Abstract
Young plants of cucumber (Cucumis sativus L.) cultivars, ‘Suyô’and ‘Kurumeochiai H’, widely used as summer and spring crops respectively, figleaf gound (Cucurbita ficifolia Bouché) and ‘Suyô’ grafted on figleaf gourd were grown for 10 days in a third strength Hoagland No.1 solution kept at 12, 14, 17, 20, 25 and 30°C. Growth of ‘Suyô’ was severely suppressed at 12 and 14°C, while that of ‘Kurumeochiai H’ was suppressed at 12°C. Figleaf gourd showed a high ability to toleratelow root temperatures. Growth of ‘Suyô’ at lower root temperatures was significantly improved when grafted on figleaf gourd. The difference in growth response between cucumber and figleaf gourd was most remarkable in the roots. Thus, at lower root temperatures, the root growth was suppressed greatly in both cucumber cultivars, whereas it was promoted in figleaf gourd. Leaf water content decreased at lower root temperatures, and the decrease was most marked in ‘Suyô’. Chlorosis occurred at lower root temperatures on the leaves which expanded after the beginning of root temperature treatment, and most pronounced in ‘Suyô’ at 12°C, where the plant growth was severely depressed. Low root temperature reduced nutrient concentrations of leaves, and it was particularly true for P and Mn. When the 4 crops were included, highly significant correlations were observed between the degrees of growth suppression and decrease in the nutrient concentrations of leaves, particularly in N, P and K.
