Accumulation of sugars in cucumber leaves during calcium starvation.

Abstract

To determine the metabolic role of calcium we grew cucumber plants without calcium. Symptoms of leaf injury such as chlorosis and marginal curling appeared a few days after the removal of calcium. The level of the soluble sugars in calcium deficient leaves increased to more than 10-fold that in the control at the late stage of treatment. In contrast, the level of the soluble sugars in the root decreased because of the calcium deficiency. The contents of soluble and bound calcium, in contrast to soluble sugars, decreased only in the young leaves of calcium deficient plants. The content of each soluble sugar measured by liquid chromatography was stable in the control leaves during treatment. Changes in sucrose, fructose, glucose, maltose and galactose in calcium deficient leaves were similar to the change in the total soluble sugars. The increases in stachyose and the mixture of raffinose and cellobiose took place only at the late stage of calcium starvation. The starch content in calcium deficient leaves was somewhat higher than that of the control, except for the remarkable decrease at the late stage. α-Amylase activities were not altered much in either the control or the calcium deficient plant during 5 days of treatment, but a clear increase took place at the late stage of calcium starvation. The reason for the distinct increase in the soluble sugars in calcium deficient leaves could be explained by the decline in transport due to the calcium deficiency.