Cytokinins: Moderators of Stomatal Movement in Poplar Genotypes

摘要

The role of exogenous ABA and cytokinins in stomatal control were examined in 1-year-old cuttings of three poplar genotypes; Popuulus x euramericana cv. I-214 (Italica). P. berolinemis (Berolinensis) and P. popularis 35-44 (Populans). ABA readily induced stomatal closure although stomatal sensitivity significantly differed among different genotypes. Its strong inhibitory effect could be distinctly overcome by cytokinins which were supplied either separately, or together with ABA via the transpirationstream. Furthermore, exogenous application of zeatin delayed the process of drought-induced stomatal closure. Since endogenous ABA increases whereas cytokinins are known to decrease during the onset of water stress, the concept of a compound root-drivensignal of soil drying was put forward and it is supposed that ABA/cytokinms regulate stomatal movements in root-shoot communications. In addition, the interactions between ABA and different forms of cytokinins including zeatin, kinetin and 6-benzyladenine (BA) were also investigated. Results showed that BA. an artificial cytokinin enhanced the inhibitory effect of ABA rather than overcoming its influence in contrast with zeatin and kinetin.