Root-to-shoot ABA signaling does not contribute to genotypic variation in stomatal functioning induced by high relative air humidity

摘要

High relative air humidity (RH >= 85%) during leaf expansion hampers stomatal responsiveness to closing stimuli, a genotype-dependent effect. Genotypes with reduced stomatal closure in response to closing stimuli (i.e., sensitive genotypes) show low bulk leaf abscisic acid concentration ([ABA]). We hypothesized that the amount of ABA produced in the roots and delivered with the transpiration stream to the leaves is a critical step for a proper stomatal functioning in high RH-grown plants. Ten genotypes from a cut rose tetraploid population were grown at moderate (62%) or high (89%) RH. Stomatal anatomy and responsiveness to desiccation or ABA feeding were evaluated. Root and leaf petiole xylem sap [ABA] were quantified, and ABA delivery rate from root-to-shoot was estimated. High RH reduced stomatal responsiveness to both closing stimuli in the sensitive genotypes, whereas it had a nonsignificant effect in the tolerant ones. Estimates of [ABA] in root xylem sap at transpirational flow rate were not related to the genotypic differences in the sensitivity to high RH. However, high RH increased this concentration irrespective of the genotype, probably due to a reduced dilution of the [ABA] in the xylem sap as a result of a lower transpiration rate compared to moderate RH-grown plants. Leaf petiole xylem sap [ABA] was neither related to the genotypic differences in the sensitivity to high RH nor it was affected by RH. We concluded that genotypic differences in the stomatal sensitivity to high RH cannot be explained by changes in the [ABA] delivered with the transpiration stream from the roots to the leaves. (C) 2015 Elsevier B.V. All rights reserved.