Effects of Exogenous Auxin on the Regulation of Elongation Growth of Excised Segments of Vigna Hypocotyls under Osmotic Stress

IAA applied simultaneously with osmotica greatly enhanced theadaptive recovery of the elongation growth of segments of Vignahypocotyls during osmotic stress irrespective of whether ornot absorbable solutes were present. IAA stimulated both thesurface pump and the xylem pump, which have been shown to bestimulated by osmotic stress and to control the yielding ofthe cell wall and the absorption of solutes. Thus, wall extensibilityand the effective turgor were further enhanced under osmoticstress in the presence of IAA. These results indicate that thesimultaneous presence of IAA can reduce the inhibition of growthby osmotic stress, and they support numerical predictions basedon the apoplast canal model. The mechanism involved in the rapidrecovery of growth is discussed. ¹ Present address: Research Centre, Guangxi Agricultural University,Xiu Ling Rd., Nanning, Guangxi 530005 China. ² Present address: Biology Institute, Department of GeneralEducation, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya,464 Japan. ³ Present address: Graduate School of Integrated Science, YokohamaCity University, 22-2, Seto, Kanazawa-ku, Yokohama, 236 Japan.