Abstract: | The rates of CO2 incorporation into the epidermis of C. communiswere linear and were similar during the completion of opening(2 h) and closing (1 h) movements of stomata. The kinetics of14C turnover between metabolites and the rates of leakageof metabolites were determined for opening and closing movements.When stomata were opening there was a slow turnover of 14C frommalate chiefly into sugars. Upon stomatal closure 14C was initiallymainly in sugars, malate, and sugar phosphates. Thereafter,there was a slight loss of label from sugar phosphates witha corresponding increase in malate. Starch became labelled duringopening and closing movements. Rates of incorporation of CO2found in the leakage fraction were greatest whenstomata were opening. Of the labelled compounds Mostfrom the tissue, malate was the most highly labelled whetherstomata were opening or closing. Although interpretation of the turnover patterns is difficultwithout knowledge of pool sizes for the metabolites it is suggestedthat a pool of sugars exists within the guard cells, which havefairly direct and reversible access to carbon from starch andmalate. The implications of loss of malate from guard cellsduring stomatal opening and closing are discussed. |