CALCIUM-DROUGHT INTERACTIONS ON CARBON STRATEGY, MEMBRANE DISORDERS AND SOME RELATED METABOLIC PROCESSES OF HELIANTHUS ANNUUS L., VICIA FABAL. AND ZEA MAYS L

Abstract

This work was planned to record and evaluate the ameliorative effect of supplemental Ca?° on three water-stressed crop plants, namely, sunflower, broad bean, and maize plants. Growth, some major physiological process, cell wall composition, some metabolic pools and mineral contents were followed in the test plants representing vanous categories of crops (oil-protein- and starch-accumulating plants).

The results obtained from this work could be summarized mn the following main points:

1- Water stress induced a considerable reduction in transpiration of broad bean plants, while that of sunflower or maize was unaffected. The response to supplemental Ca?, ranged from significant acceleration in maize to significant decline in sunflower; that of broad bean plants had not been affected. Due to the reduction in transpiration rate, the relative water content of shoots or roots of plants was in most cases raised, with the decrease in soil moisture content, while it was mostly lowered by • supplemental Cat. Generally, a positive correlation between relative water content and respiration rate can be ruled out.

2- Fresh and dry masses of the experimental plants were significantly reduced with the decreased soil moisture content. Calcium treatments significantly increased both fresh and dry weights in most cases despite variable responses to the various combinations. Leaf area of sunflower or maize plants was excessively reduced with the decrease in soil moisture content while that of broad bean was unaffected. Application of Ca2 ... resulted mostly in a considerable increase in the leaf area of the test plants.