Calcium Transport in Tomato Roots

Abstract

THE absorption of calcium by plant tissue generally has been considered to be a process involving metabolic uptake. Fried et al.¹, using excised barley roots, and Chasson and Levitt², using potato slices, found a rapid initial uptake of calcium-45 followed by a slower linear increase with time. The linear phase was interpreted to represent metabolic absorption of calcium at a constant rate. However, Moore et al.³, in experiments with excised barley roots, found that when the uptake of inert calcium was determined by chemical analysis, the linear phase increased only slightly with time. When the uptake of calcium-45 was measured, the increase in the linear phase was much more pronounced, presumably because of exchange of radioactive calcium for inert calcium present in the root tissues. In addition, calcium uptake was not reduced by low temperature or treatment with dinitrophenol. Consequently, Moore et al. concluded that in barley roots, calcium uptake was largely non-metabolic in the physiological pH range. Handley and Overstreet⁴ have reported that calcium uptake in primary roots of maize is non-metabolic in the meristematic portions of the root tip, but is largely metabolic in the older vacuolated portions of the root. In a recent examination of calcium accumulation in barley seedlings, Barber and Koontz⁵ concluded that metabolism was involved in the process by which calcium was eventually accumulated by the barley shoot.