Smaller stomata require less severe leaf drying to close: A case study in Rosa hydrida

Jatropha curcas L. (Euphorbiaceae) modulates stomatal traits in response to leaf-to-air vapor pressure deficit

“…They could, therefore, open at sunrise and close more quickly, allowing CO 2 fixation at times of the day that are associated with low transpiration rates (low VPD), resulting in higher WUE i [22,24,75]. We have shown that the strong correlations support the idea that high plasticity in SD would be closely associated with P N and WUE i in J. curcas leaves [1,13]; smaller stomata require less severe leaf drying to close [17], contributing to increased WUE i . Thus, water-limited environments are expected have species with the greatest WUE i [1,13].…”

“…Consequently, the effect of environmental features on leaf conductance involves both long-term processes and short-term dynamics. Short-term events are mediated by adjustments in pore aperture and are reversible, while long-term processes refer to leaf expansion and involve stomatal size and density [17,18]. Aasamaa and Sõber [19] compared the effects of different environmental conditions and found that the stomata of six temperate deciduous tree species grown in a greenhouse responded more strongly to changes in hydraulic environmental factors, e.g., air humidity and water supply than to changes in photosynthetic environmental factors, e.g., light intensity and air CO 2 concentration.…”

“…However, at the leaf level, g s is not solely determined by stomatal pore aperture but also depends on stomatal density (SD), pore length and pore depth [21]. Variation in stomatal size will therefore largely determine optimization of water flux under water-limiting conditions [17].…”

Growth in continuous high air humidity increases the expression of CYP707A-genes and inhibits stomatal closure

“…We also found that the size of the stomata was larger in WT and aba3-1 mutants developed in high RH and in aba3-1 mutants from moderate RH, compared with WT plants grown in moderate RH, showing a correlation between stomatal size and ABA content. An earlier study on Populus x canescens also found that ABA insensitive plants had larger stomata (Arend et al, 2009) and a study on Rosa x hybrida has shown that smaller stomata required less water loss to close (Giday et al, 2013b). This indicates that lack of ABA, reduced sensitivity to ABA or low ABA contents results in the development of large stomata.…”

Developmental Priming of Stomatal Sensitivity to Abscisic Acid by Leaf Microclimate

“…Insensitivity to ABA in young leaves is unexpected, especially as stomata of young leaves are smaller than in fully expanded leaves ( Figure 1D), while across species, stomatal movements in response to various stimuli are faster in small stomata [21,22]. Because stomata of young leaves are also rounder and probably less mechanically operational than in fully expanded leaves ( Figure 1D), elongation and maturation of guard cells could facilitate the developmental acquisition of stomatal responsiveness to ABA.…”