CO2 FIXATION, ORGANIC ACIDS AND SOME ENZYMES IN GREEN AND COLOURLESS TISSUE CULTURES OE KALANCHOË CRENATA

Abstract

SummaryMeasurements of gaseous exchange between green callus tissue cultures of Kalanchoe crenata and air showed that photosynthesis occurred in the green callus. Feeding experiments with 14CO2 showed that 14C was incorporated by green callus into sugars and sugar phosphates in the light, and some 14C was incorporated into organic acids. Organic acids were the main products of dark fixation of 14CO2 by green callus but no activity was detected in sugars or sugar phosphates. The products of 14CO2 fixation in colourless callus were primarily organic acids both in the light and dark and no activity was detected in sugars or sugar phosphates.Green callus did not show a diurnal fluctuation of acid content. This, coupled with the observations that green callus did not show a net fixation of CO2 in the dark, suggested that the green callus did not exhibit crassulacean acid metabolism. Green callus, however, contained greater quantities of malate, citrate and isocitrate than did colourless callus. Enzyme assays suggested that the presence of PEP carboxylase in green callus and its absence in colourless callus might in part contribute to the higher acid levels of green callus.