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High respiratory activity of guard cell protoplasts from Vicia faba L.
by Shimazaki K.-I., Gotow K., Sakaki T., Kondo N. (1983)
in Plant Cell Physiol 24: 1049-1056 – DOI: https://doi.org/10.1093/oxfordjournals.pcp.a076607 –
On a Chi 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 Chi 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 Chi 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 NaN3 strongly inhibited O2uptake, 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.