Stomatal density is one of the plant traits influencing leaf gas exchange and is known to be affected by the plant’s environment. Understanding its degree of plasticity to various abiotic factors is therefore important. We conducted a meta-analysis of a wide range of experiments in which plants were grown under different levels of CO₂, light, temperature, and water availability, and derived generalized dose-response curves. Although both stomatal density and stomatal index showed a significant negative correlation with CO₂ levels, these relationships were weak and only marginally consistent across the analyzed experiments. In contrast, the effect of growth light intensity was positive, highly consistent, and substantially stronger than the impact of atmospheric CO₂. Temperature also positively influenced stomatal density, while water availability showed no consistent effects. Based on these dose-response curves, we highlight several caveats when using stomatal density or stomatal index for paleo-CO₂ reconstruction. The weak CO₂ response, coupled with the strong confounding impact of light intensity, poses significant limitations to the accuracy of such estimates.

This paper explores the challenges that arise when performing and interpreting leaf gas exchange measurements in plants subjected to abiotic stress. It highlights how factors such as cuticular fluxes, stomatal closure, and common assumptions about gas exchange can lead to errors, especially under stress conditions. Key phenomena such as substomatal cavity unsaturation and stomatal patchiness during water stress are discussed in detail, as they significantly complicate the calculation of gas exchange parameters under stress. The paper also addresses the importance of other factors, including steady-state conditions, the differences between adaxial and abaxial surface responses, and boundary layer effects, all of which play critical roles in influencing the accuracy of measurements. Important physiological indicators—such as intrinsic water-use efficiency, minimum leaf conductance, substomatal CO₂ concentration, and mesophyll conductance—are analysed in the context of how stress-induced discrepancies in data often result from measurement artefacts rather than true physiological differences. To address these challenges, the paper outlines practical approaches to improving measurement accuracy, offering insights on standardising experimental conditions and minimising errors. By recognising these issues, gaps in current knowledge are identified, providing a comprehensive overview of the challenges in interpreting leaf gas exchange data under stress conditions and suggesting areas for further study.

Cotton is frequently exposed to high temperatures during the reproductive stage, which can negatively impact productivity. While previous research has shown that photosynthesis can decrease under heat stress, there is limited information on the effects of heat stress during the reproductive phase on crop variables such as radiation capture, use efficiency, and yield. This study aimed to: (i) assess the effect of heat stress on cumulative intercepted PAR radiation (IRcum), radiation use efficiency (RUE), harvest index (HI), and yield, and (ii) evaluate potential interactions between heat stress and source-sink relationships during the reproductive phase. Two field experiments were conducted, with heating treatments applied before and after flowering, and controls without temperature manipulation. In Experiment 1, two genotypes with contrasting growth cycles were compared, while Experiment 2 examined intact versus defoliated plants. Heat stress significantly reduced yield and HI, particularly during post-flowering. Source reduction (defoliation) further reduced yield, independent of temperature. Although IRcum was unaffected by treatments, RUE dropped sharply under heat stress in intact plants and was similarly low in defoliated plants under both control and heated conditions. These results suggest that heat stress, especially during post-flowering, exacerbates the effects on cotton productivity by reducing both total plant dry weight and HI. The study highlights that the relationship between RUE and yield strongly depends on the specific limiting factors, such as heat stress or source restrictions.

Nitrogen is crucial for plant development and crop production. Amaranthus cruentus, a C4 species, has been pointed out as a high-nutritious and stress resilient crop. Here we studied the effects of sufficient and low nitrogen supplementation on the photosynthetic efficiency and metabolic responses of A. cruentus. Photochemical parameters from dark-adapted and transient chlorophyll fluorescence measurements, antioxidant enzymes activity, and metabolomic analysis, were evaluated to depict the impact of nitrogen availability. Photochemical parameters showed a significant decrease compared to those from gas exchange. The antioxidant enzymes activity revealed variations among treatments, being important at low nitrogen availability. At the metabolic level, there is a significant accumulation of L-glutamine, aromatic amino acids and ascorbic acid in A. cruentus with sufficient nitrogen. At low nitrogen, the metabolic profile of A. cruentus suggests stabilization of membrane structure and efficient use of available nitrogen by accumulating L-glutamic acid. The differential accumulation of L-glutamine and L-glutamic acid reflects an adaptive strategy for maintaining nitrogen. Nitrogen-rich conditions, the plant stores excess nitrogen as L-glutamine, while in deficiency, it utilizes L-glutamic acid for essential metabolic functions. Overall, A. cruentus activates a coordinated metabolic strategy under LN to optimize nitrogen use. This includes effective ROS detoxification via both enzymatic and non-enzymatic antioxidants, structural reinforcement through membrane-stabilizing lipids, and efficient nitrogen storage and redistribution to meet metabolic demands during nitrogen limitation.

Global climate change presents significant challenges to viticulture, particularly regarding water availability and nutrient management. This study delves into the combined effects of vertical cordon (VC) and gobelet (G) training systems, alongside deficit irrigation (DI) and rainfed (R) regimes, on the physiology, nutrient dynamics, and productivity of Vitis vinifera L. cv. Maturana Blanca. The research uncovers that VC training increases vegetative growth and yield through enhanced light exposure and bud load, but careful nutrient management is required to address reduced phosphorus, iron, and zinc levels. DI effectively mitigates water stress, enhances intrinsic and instantaneous water use efficiency, and impacts nutrient uptake, notably increasing calcium and manganese levels while reducing nitrogen. Leaf blade and petiole analyses demonstrated complementary roles in understanding nutrient transport and physiological responses, with petioles reflecting short-term changes and leaf blades capturing long-term trends. The findings underscore the potential of combining VC training and DI to optimize vineyard resilience and productivity under climate stress while maintaining a balanced vegetative and reproductive growth ratio essential for high-quality grape production.

The stratification of cold air is a phenomenon that typically occurs under certain topographic (closed ground depressions) and atmospheric conditions (stability and nocturnal radiative cooling). Under such conditions the drainage of the heavier cold air from the higher elevations causes its accumulation for days or weeks in the bottom of these depressions, leading temperatures to dramatically decrease and to decouple from regional climatic conditions. These particular locations which are frequent in karstic, volcanic and glacial landscapes, have been proposed to act as microrefugia of biodiversity in the context of climate warming. The existence of these cold air pools (CAPs) has been reported worldwide, and their biotic communities differ from equivalent sites out of these locations. However, there is an almost complete absence of ecophysiological studies concerning plant communities inhabiting CAPs. Thus, one of the objectives of this review is to hypothesize the effects of these specific conditions on the biology of the soil and the manner in which these plants should respond to such particular environmental conditions. Furthermore, given that temperature can decrease dramatically over short distances inside CAPs, in the present review we also propose their use as natural freezers for the study of plant responses to low temperatures.

Background: Among the consequences of global climate change, one of the most significant yet understudied is the increased frequency and intensity of heat waves. This article evaluates the responses to combined heat wave and drought in several crops and a non-crop species using an improved methodology to control temperature using IR lamps. Results: The effectiveness and precision of simulated heat waves with the system presented were verified at the experimental field of the University of the Balearic Islands. Using IR lamps, an artificial leaf was used to precisely control environmental temperature, a key aspect in simulating heat wave conditions. Concerning plant physiology, the effects of combined heat wave and drought on leaf relative water content (RWC) and photosynthetic parameters presented different patterns between species. Two remarkable particularities were (1) the observation that photosynthesis was sustained under RWC values well below those previously reported to cause complete photosynthesis cessation in C3 species and (2) the photosynthetic linear electron transport rate (ETR) was stimulated after retrieval of drought and heat wave far above their own initial values and those for control plants, also in some species. Conclusions: The use of an artificial leaf as major temperature sensor is key to provide highly realistic simulated heat waves. Using this technical setup, it was possible to determine that there is a large variability among species and some particularly intriguing observations strongly support the view that systematic experiments should be developed on different species and conditions to grab a significant knowledge on how will heat waves affect crop and vegetation in the near future.

The consequences of climate change on the ecophysiology of cryptogams, generally, and in ferns, particularly, are understudied. Phenomena induced by climate change, such as increased frequency of extreme weather events, shifts in precipitation patterns and temperature fluctuations, can significantly impact the physiology and distribution of ferns. The clade of ferns evolved about 400 million years ago and represents the sister group of seed plants. Given their long evolutionary history, ferns offer insights into the resilience and adaptability of plant lineages over geological time scales. Both from an evolutionary and functional perspective, ferns represent a crucial group with intermediate physiological properties between earlier-evolving bryophytes and spermatophytes. Additionally, their life cycle with single-celled reproductive spores and with two independent generations, gametophyte and sporophyte, which have strong anatomical and physiological differences and even different ecological requirements, make ferns a unique case study. While most ferns avoid freezing by living in the tropics or shedding their fronds, wintergreen species deal with subzero temperatures in temperate and cold ecosystems. Additionally, the chlorophyll-containing spores and/or gametophytes of many species also face subzero temperatures. Despite all this, our current knowledge of low temperature- and freezing-tolerance mechanisms in ferns is minimal. In this review we make a comprehensive compilation and re-evaluation of the available knowledge in this topic with a focus on photosynthetic cells/organs of ferns (class Polypodiopsida). We include some recent and relevant findings, identify major gaps and provide baseline for future lines of research.