High relative air humidity and continuous light reduce stomata functionality by affecting the ABA regulation in rose leaves

Abstract

Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and b-glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and b-glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA-glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low b-glucosidase activity converting ABA-GE to ABA. Continuous lighting (24 h) resulted in low levels of b-glucosidase activity irrespective of RH, indicating that a dark period is essential to activate b-glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that b-glucosidase is a key enzyme regulating the ABA pool in rose plants.

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).…”

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

“…The reasons for altered stomatal morphology are not yet understood. Recent studies have suggested that stomatal malfunctioning in low RH-grown leaves is a consequence of a high foliar abscisic acid content during leaf development at decreased atmospheric humidity, compared with leaves grown in a more humid atmosphere [21,74]. However, it has been shown that shorter stomata have faster response times than larger ones [24].…”

Developmental Priming of Stomatal Sensitivity to Abscisic Acid by Leaf Microclimate

“…Conversely, high RH induces ABA catabolism and stomatal opening [24]. Interestingly, plants grown under high RH show a weak stomatal response to ABA [25,26]. We therefore hypothesized that high RH around young leaves could be the primary environmental signal maintaining stomatal insensitivity to ABA, whereas older leaves are sensitized to ABA by being exposed to lower ambient RH.…”