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KMID : 0368419930360040383
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Journal of Plant Biology
1993 Volume.36 No. 4 p.383 ~ p.389
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Influence of the Mesophyll on the Change of Electrical Potential Difference of Guard Cells Induced by Red-light and CO_2 in Commelina communis L. and Tradescantia virginiana L.
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Lee, Joon-Sang/李俊商
Bowling, D.J.F.
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Abstract
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The effects of light and CO_2 on the electrophysiological characteristics of guard cells in the intact leaf and in the detached epidermis have been investigated. Guard cells in intact leaves showed the membrane hyperpolarization in response to light. The biggest induced change of the membrane potential difference (PD) in the guard cells of the intact leaf was 13 mV by light and 42 mV by CO_2 in Commelina communis. Similar results were obtained with Tradescantia virginiana. However, there were no changes of membrane PD in detached epidermis. In order to determine the influence of the mesophyll on the changes of membrane PD, infiltration of the mesophyll cells with photosynthetic inhibitors was performed. In CCCP infiltrated leaf discs the guard cell membrane was depolarized slightly by red-light and hyperpolarized by CO_2 but in leaf discs infiltrated with DCCD and DCMU the guard cell membrane was hyperpolrized by both red-light and CO_2 as the control leaf discs. In azide infiltrated leaf discs the guard cell membrane showed no response to light and there was a much reduced membrane hyperpolarization by CO_2 compared to other responses. It was likely that azide caused leaf damage and the activity of cell metabolism was decreased greatly, resulting in small membrane PD changes by CO_2 and no changes by red-light. Therefore, it can be suggested that red light was sensed by the mesophyll and the light induced guard cell membrane hyperpolarization was related to energy produced by cyclic-photophosphorylation, but CO_2-induced guard cell membrane hyperpolarization was not related to photosynthesis. Alkalisation of the vacuole was observed when the intact leaf was exposed to CO_2 indicating that membrane hyperpolarization was mainly the result of proton efflux.
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