Anther dehiscence is the process that facilitates pollen release from mature anthers in flowering plants. Despite its crucial importance to reproduction, the underlying developmental mechanism and its integration with environmental cues remain poorly understood. Establishing noninvasive, controlled humidity treatments of Arabidopsis thaliana flowers, we show here that high humidity prevents anthers from opening. Manipulation of stomatal densities alters dehiscence dynamics, suggesting a contribution of controlled transpiration. Furthermore, analyses of subcellular markers revealed the occurrence of a developmentally prepared and environmentally triggered programmed cell death (PCD) process in specific anther tissues, epidermis and endothecium. Notably, genetic inhibition of PCD delays anther dehiscence, whereas precocious PCD induction promotes it. Our data reveal a rapid PCD execution process modulated by ambient humidity as instrumental for timely pollen release in the flowering plant Arabidopsis.

• Klíčová slova
• anther dehiscence, humidity, pollen, programmed cell death, stomata,
• MeSH
• apoptóza * fyziologie   MeSH
• Arabidopsis * fyziologie   genetika   cytologie   MeSH
• květy * fyziologie   MeSH
• proteiny huseníčku metabolismus   genetika   MeSH
• průduchy rostlin fyziologie   MeSH
• pyl * fyziologie   MeSH
• regulace genové exprese u rostlin MeSH
• vlhkost * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• proteiny huseníčku MeSH

BACKGROUND AND AIMS: The benefits and costs of amphistomy (AS) vs. hypostomy (HS) are not fully understood. Here, we quantify benefits of access of CO2 through stomata on the upper (adaxial) leaf surface, using 13C abundance in the adaxial and abaxial epicuticular wax. Additionally, a relationship between the distribution of stomata and epicuticular wax on the opposite leaf sides is studied. METHODS: We suggest that the 13C content of long-chain aliphatic compounds of cuticular wax records the leaf internal CO2 concentration in chloroplasts adjacent to the adaxial and abaxial epidermes. This unique property stems from: (1) wax synthesis being located exclusively in epidermal cells; and (2) ongoing wax renewal over the whole leaf lifespan. Compound-specific and bulk wax 13C abundance (δ) was related to amphistomy level (ASL; as a fraction of adaxial in all stomata) of four AS and five HS species grown under various levels of irradiance. The isotopic polarity of epicuticular wax, i.e. the difference in abaxial and adaxial δ (δab - δad), was used to calculate the leaf dorsiventral CO2 gradient. Leaf-side-specific epicuticular wax deposition (amphiwaxy level) was estimated and related to ASL. KEY RESULTS: In HS species, the CO2 concentration in the adaxial epidermis was lower than in the abaxial one, independently of light conditions. In AS leaves grown in high-light and low-light conditions, the isotopic polarity and CO2 gradient varied in parallel with ASL. The AS leaves grown in high-light conditions increased ASL compared with low light, and δab - δad approached near-zero values. Changes in ASL occurred concomitantly with changes in amphiwaxy level. CONCLUSIONS: Leaf wax isotopic polarity is a newly identified leaf trait, distinguishing between hypo- and amphistomatous species and indicating that increased ASL in sun-exposed AS leaves reduces the CO2 gradient across the leaf mesophyll. Stomata and epicuticular wax deposition follow similar leaf-side patterning.

• Klíčová slova
• Brassica oleracea, Capsicum annuum, Amphistomy, abaxial, adaxial, carbon isotope, cuticle, epicuticular wax, leaf internal CO2 concentration, light, photosynthesis, stomata,
• MeSH
• epidermis rostlin * metabolismus   MeSH
• fotosyntéza MeSH
• izotopy uhlíku * analýza   MeSH
• listy rostlin * metabolismus   MeSH
• oxid uhličitý * metabolismus   MeSH
• průduchy rostlin * fyziologie   MeSH
• vosky * metabolismus   chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Carbon-13 MeSH Prohlížeč
• izotopy uhlíku * MeSH
• oxid uhličitý * MeSH
• vosky * MeSH

PREMISE: Increases in genome size in plants-often associated with larger, low-density stomata and greater water-use efficiency (WUE)-could affect plant ecophysiological and hydraulic function. Variation in plant genome size is often due to polyploidy, having occurred repeatedly in the austral sedge genus Schoenus in the Cape Floristic Region (CFR), while species in the other major schoenoid genus in the region, Tetraria, have smaller genomes. Comparing these genera is useful as they co-occur at the landscape level, under broadly similar bioclimatic conditions. We hypothesized that CFR Schoenus have greater WUE, with lower maximum stomatal conductance (gwmax) imposed by larger, less-dense stomata. METHODS: We investigated relationships between genome size and stomatal parameters in a phylogenetic context, reconstructing a phylogeny of CFR-occurring Schoeneae (Cyperaceae). Species' stomatal and functional traits were measured from field-collected and herbarium specimens. Carbon stable isotopes were used as an index of WUE. Genome size was derived from flow-cytometric measurements of leafy shoots. RESULTS: Evolutionary regressions demonstrated that stomatal size and density covary with genome size, positively and negatively, respectively, with genome size explaining 72-75% of the variation in stomatal size. Larger-genomed species had lower gwmax and C:N ratios, particularly in culms. CONCLUSIONS: We interpret differences in vegetative physiology between the genera as evidence of more-conservative strategies in CFR Schoenus compared to the more-acquisitive Tetraria. Because Schoenus have smaller, reduced leaves, they likely rely more on culm photosynthesis than Tetraria. Across the CFR Schoeneae, ecophysiology correlates with genome size, but confounding sources of trait variation limit inferences about causal relationships between traits.

• Klíčová slova
• Cape Floristic Region, Cyperaceae, functional traits, fynbos, genome size, polyploidy, stomatal size, water‐use efficiency,
• MeSH
• délka genomu * MeSH
• fylogeneze * MeSH
• genom rostlinný * MeSH
• listy rostlin fyziologie   genetika   anatomie a histologie   MeSH
• průduchy rostlin * fyziologie   genetika   MeSH
• šáchorovité genetika   fyziologie   MeSH
• voda fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• voda MeSH

Stomata play a pivotal role in regulating gas exchange between plants and the atmosphere controlling water and carbon cycles. Accordingly, we investigated the impact of ultraviolet-B radiation, a neglected environmental factor varying with ongoing global change, on stomatal morphology and function by a Comprehensive Meta-Analysis. The overall UV effect at the leaf level is to decrease stomatal conductance, stomatal aperture and stomatal size, although stomatal density was increased. The significant decline in stomatal conductance is marked (6% in trees and >10% in grasses and herbs) in short-term experiments, with more modest decreases noted in long-term UV studies. Short-term experiments in growth chambers are not representative of long-term field UV effects on stomatal conductance. Important consequences of altered stomatal function are hypothesized. In the short term, UV-mediated stomatal closure may reduce carbon uptake but also water loss through transpiration, thereby alleviating deleterious effects of drought. However, in the long term, complex changes in stomatal aperture, size, and density may reduce the carbon sequestration capacity of plants and increase vegetation and land surface temperatures, potentially exacerbating negative effects of drought and/or heatwaves. Therefore, the expected future strength of carbon sink capacity in high-UV regions is likely overestimated.

• Klíčová slova
• UV‐B, carbon sink, plant stress responses, review, stomatal aperture, stomatal conductance and transpiration, stomatal size and density,
• MeSH
• ekosystém MeSH
• listy rostlin fyziologie   MeSH
• průduchy rostlin * fyziologie   MeSH
• rostliny MeSH
• transpirace rostlin fyziologie   MeSH
• ultrafialové záření * MeSH
• voda fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• metaanalýza MeSH
• Názvy látek
• voda MeSH

Co-occurring heat and drought stresses challenge crop performance. Stomata open to promote evaporative cooling during heat stress, but close to retain water during drought stress, which resulted in complex stomatal regulation under combined heat and drought. We aimed to investigate stomatal regulation in leaves and flowers of perennial, indeterminate cultivars of tomatoes subjected to individual and combined heat and drought stress followed by a recovery period, measuring morphological, physiological, and biochemical factors involved in stomatal regulation. Under stress, stomata of leaves were predominantly affected by drought, with lower stomatal density and stomatal closing, resulting in significantly decreased photosynthesis and higher leaf temperature. Conversely, stomata in sepals seemed affected mainly by heat during stress. The differential patterns in stomatal regulation in leaves and flowers persisted into the recovery phase as contrasting patterns in stomatal density. We show that flower transpiration is regulated by temperature, but leaf transpiration is regulated by soil water availability during stress. Organ-specific patterns of stomatal development and abscisic acid metabolism mediated this phenomenon. Our results throw light on the dual role of stomata in heat and drought tolerance of vegetative and generative organs, and demonstrate the importance of considering flower surfaces in the phenotyping of stomatal reactions to stress.

• Klíčová slova
• ABA, combined stress, drought, flower, heat, perennials, photosynthesis, recovery, stomata, tomato,
• MeSH
• květy metabolismus   MeSH
• kyselina abscisová metabolismus   MeSH
• listy rostlin metabolismus   MeSH
• období sucha MeSH
• průduchy rostlin fyziologie   MeSH
• Solanum lycopersicum * MeSH
• voda metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyselina abscisová MeSH
• voda MeSH

The regulation of water loss and the spread of xylem embolism have mostly been considered separately. The development of an integrated approach taking into account the temporal dynamics and relative contributions of these mechanisms to plant drought responses is urgently needed. Do conifer species native to mesic and xeric environments display different hydraulic strategies and temporal sequences under drought? A dry-down experiment was performed on seedlings of four conifer species differing in embolism resistance, from drought-sensitive to extremely drought-resistant species. A set of traits related to drought survival was measured, including turgor loss point, stomatal closure, minimum leaf conductance, and xylem embolism resistance. All species reached full stomatal closure before the onset of embolism, with all but the most drought-sensitive species presenting large stomatal safety margins, demonstrating that highly drought-resistant species do not keep their stomata open under drought conditions. Plant dry-down time to death was significantly influenced by the xylem embolism threshold, stomatal safety margin, and minimum leaf conductance, and was best explained by the newly introduced stomatal margin retention index (SMRIΨ50) which reflects the time required to cross the stomatal safety margin. The SMRIΨ50 may become a key tool for the characterization of interspecific drought survival variability in trees.

• Klíčová slova
• Drought tolerance, embolism resistance, residual transpiration, stomatal closure, stomatal safety margin, tree mortality,
• MeSH
• cévnaté rostliny * MeSH
• embolie * MeSH
• listy rostlin fyziologie   MeSH
• období sucha MeSH
• průduchy rostlin fyziologie   MeSH
• stromy fyziologie   MeSH
• transpirace rostlin fyziologie   MeSH
• voda fyziologie   MeSH
• xylém fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• voda MeSH

Polyploidy plays an important role in plant evolution, but knowledge of its eco-physiological consequences, such as of the putatively enlarged stomata of polyploid plants, remains limited. Enlarged stomata should disadvantage polyploids at low CO2 concentrations (namely during the Quaternary glacial periods) because larger stomata are viewed as less effective at CO2 uptake. We observed the growth, physiology, and epidermal cell features of 15 diploids and their polyploid relatives cultivated under glacial, present-day, and potential future atmospheric CO2 concentrations (200, 400, and 800 ppm respectively). We demonstrated some well-known polyploidy effects, such as faster growth and larger leaves, seeds, stomata, and other epidermal cells. The stomata of polyploids, however, tended to be more elongated than those of diploids, and contrary to common belief, they had no negative effect on the CO2 uptake capacity of polyploids. Moreover, polyploids grew comparatively better than diploids even at low, glacial CO2 concentrations. Higher polyploids with large genomes also showed increased operational stomatal conductance and consequently, a lower water-use efficiency. Our results point to a possible decrease in growth superiority of polyploids over diploids in a current and future high CO2 climatic scenarios, as well as the possible water and/or nutrient dependency of higher polyploids.

• Klíčová slova
• atmospheric carbon dioxide, cell size, climate change, genome size, glacial periods, photosynthesis, polyploidy, stomatal conductance,
• MeSH
• fotosyntéza * fyziologie   MeSH
• listy rostlin fyziologie   MeSH
• oxid uhličitý farmakologie   MeSH
• průduchy rostlin * fyziologie   MeSH
• voda MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• oxid uhličitý MeSH
• voda MeSH

Arabidopsis thaliana SYNAPTOTAGMIN 1 (AtSYT1) was shown to be involved in responses to different environmental and biotic stresses. We investigated gas exchange and chlorophyll a fluorescence in Arabidopsis wild-type (WT, ecotype Col-0) and atsyt1 mutant plants irrigated for 48 h with 150 mM NaCl. We found that salt stress significantly decreases net photosynthetic assimilation, effective photochemical quantum yield of photosystem II (ΦPSII), stomatal conductance and transpiration rate in both genotypes. Salt stress has a more severe impact on atsyt1 plants with increasing effect at higher illumination. Dark respiration, photochemical quenching (qP), non-photochemical quenching and ΦPSII measured at 750 µmol m-2 s-1 photosynthetic photon flux density were significantly affected by salt in both genotypes. However, differences between mutant and WT plants were recorded only for qP and ΦPSII. Decreased photosynthetic efficiency in atsyt1 under salt stress was accompanied by reduced chlorophyll and carotenoid and increased flavonol content in atsyt1 leaves. No differences in the abundance of key proteins participating in photosynthesis (except PsaC and PsbQ) and chlorophyll biosynthesis were found regardless of genotype or salt treatment. Microscopic analysis showed that irrigating plants with salt caused a partial closure of the stomata, and this effect was more pronounced in the mutant than in WT plants. The localization pattern of AtSYT1 was also altered by salt stress.

• Klíčová slova
• Arabidopsis thaliana, SYNAPTOTAGMIN 1, photosynthesis, salt stress, stomata,
• MeSH
• Arabidopsis fyziologie   účinky záření   MeSH
• biologické pigmenty metabolismus   MeSH
• chlorofyl a metabolismus   MeSH
• fluorescence MeSH
• fotosyntéza fyziologie   účinky záření   MeSH
• plyny metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• průduchy rostlin cytologie   fyziologie   účinky záření   MeSH
• solný stres fyziologie   účinky záření   MeSH
• světlo MeSH
• synaptotagmin I nedostatek   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biologické pigmenty MeSH
• chlorofyl a MeSH
• plyny MeSH
• proteiny huseníčku MeSH
• synaptotagmin I MeSH
• SYT1 protein, Arabidopsis MeSH Prohlížeč

Interactions between climate change and UV penetration in the biosphere are resulting in the exposure of plants to new combinations of UV radiation and drought. In theory, the impacts of combinations of UV and drought may be additive, synergistic or antagonistic. Lack of understanding of the impacts of combined treatments creates substantial uncertainties that hamper predictions of future ecological change. Here, we compiled information from 52 publications and analysed the relative impacts of UV and/or drought. Both UV and drought have substantial negative effects on biomass accumulation, plant height, photosynthesis, leaf area and stomatal conductance and transpiration, while increasing stress-associated symptoms such as MDA accumulation and reactive-oxygen-species content. Contents of proline, flavonoids, antioxidants and anthocyanins, associated with plant acclimation, are upregulated both under enhanced UV and drought. In plants exposed to both UV and drought, increases in plant defense responses are less-than-additive, and so are the damage and growth retardation. Less-than-additive effects were observed across field, glasshouse and growth-chamber studies, indicating similar physiological response mechanisms. Induction of a degree of cross-resistance seems the most likely interpretation of the observed less-than-additive responses. The data show that in future climates, the impacts of increases in drought exposure may be lessened by naturally high UV regimes.

• Klíčová slova
• additive effect, cross-resistance, stress, synergistic effect,
• MeSH
• aklimatizace * fyziologie   MeSH
• biomasa MeSH
• fotosyntéza MeSH
• fyziologie rostlin * účinky záření   MeSH
• listy rostlin fyziologie   MeSH
• období sucha * MeSH
• průduchy rostlin fyziologie   MeSH
• transpirace rostlin fyziologie   MeSH
• ultrafialové záření * MeSH
• Publikační typ
• časopisecké články MeSH
• metaanalýza MeSH
• práce podpořená grantem MeSH

Ozone (O3) is a gaseous environmental pollutant that can enter leaves through stomatal pores and cause damage to foliage. It can induce oxidative stress through the generation of reactive oxygen species (ROS) like hydrogen peroxide (H2O2) that can actively participate in stomatal closing or opening in plants. A number of phytohormones, including abscisic acid (ABA), ethylene (ET), salicylic acid (SA), and jasmonic acid (JA) are involved in stomatal regulation in plants. The effects of ozone on these phytohormones' ability to regulate the guard cells of stomata have been little studied, however, and the goal of this paper is to explore and understand the effects of ozone on stomatal regulation through guard cell signaling by phytohormones. In this review, we updated the existing knowledge by considering several physiological mechanisms related to stomatal regulation after response to ozone. The collected information should deepen our understanding of the molecular pathways associated with response to ozone stress, in particular, how it influences stomatal regulation, mitogen-activated protein kinase (MAPK) activity, and phytohormone signaling. After summarizing the findings and noting the gaps in the literature, we present some ideas for future research on ozone stress in plants.

• Klíčová slova
• abscisic acid, ethylene, guard cells, hydrogen peroxide (H2O2), reactive oxygen species (ROS), salicylic acid,
• MeSH
• biologické modely MeSH
• mitogenem aktivované proteinkinasy metabolismus   MeSH
• ozon farmakologie   MeSH
• průduchy rostlin účinky léků   fyziologie   MeSH
• regulátory růstu rostlin farmakologie   MeSH
• signální transdukce účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• mitogenem aktivované proteinkinasy MeSH
• ozon MeSH
• regulátory růstu rostlin MeSH