Abstract
Eight species of vegetable crops were grown in solution culture in order to investigate the effect of potassium and calcium concentration in the nutrient solution on zinc toxicities in vegetable crops. Zinc was supplied at levels of 0.05, 3, and 10ppm. At each zinc level potassium or calcium was supplied at rates of 2, 6, and 18me/l. The pH of the nutrient solution was adjusted to 5.0. Plants were grown under different treatments for about three weeks.
1. Zinc excess induced interveinal chlorosis on upper leaves in bean, cucumber, eggplant, pepper, cabbage, and spinach. In lettuce and celery chlorosis was induced on lower leaves. Increasing the supply of potassium and calcium reduced the severity of zinc-induced chlorosis. There was not so marked difference between the beneficial effect of potassium and that of calcium.
2. Increasing the supply of potassium and calcium was effective in alleviating the growth reduction of vegetable crops due to zinc excess. This effect was generally more marked with calcium than with potassium.
3. With increasing zinc level in the nutrient solution the zinc concentration in leaves of vegetable crops increased. Increasing the supply of potassium and calcium suppressed excessive accumulation of zinc in leaves. The influence of calcium was generally stronger than that of potassium. In any vegetable crops, regardless of potassium and calcium treatments, zinc concentration in leaves was closely related to the growth reduction due to zinc toxicities.
