Stomatal closure is induced by hydraulic signals and maintained by ABA in drought-stressed grapevine

Abstract

Water saving under drought stress is assured by stomatal closure driven by active (ABA-mediated) and/or passive (hydraulic-mediated) mechanisms. There is currently no comprehensive model nor any general consensus about the actual contribution and relative importance of each of the above factors in modulating stomatal closure in planta. In the present study, we assessed the contribution of passive (hydraulic) vs active (ABA mediated) mechanisms of stomatal closure in V. vinifera plants facing drought stress. Leaf gas exchange decreased progressively to zero during drought, and embolism-induced loss of hydraulic conductance in petioles peaked to ~50% in correspondence with strong daily limitation of stomatal conductance. Foliar ABA significantly increased only after complete stomatal closure had already occurred. Rewatering plants after complete stomatal closure and after foliar ABA reached maximum values did not induced stomatal re-opening, despite embolism recovery and water potential rise. Our data suggest that in grapevine stomatal conductance is primarily regulated by passive hydraulic mechanisms. Foliar ABA apparently limits leaf gas exchange over long-term, also preventing recovery of stomatal aperture upon rewatering, suggesting the occurrence of a mechanism of long-term down-regulation of transpiration to favor embolism repair and preserve water under conditions of fluctuating water availability and repeated drought events.

Insights On the Impact of Arbuscular Mycorrhizal Symbiosis On Tomato Tolerance to Water Stress

“…On the contrary, in AM+ plants upon both NS and WS conditions, and in control plants upon NS conditions, no significant differences in endogenous ABA levels were detected, a result supported by the absence of transcriptional changes in the selected genes of the ABA core signaling pathway. In woody plants, such as grapevine, it has been demonstrated that stomatal closure can be driven both by active (ABA-mediated) and/or passive (hydraulicsmediated) mechanisms (Tombesi et al, 2015). Our results, showing that ABA concentrations remain low in AM+ plants, raise the question of whether an involvement of hydraulics-mediated mechanisms in the regulation of stomatal closing under WS could be proposed for mycorrhizal tomato too.…”

Water and forests in the Mediterranean hot climate zone: a review based on a hydraulic interpretation of tree functioning

“…Hydraulic and biochemical signals are involved in stomatal control (Tardieu et al, 2010;Torres-Ruiz et al, 2015). Yet, the integrated understanding of stomatal control is still poor (Brodribb & McAdam, 2011), and therefore modelling approaches remain fragmental (Damour et al, 2010;Tombesi et al, 2015). The hydraulic theory states that under water deficit (decrease in soil water potential or increase in atmospheric demand) stomata close to prevent the formation of xylem embolisms (Damour et al, 2010).…”

“…The hydraulic theory states that under water deficit (decrease in soil water potential or increase in atmospheric demand) stomata close to prevent the formation of xylem embolisms (Damour et al, 2010). Stomata can then be viewed as pressure regulators, buffering the drop of xylem water potential and the consequent risk of massive xylem embolism and catastrophic hydraulic failure (Tombesi et al, 2015). 4 sites in the Mediterranean region (e.g., Infante et al (1997) for Q. ilex near Seville, Spain).…”

Rice OsERF71-mediated root modification affects shoot drought tolerance

“…For example, drought treatment to roots causes leaf growth inhibition and stomatal behavior modification together with leaf cell-wall-hardening via osmotically generated hydraulic signals and ABA. 13,[23][24][25] Inhibition of leaf growth is often a primary plant response to moderate water stress. 23,26 However, since we found no developmental abnormality in shoots of OsERF71 overexpression rice plants, it is not persuasive.…”