Golan A, Tepper M, Soudry E, Horwitz B A, Gepstein S
Department of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
Plant Physiol. 1996 Nov;112(3):901-4. doi: 10.1104/pp.112.3.901.
Cytokinin replaces light in several aspects of the photomorphogenesis of dicot seedlings. Arabidopsis thaliana seedlings grown under red light have been shown to become disoriented, losing the negative hypocotyl gravitropism that has been observed in seedlings grown in darkness or white light. We report here that cytokinin at micromolar concentrations restores gravitropism to seedlings grown under red light. Cytokinin cancels the effect of red light on the gravity-sensing system and at the same time replaces light in the inhibition of hypocotyl elongation. Furthermore, application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid acts similarly to cytokinin. Cytokinin cannot restore gravitropism under red light to an ethylene-insensitive mutant that is defective at the EIN2 locus. Stimulation of ethylene production, therefore, can explain the action of cytokinin in restoring negative gravitropism to the hypocotyls of Arabidopsis seedlings grown under continuous red light.
细胞分裂素在双子叶植物幼苗的光形态建成的几个方面取代了光的作用。研究表明，在红光下生长的拟南芥幼苗会变得失去方向感，丧失在黑暗或白光下生长的幼苗中所观察到的下胚轴负向重力性。我们在此报告，微摩尔浓度的细胞分裂素可恢复在红光下生长的幼苗的重力性。细胞分裂素消除了红光对重力感应系统的影响，同时在抑制下胚轴伸长方面取代了光的作用。此外，乙烯前体1-氨基环丙烷-1-羧酸的应用与细胞分裂素的作用相似。细胞分裂素不能在红光下将重力性恢复到在EIN2位点有缺陷的乙烯不敏感突变体。因此，乙烯产生的刺激可以解释细胞分裂素在恢复连续红光下生长的拟南芥幼苗下胚轴的负向重力性方面的作用。
