ABA induces H₂O₂production in guard cells, but does not close the stomata onVicia fabaleaves developed at high air humidity

Abstract

Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure.

Role of guard-cell ABA in determining maximal stomatal aperture and prompt vapor-pressure-deficit response

“…6F). This is in agreement with previous studies that have shown that VPD conditions (1 to 4 days of exposure) affect stomatal aperture (Fanourakis et al , 2011; Aliniaeifard et al , 2014; Carvalho et al , 2015), the quantity of leaf ABA (Rezaei Nejad and van Meeteren, 2008; Arve et al , 2013; Giday et al , 2014) and stomatal sensitivity to ABA (Rezaei Nejad and van Meeteren, 2008; Aliniaeifard and Van Meeteren, 2013; Pantin et al , 2013 b ; Arve et al , 2014; Giday et al , 2014), which is reversed by the application of ABA (Fanourakis et al , 2011; Aliniaeifard et al , 2014) or air movement (Carvalho et al , 2015) during the low-VPD period. Growing GCabi plants under constant low-VPD conditions did not increase their leaf area, despite the observed increase in their RWC (Fig.…”

Stomatal VPD Response: There Is More to the Story Than ABA

“…It has been shown that stomatal responsiveness may be conditional on growth conditions (e.g. plants grown under very high humidity show reduced stomatal responsiveness to ABA; Pospíšilová, 1996;Pantin et al, 2013b;Arve et al, 2014). However, different growth conditions seem to be insufficient to explain the abovementioned differences between our results and those of McAdam et al ( , 2016b, even though different humidity regimes were used in our experiments.…”

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

“…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).…”