Redistribution of 45ca in Trifolium Subterranevm L. and Antirrhinum Majus L.

Abstract

Injection of non-radioactive calcium into leaf 3 of normal- or low-Ca T. subterraneum plants immediately after transfer to tracer-free solutions caused changes in the distribution of Ca45 in the low-Ca plants only. In these plants the mean Ca45 concentration in the laminae of all leaves was appreciably increased as a result of the influx of Ca45 from the petioles. For both normal- and low-Ca plants 2 weeks growth in tracer-free solutions resulted in a reduction of the mean Ca45 concentration in both laminae and petioles of the old leaves, while the isotope appeared in new leaves produced during this period. A Ca injection at the end of this growth period caused a further reduction in mean Ca45 concentration in laminae and petioles of the old leaves, and movement of the isotope into the new leaves. This movement was mainly into the lamina center of the low-Ca and, to a much lesser degree, into the petioles of the normal-Ca leaves. Dialysis of Ca45 in leaf 2 showed that these changes in concentration of the isotope were restricted to the water-soluble fraction in the normal-Ca samples. In the low-Ca samples most of the change also occurred in the water-soluble fraction, but small changes were also recorded in the fractions extracted by sodium chloride, magnesium chloride, and hydrochloric acid. With A. majus plants a much greater redistribution of previously deposited Ca45 occurred in both original and new leaves of low-Ca plants transferred to tracer-free, normal-Ca solutions than in plants transferred to low-Ca solutions. Redistribution of Ca45 occurred also in normal-Ca plants transferred to normal-Ca solutions and to a lesser extent in normal plants transferred to low-Ca solutions. The redistribution of Ca45 continued between days 8 and 16 after transfer to tracer-free solutions. Ca45 artefacts were produced in autoradiographs by drying A. majus plants grown in normal but not in low-Ca nutrient solutions.