Foliar abscisic acid content underlies genotypic variation in stomatal responsiveness after growth at high relative air humidity

Abstract

Background and Aims Stomata formed at high relative air humidity (RH) respond less to abscisic acid (ABA), an effect that varies widely between cultivars. This study tested the hypotheses that this genotypic variation in stomatal responsiveness originates from differential impairment in intermediates of the ABA signalling pathway during closure and differences in leaf ABA concentration during growth. Methods Stomatal anatomical features and stomatal responsiveness to desiccation, feeding with ABA, three transduction elements of its signalling pathway (H2O2, NO, Ca2+) and elicitors of these elementswere determined in four rose cultivars grown at moderate (60 %) and high (90 %) RH. Leaf ABA concentration was assessed throughout the photoperiod and following mild desiccation (10 % leaf weight loss). Key Results Stomatal responsiveness to desiccation andABAfeedingwas little affected by highRHin two cultivars, whereas it was considerably attenuated in two other cultivars (thus termed sensitive). Leaf ABA concentration was lower in plants grown at high RH, an effect thatwas more pronounced in the sensitive cultivars. Mild desiccation triggered an increase in leafABAconcentration and equalized differences between leaves grownatmoderate and highRH. High RH impaired stomatal responses to all transduction elements, but cultivar differences were not observed. Conclusions HighRHresulted in decreased leafABAconcentration during growth as a result of lack ofwater deficit, since desiccation induced ABA accumulation. Sensitive cultivars underwent a larger decrease in leaf ABA concentration rather than having a higherABAconcentration threshold for inducing stomatal functioning.However, cultivar differences in stomatal closure followingABA feeding were not apparent in response toH2O2 and downstreamelements, indicating that signalling events prior to H 2O2 generation are involved in the observed genotypic variation. © The Author 2013.