[Effect of water stress on phosphoenolpyruvate carboxylase activity in Mesembryanthemum crystallinum (L.)].

Four-and-a-half-week-old plants of Mesembryanthemum crystallinum (L.) were transferred to cooled nutrient solution or to nutrient solution of low oxygen content. These stress treatments are known to reduce the absorption of water by plants. Examination of the second foliar leaves showed that the stress treatments result in a malate accumulation in the leaf mesophyll during the night which is paralleled by a drastically increased activity of phosphoenolpyruvate carboxylase. The results are discussed in relation to alterations of leaf growth, leaf water content and leaf water saturation deficit of the plants treated as described.