EFFECTS OF HUMIDITY AND CA LEVEL ON DRY-MATTER AND CA ACCUMULATION BY LEAVES OF CUCUMBER (CUCUMIS-SATIVUS L)

Two cucumber cultivars (Corona and Rebella) were grown under a range of day and night humidity combinations and at two levels of Ca (180 and 270 mg l-1) in the nutrient solution applied to the rockwool substrate. High humidity increased the incidence of Ca deficiency symptoms and decreased the dry weight of the leaves. The concentration of Ca (%) in the leaf dry matter was reduced by high humidity at night in Experiment A and equally by high humidity during the day or night in Experiment B. The response of the leaf tips (% Ca in the terminal 7 cm) was greater than that of the complete laminae, and similar to that of the total amount of Ca (mg) accumulated per complete lamina. Increasing the level of applied Ca increased the concentration of Ca (%) in the complete laminae and leaf tips, but the increase in total Ca per lamina (mg) was more marked. 'Corona' had heavier leaves than 'Rebella' and a higher concentration of Ca (%), resulting in a greater accumulation of Ca (mg) per leaf lamina.