Effects of Chelation and of Certain Cations on the Mobility of Foliar-Applied 45ca in Stock, Broad Bean, Peas, and Subterranean Clover

Abstract

A series of water-culture experiments was conducted with broad bean (Vicia faba L.), common stock (Mathiola incana R. Br.), subterranean clover (Trifolium subterraneum L.), and garden peas (Pisum sativum L.) grown in normal- and low-calcium nutrient solutions. Leaves of the plants were either injected or surface-treated with an aqueous solution of Ca45Cl2 with and without various additions to the dose. The subsequent distribution of Ca45 in the plants was determined by means of radio-autographs and radioassays. In each species, where nothing was added to the dose, there was negligible movement of Ca45 from the treated leaf. With broad bean or common stock or both, the addition of small amounts of EDTA (disodium salt) or HC1 or both, or of citric acid, causes marked movement of Ca45 in an acropetal direction in both the normal and calcium-deficient plants. Marked accumulation of Ca45 occurred in the epidermal hairs and anthers of common stock. There was also some evidence of retranslocation of Ca45 in this species. A series of experiments with subterranean clover confirmed the effect of EDTA in promoting mobility of Ca45 when either injected into a leaf or applied to the uninjured leaf surface. With low concentrations of EDTA, movement was mainly acropetal, but with a high concentration marked basipetal movement to the roots also occurred. When graduated amounts of non-radioactive calcium (as CaCl2.6H2O) or equivalent amounts of magnesium (as MgCl2.6H2O) were added to the dose, increasing mobility of the injected Ca45 occurred in both normal and calcium-deficient plants. With the highest levels of calcium or magnesium additions, movement of Ca45 occurred throughout the plant including the cotyledons and the whole of the root system.