Stomatal malfunctioning under low VPD conditions: induced by alterations in stomatal morphology and leaf anatomy or in the ABA signaling?

Abstract

Exposing plants to low VPD reduces leaf capacity to maintain adequate water status thereafter. To find the impact of VPD on functioning of stomata, stomatal morphology and leaf anatomy, fava bean plants were grown at low (L, 0.23 kPa) or moderate (M, 1.17 kPa) VPDs and some plants that developed their leaves at moderate VPD were then transferred for 4 days to low VPD (M→L). Part of the M→L-plants were sprayed with ABA (abscisic acid) during exposure to L. L-plants showed bigger stomata, larger pore area, thinner leaves and less spongy cells compared with M-plants. Stomatal morphology (except aperture) and leaf anatomy of the M→L-plants were almost similar to the M-plants, while their transpiration rate and stomatal conductance were identical to that of L-plants. The stomatal response to ABA was lost in L-plants, but also after 1-day exposure of M-plants to low VPD. The level of foliar ABA sharply decreased within 1-day exposure to L, while the level of ABA-GE (ABA-glucose ester) was not affected. Spraying ABA during the exposure to L prevented loss of stomatal closing response thereafter. The effect of low VPD was largely depending on exposure time: the stomatal responsiveness to ABA was lost after 1-day exposure to low VPD, while the responsiveness to desiccation was gradually lost during 4-day exposure to low VPD. Leaf anatomical and stomatal morphological alterations due to low VPD were not the main cause of loss of stomatal closure response to closing stimuli.

The Evolution of Mechanisms Driving the Stomatal Response to Vapor Pressure Deficit

“…Interestingly, while we show here that foliar ABA appears to drive stomatal responses to changes in VPD in angiosperms, a number of studies have shown that the exposure of angiosperm leaves to low humidity is a critical prerequisite for delivering normal stomatal responses to ABA and that high humidity can desensitize stomata to ABA (Arve et al, 2013;Pantin et al, 2013b;Aliniaeifard et al, 2014). This interaction is more likely due to low humidity being a strong upregulator of both ABA synthetic and signaling genes (Pantin et al, 2013b) than being due to changes in stomatal or leaf anatomy at high humidity (Aliniaeifard et al, 2014).…”

“…This interaction is more likely due to low humidity being a strong upregulator of both ABA synthetic and signaling genes (Pantin et al, 2013b) than being due to changes in stomatal or leaf anatomy at high humidity (Aliniaeifard et al, 2014).…”

Fern Stomatal Responses to ABA and CO2 Depend on Species and Growth Conditions

“…1B and 2, A and B; Students t test, P , 0.05). This seems counterintuitive, as previous studies have shown higher stomatal conductance or wider stomatal aperture at higher RH in several angiosperm species (Torre et al, 2003;Nejad and van Meeteren, 2005;Fanourakis et al, 2011;Aliniaeifard et al, 2014). However, here, the measurements of stomatal behavior were carried out at ;70% RH, which was higher than the growth room RH of ;40%.…”

“…Air humidity has been shown to affect stomatal morphology and responsiveness in various angiosperm species. High relative air humidity during growth has been associated with longer and more open stomata (Torre et al, 2003;Nejad and van Meeteren, 2005;Fanourakis et al, 2011;Aliniaeifard et al, 2014), lower levels of ABA (Zeevaart, 1974;Nejad and van Meeteren, 2007;Okamoto et al, 2009;Aliniaeifard et al, 2014), and decreased stomatal responsiveness to ABA (Pospíšilová, 1996;Fanourakis et al, 2013;Pantin et al, 2013b;Arve et al, 2014). Exposure to low RH can enhance stomatal ABA responsiveness in young leaves that are constantly in a microenvironment with high RH (Pantin et al, 2013b).…”

Combining carbon-13 and oxygen-18 to unravel triticale grain yield and physiological response to water stress

“…According to Davies and Gowing (1999), plants are very sen- sitive to small differences in soil moisture and they respond to these moisture fluctuations by regulating their stomatal conductance, which in turn may affect the Ci/Ca ratio, which is a major determinant for 13 C discrimination in leaves. When moisture is freely available in the soil as under WW, more water is absorbed by the guard cells, which expand, opening the stomata thus allowing CO 2 to diffuse into the leaf (Aliniaeifard et al, 2014). Increased gs at a constant A increases the Ci/Ca ratio consequently allowing for more discrimination of 13 C by the CO 2 fixing enzyme Ribulose bisphosphate carboxylase-oxygenase (Rubisco) and the reverse is true.…”