PLANT STOMATA ENCYCLOPEDIA

Zhaoguo Wang, 
Martijn Slot, 
Chuankuan Wang (2026)

Nat Commun – https://doi.org/10.1038/s41467-025-68250-x –

https://www.nature.com/articles/s41467-025-68250-x#citeas –

Abstract

Elevated temperatures pose challenges to stomatal conductance, which regulates transpiration and photosynthesis. However, the coupling of stomatal conductance, transpiration and photosynthesis may shift with warming.

Here, we synthesize evidence from a meta-analysis of 207 studies to assess leaf physiological responses to warming. On average, the responses of stomatal conductance are highly variable, exhibiting no consistent directional trend, whereas transpiration increases and photosynthesis decreases, reflecting a shift towards transpirational cooling. Stomatal conductance declines until temperatures exceed 5 °C above ambient, whereas transpiration remains stable under warming <3 °C. Beyond these two thresholds, both stomatal conductance and transpiration increase with further warming. The sensitivity of stomatal conductance, photosynthesis, and water-use efficiency to warming varies substantially among plant functional types, with distinct responses across life forms, phylogenetic groups, and photosynthetic pathways. Higher mean annual temperature amplifies the positive responses of stomatal conductance and transpiration to warming, whereas greater mean annual precipitation mitigates the warming-induced declines in photosynthesis. Elevated CO₂ exacerbates warming-induced declines in photosynthesis, while drought constrains transpirational cooling.

Collectively, these findings highlight a progressive decoupling of stomatal conductance, transpiration and photosynthesis with warming, revealing complex trade-offs between plant water use, thermal regulation, and carbon assimilation.

Huihui Fang ¹, Wenjia Chen ¹, Kehong Xing ¹, Liai Xu ¹, Jianguo Wu ¹, Yunshuai Huang ¹, Yanxi Pei ², Yunxiang Zang ³ (2025)

• ¹ Key Laboratory of Quality and Safety Control for Subtropical Fruit and Vegetable, Ministry of Agriculture and Rural Affairs, Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang 311300, China.
• ² School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi 030006, China.
• ³ Key Laboratory of Quality and Safety Control for Subtropical Fruit and Vegetable, Ministry of Agriculture and Rural Affairs, Collaborative Innovation Center for Efficient and Green Production of Agriculture in Mountainous Areas of Zhejiang Province, College of Horticulture Science, Zhejiang A&F University, Hangzhou, Zhejiang 311300, China.

Abstract

Heat stress (HS) severely limits plant growth and crop yields, becoming a critical challenge for global food production. As a gasotransmitter, hydrogen sulfide (H₂S) has been reported to participate in plants HS adaptation, however, the underlying mechanism remains unclear. Time-course analysis showed that HS duration-dependently boosted endogenous H₂S production, with both transcriptional upregulation and enzymatic activation of the L-Cysteine desulfhydrase 1 (DES1). Over-expression of DES1 enhanced basal thermotolerance in Arabidopsis, whereas the DES1 knockout mutant (des1) exhibited heightened sensitivity to HS.

Additionally, HS triggered stomatal closure and elevated stomatal density were substantially attenuated in des1, but more pronounced in OE-DES1. Importantly, the heat-sensitive phenotype and defective HS-induced stomatal responses in des1 could be rescued by exogenous H₂S pretreatment. Under HS condition, H₂S generated by DES1 triggered stomatal closure by regulating the expression of K⁺_in channel encoding genes, at least KAT1 and KC1, thereby modulating K⁺ homeostasis and turgor pressure of guard cells.

Concurrently, DES1-H₂S up-regulated the expression of genes associated stomatal development, SPCH and TMM, increasing stomatal density. Correspondingly, des1 had decreased level of relative water content, chlorophyll levels, and RuBisCO activity during HS, while OE-DES1 had the opposite effects. Overall, H₂S might act as an equilibrator of stomatal aperture and stomatal density to avoid excessive transpiration and maximize gaseous exchange then photosynthetic efficiency of leaves under HS.

Our study elucidates how H₂S optimizes stomatal behavior to improve basal thermotolerance, providing new insights into H₂S signaling and potential applications in breeding heat-resistant crops.

Keywords: Heat stress; Hydrogen sulfide; L-Cysteine desulfhydrase 1; Stomatal closure; Stomatal density.

Denise Scuffi ¹, Rosario Pantaleno ¹, Paula Schiel ¹, Jan-Ole Niemeier ², Alex Costa ³, Markus Schwarzländer ², Ana M Laxalt ¹, Carlos García-Mata ¹

• ¹ Instituto de Investigaciones Biológicas, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Científicas y Técnicas (IIB-UNMdP-CONICET), Mar del Plata 7600, Argentina.
• ² Institute of Plant Biology and Biotechnology (IBBP), University of Münster, Schlossplatz 8, Münster 48143, Germany.
• ³ Department of Biosciences, University of Milan, Milan 20133, Italy.

Plant Physiol. 199(4): kiaf561 – doi: 10.1093/plphys/kiaf561 – PMID: 41432548 –

https://pubmed.ncbi.nlm.nih.gov/41432548/ –

Abstract

Stomata are natural pores through which plants exchange gases with the environment, mainly carbon dioxide and oxygen required for photosynthesis and respiration, as well as water vapor through evapotranspiration. However, they also serve as entry points for microbial pathogens such as Pseudomonas syringae pv. tomato (Pst) bacteria.

To prevent microbe invasion, guard cells detect pathogen-associated molecular patterns (PAMPs), including the bacterial peptide flagellin (flg22), triggering stomatal closure. This study identifies hydrogen sulfide (H2S) and its cytosolic source L-CYSTEINE DESULFHYDRASE 1 (DES1) as key players in stomatal immunity.

We demonstrate that H2S and DES1 are involved in flg22- and bacterial-induced responses, including stomatal closure and modulation of reactive oxygen species (ROS) production, in Arabidopsis (Arabidopsis thaliana). Knockout mutants defective in the DES1 gene exhibited reduced susceptibility to Pst spray-inoculation and lower apoplastic and cytosolic H2O2 levels in response to flg22. Additionally, H2S independently induced cytosolic H2O2 levels in guard cells without requiring RBOHD activity. These findings establish H2S and its source, DES1, as critical components of the stomatal immune response.

Lawren Sack 

PNAS 123 (1) e2530591122 – https://doi.org/10.1073/pnas.2530591122 –

https://www.pnas.org/doi/10.1073/pnas.2530591122 –

Christoph Leuschner, Florian Schipka, Katharina Backes (2022)

https://doi.org/10.1093/treephys/tpab104 –

https://academic.oup.com/treephys/article-abstract/42/2/365/6355061?redirectedFrom=fulltext&login=false –

Abstract

The iso/anisohydric continuum has been used to classify tree species’ drought response strategies. The range over which stomata are regulating leaf water potential (ψ_l) before turgor loss occurs can be described with metrics such as the dependence of ψ_l on soil water potential (ψ_soil) and the size of ‘hydroscape area’ (HA), but corresponding field data from adult trees are scarce.

We examined the stomatal conductance (g_s)–ψ_l relationship in its temporal (diurnal vs seasonal and interannual) and spatial (within-crown vs between-site) variation in European beech, using extensive ψ_l and g_s measurements in the canopy of four beech stands across a precipitation gradient, and complemented the data set by published ψ_l and g_s measurements in further Central European beech stands (including the extreme 2018 drought) in order to cover the full water potential operation space of the species. Both metrics characterize beech as a strictly anisohydric species with δψ_l/δψ_soil >> 1 and HA = 4 MPa².

However, stomates close sensitively in response to increasing vapor pressure deficit, disproving the widely assumed dependence of large ψ_l variation on looser stomatal control. Characterizing the water status regulation mechanisms of trees requires separating diurnal from day-to-day variation in ψ_l and g_s. The large diurnal and seasonal ψ_l variation in beech leaves is partly caused by a low leaf tissue elasticity, suggesting that a whole-plant perspective with consideration of osmotic and elastic tissue properties and stem and root hydraulics is needed for fully understanding ψ_l regulation and the drought tolerance strategy of trees.

Matthias Arend, Richard L. Peters, Cedric Zahnd, Mladen Ognjenovic, Günter Hoch, Ansgar Kahmen (2025)

Physiological Plant Ecology, Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland

Plant Ecology, Department of Environmental Sciences, University Trier, Behringstraße 21, Trier, 54296 Germany

New Phytologist-Early View – https://doi.org/10.1111/nph.70847 –

https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.70847 –

We critically assessed the iso-/anisohydry concept, which builds on the assumption of tight stomatal regulation of water potential during tree dehydration. We found a consistent pattern of early stomatal closure in mature trees of eight tested species that precedes the decline of water potential in advanced stages of tree dehydration. This calls for a revision of the iso-/anisohydry concept in which early stomatal closure prevents trees from entering an advanced stage of dehydration.

John N Ferguson ¹, Peter Schmuker ¹, Anna Dmitrieva ¹, Truyen Quach ², Tieling Zhang ², Zhengxiang Ge ², Natalya Nersesian ², Shirley J Sato ², Tom E Clemente ², Andrew D B Leakey ^1 3 4

• ¹ Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
• ² Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, USA.
• ³ Department of Plant Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
• ⁴ Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

J Exp Bot. 75(21): 6823-6836 – doi: 10.1093/jxb/erae289 – PMID: 39021331 – PMCID: PMC11565208 –

https://pubmed.ncbi.nlm.nih.gov/39021331/ –

Abstract

Enhancing crop water use efficiency (WUE) is a key target trait for climatic resilience and expanding cultivation on marginal lands. Engineering lower stomatal density to reduce stomatal conductance (gs) has improved WUE in multiple C3 crop species. However, reducing gs in C3 species often reduces photosynthetic carbon gain. A different response is expected in C4 plants because they possess specialized anatomy and biochemistry which concentrates CO2 at the site of fixation. This modifies the relationship of photosynthesis (AN) with intracellular CO2 concentration (ci), such that photosynthesis is CO2 saturated and reductions in gs are unlikely to limit AN.

To test this hypothesis, genetic strategies were investigated to reduce stomatal density in the C4 crop sorghum. Constitutive expression of a synthetic epidermal patterning factor (EPF) transgenic allele in sorghum led to reduced stomatal densities, reduced gs, reduced plant water use, and avoidance of stress during a period of water deprivation.

In addition, moderate reduction in stomatal density did not increase stomatal limitation to AN. However, these positive outcomes were associated with negative pleiotropic effects on reproductive development and photosynthetic capacity. Avoiding pleiotropy by targeting expression of the transgene to specific tissues could provide a pathway to improved agronomic outcomes.

Keywords: Sorghum bicolor; C4 photosynthesis; stomata; water-use efficiency.

Joseph D Crawford , Dustin Mayfield-Jones , Glenn A Fried , Nicolas Hernandez , Andrew D B Leakey (2025)

Plant Physiology 199(4): kiaf600 –  https://doi.org/10.1093/plphys/kiaf600 –

https://academic.oup.com/plphys/article/199/4/kiaf600/8325470 –

Abstract

Stomatal anatomy (aperture area, length, and width) influences leaf-level physiology traits including conductance to water vapor. Stomatal anatomy can be visualized in situ by microscopy, but the difficulty of regulating the atmospheric environment of a microscope stage means that the conditions under which imaging is done are rarely physiologically relevant. Alternatively, leaf gas exchange instruments that measure gas fluxes reflect stomatal anatomical characteristics in aggregate, but the relative strengths of anatomical traits to control water use (e.g. size vs density) cannot be firmly established.

To reconcile the microscopic stomatal characteristics with leaf-level gas exchange, we describe a tool that combines laser scanning confocal microscopy, gas exchange instruments, and machine-learning image analysis to simultaneously observe anatomical characteristics of many (>40) stomata alongside leaf-level traits like photosynthesis, transpiration, and stomatal conductance. We demonstrate how the tool has the resolution capable of quantifying aperture sizes and variability in maize (Zea mays) leaves under 5 steady-state light/pCO₂ treatments while tightly controlling other environmental variables like relative humidity and temperature.

A model used to calculate stomatal conductance from measured apertures and stomatal density accurately matched stomatal conductance measured by gas exchange. This technical advancement will provide insight on how stomatal anatomy and function trade off to influence stomatal conductance and leaf-level water use efficiency.

Sunday A. ADENIRAN1, Akeem B. KADIRI2, James D. OLOWOKUDEJO2,

1 University of Ilorin, Department Plant Biology, Ilorin Nigeria;

2 University of Lagos, Department Botany, Akoka Yaba Lagos, Nigeria;

Notulae Scientia Biologicae 12(3): 637-645 – DOI:10.15835/nsb12310686 –

https://www.researchgate.net/publication/362578729_Comparative_foliar_epidermal_morphology_of_Isolona_Engl_Annonaceae

Abstract

A qualitative micromorphological assessment of the seven species of Isolona occurring in Nigeria and the Cameroons was undertaken with the aid of light microscope. The stomatal cells are particularly useful, providing stable characters which can be reliably employed in distinguishing the species.

Hypostomatic leaves and paracytic stomatal type are generic constant. Possession of only paracytic stomata is characteristic of I. dewevrei whereas other species may have in addition another type such as 1+2 laterocytic stomatal type found only in I. zenkeri and presence of brachyparacytic stomata which shows relatedness of I. campanulata, I.congolana, I. hexaloba, I. pleurocarpus and I. thonneri.

The epidermal surfaces appeared glabrous but an indication of hairs is shown by the presence of a glandular trichome base only in I. hexaloba. The epidermal cell characters such as epidermal cell shapes and anticlinal wall patterns seem to intergrade and they are not as definite as the stomatal cells. However, a combination of these features will be helpful in defining the species better and their leaf fragments can be differentiated based on the various characters studied for effective utilization in herbal medicinal research

Nik Woning, Yazen Al-Salman, Elias Kaiser, Sarah R. Berman, Oliver Brendel, Francisco Javier Cano, Sebastien Carpentier, Mauro Centritto, Paul L. Drake, Maxime Durand, David Eyland, Peter J. Franks, Théo Gerardin, Oula Ghannoum, Matthew Haworth, Liisa Kübarsepp, Tracy Lawson, Didier Le Thiec, Yong Li, L.F.M. Marcelis, Giovanni Marino, Lorna McAusland, Christopher D. Muir, Ülo Niinemets, Tiago Nunes, Michael Raissig, Kazuma Sakoda, Daisuke Sugiura, Tiina Tosens, Qiangqiang Zhang, Ningyi Zhang, Silvère Vialet-Chabrand (2025)

New Phytologist – DOI: 10.1111/nph.70842 –

https://www.researchgate.net/publication/399136337_Revisiting_the_relationship_between_stomatal_size_and_speed_across_species_-_a_meta-analysis –

Abstract and figures

The rate of stomatal opening and closure in response to changes in light affects leaf photosynthesis and water use. However, it is unclear how strongly stomatal size (SS) and density (SD) influence stomatal conductance (gs) kinetics, and whether variation arises from methodological differences, guard cell type or degree of amphistomaty.

We divided published records combining stomatal kinetics and anatomical traits from 89 species into kidney and dumbbell‐shaped guard cells, and evaluated four dynamic gs models on them. We derived the time constant for an exponential response of gs (τ) and the maximum rate of change (Slmax) as well as the ratio of adaxial/abaxial SD (rSD).

We found significant differences in parameter estimation between models. Stomatal anatomical traits and kinetic parameters showed large variation across species. While individual anatomical features (SS, SD, rSD and guard cell types) were weakly correlated with stomatal response speed (τ and Slmax), interactions between these features showed significant effects, demonstrating that kinetic performance arises from synergistic rather than additive anatomical relationships.

Our results call for the use of our unified modeling approach, challenge the generality of the observation that smaller stomata move faster across species and suggest rSD as an understudied driver of stomatal kinetics.