水耕培養液中の鉄濃度がそ菜の銅過剰障害に及ぼす影響

Abstract

Bean, spinach, lettuce, and radish were grown in solution culture to investigate the effect of Fe concentration in the nutrient solution on Cu toxicities. Hoagland′s No. 1 solution was used as the basic nutrient solution. Copper was supplied at levels of 0.02, 0.3, 1, and 3ppm. At each Cu level Fe was supplied as Fe-EDTA at rates of 1, 3, 10, and 30ppm. The pH of the nutrient solution was adjusted to 5.1. At Fe 1ppm increasing Cu supply resulted in severe growth inhibition, and Cu 1 and 3ppm induced interveinal chlorosis on upper leaves except for lettuce. At the normal Cu level (0.02ppm), Fe 1ppm was sufficient for normal growth and a high level of Fe exceeding 10ppm was unnecessary or injurious. At Cu 0.3 and 1ppm, however, increasing Fe supply up to 3 or 10ppm was effective in alleviating the growth reduction and preventing the occurrence of chlorosis, especially in bean and spinach. At Cu 3ppm, where each of the crops showed severe dying off of older leaves and brownish discoloration of roots, increasing Fe supply prevented the occurrence of chlorosis but showed little effect in alleviating the growth reduction.2. The effect of increasing Fe supply at a suitable rate to reduce the Cu toxicity was considered to be due to the suppression of Cu accumulation especially in roots. The occurrence of chlorosis was associated with lowered concentration of 1N HCl soluble Fe in leaves, which suggested the precipitation of Fe in leaves.