSC on 2 different crop species are severe and that MFSC may substantially affect agricultural productivity.