High Respiratory Activity of Guard Cell Protoplasts from Vicia faba L.

概要

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The rate of O_2 uptake was about 29 times higher in guard cell protoplasts (GCPs) than in mesophyll protoplasts (MCPs) on a Chl basis. The O_2 uptake was inhibited by respiratory inhibitors, but stimulated by respiratory uncouplers. On a Chl basis, the activities of Cyt c oxidase and NADH-Cyt c reductase, mitochondrial enzymes, were about 27 and 35 times higher in GCPs than in MCPs. On a Chl basis, the ATP content was about 9 times higher in GCPs. The amount of ATP in GCPs was decreased by respiratory inhibitors, an energy transfer inhibitor, and uncouplers of oxidative phosphorylation. On a volume basis, GCPs had 8- to 10-fold higher respiratory activities than MCPs, but had a low Chl content and lacked the activity of NADP-glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPD), the Calvin cycle enzyme. From these results, we concluded that oxidative phosphorylation plays a main role in ATP production in guard cells and that guard cells have a heterotrophic feature. Salicylhydroxamic acid (SHAM) in combination with KCN or NaN_3 strongly inhibited O_2 uptake, indicating the presence of cyanide-resistant respiration in guard cells. Phenylmercuric acetate (PMA), a potent inhibitor of stomatal opening, reduced the ATP content of GCPs by about 90%, whereas it had a relatively small effect on the ATP level of MCPs. The specific effect of PMA on GCPs is discussed.
日本植物生理学会の論文