Some Biochemical Characteristics of Guard Cell and Mesophyll Cell Protoplasts fromCommelina communisL.

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Abstract
Guard cell and mesophyll cell protoplasts of Commelina communis L., were isolated and used to investigate their various biochemical characteristics. Contamination of the samples by other cell types was very low and viability of the protoplasts, assessed by the use of neutral red, Evans blue and fluorescein diacetate, was high (89–98%). Mesophyll cell protoplasts contained more chlorophyll (× 47), more soluble protein (× 10), more total N (× 36) and more DNA (× 9) than guard cell protoplasts. The absorption spectra of protoplast extracts were similar for both cell types except that below 400 nm there was a large increase in absorption by the guard cell protoplast extract. In guard cell protoplast extracts, high levels of activity of phosphoenolpyruvate carboxylase (E.C. 4.1.1.31), NAD malate dehydrogenase (E.C. 1.1,1.37), NADP malic enzyme (E.C. 1.1.1.40) and carbonic anhydrase (E.C. 4.2.1.1) were detected while only low levels of pyruvate-orthophosphate dikinase (E.C. 2.7.9.1) activity were detected. Glycollate oxidase (E.C. 1.1.3.1), ribulose-l,5-bisphosphate carboxylase (E.C 4.1.1.39), NADP malate dehydrogenase (E.C. 1.1.1.82) and NAD malic enzyme (E.C. 1.1.1.39) were not detected in guard cell protoplast extracts. High levels of ribulose-1, 5-bisphosphate carboxylase, glycollate oxidase, NAD malate dehydrogenase and carbonic anhydrase were detected in mesophyll cell protoplast extracts which is typical of C3 plants. A pathway of carbon flow during stomatal opening and closing is proposed.