Effects of Osmotic Stress, Ionic Stress and IAA on the Cell-Membrane Resistance of Vigna Hypocotyls |
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Authors: | Liu Qiang; Katou Kiyoshi; Okamoto Hisashi |
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Institution: | Biological Institute, Faculty of Science, Nagoya University Furo-Cho, Chikusa-ku, Nagoya, 464-01 Japan |
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Abstract: | The cell-membrane resistance (Rm) of Vigna hypocotyls was examined,and the effects of osmotic stress, ionic stress and IAA on Rmwere investigated. Rm decreased by 64 to 77% under osmotic stressin the presence of absorbable solutes (40 mM sorbitol, 15 mMKC1, 30 mM sucrose; or 40 mM sorbitol, 15 mM KC1, 30 mM sucroseplus 104 M IAA) or under ionic stress (50 mM NaCl or50 mM KC1). Rm was not changed by perfusion with 104M IAA. Therefore, the hyper-polarizations of the membrane potentialobserved in both cases should be ascribed totally to the activationof the electrogenic proton pump. Although Rm showed an increaseof 1.6 fold when the hypocotyls were subjected to osmotic stress(100 mM sorbitol or 100 mM sorbitol plus 104 M IAA),83.6% or 92.4% of the hyperpolarization of the membrane potential(Vpx was also the result of the activation of the pump. Theresults, calculated on the basis of the current source model,support the viewpoint that the hyperpolarization of the cellmembrane potential of Vigna hypocotyls under osmotic stress,ionic stress or in the presence of IAA is an expression of theactivation of the proton pump, and is not caused by an increasein Rm.
1 Present address: Researchers and Planners of Natural Environment, Yotsugi Bldg. (2F), 1-5-4 Horinouchi, Suginami-Ku, Tokyo,166 Japan
2 Present address: Graduate School of Integrated Science, YokohamaCity University, 22-2 Seto, Kanazawa-Ku, Yokohama, 236 Japan (Received February 14, 1991; Accepted July 24, 1991) |
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