Effects of Calcium, Indoleacetic Acid & Distance From Stem Apex on Potassium & Rubidium Absorption by Excised Segments of Etiolated Pea Epicotyl

Abstract

A study was made of the effects of several factors on Rb86 labeled K uptake by excised segments of the 3d internode of etiolated pea seedlings (Pisum sativum var. Alaska) in KC1 solution. The measurements distinguished between the readily exchangeable and the less readily exchangeable (accumulated) fractions of K uptake. K uptake by older (2d cm) segments was enhanced by the presence of CaCl2 in the external solution after about 48 hours [long dash]but not in the younger upper (1st cm) segments. In the latter, however, 2,4-dichloro-phenoxy acetic acid (2, 4-D) at 1 ppm enhanced K uptake in the presence of external Ca relative to Ca solutions lacking 2,4-D. Enhancement of K uptake occurred also with SrCl2 but not in the presence of Cl salts of Ba, Mg, Mn, Fe, Al, or Na; the latter ions depressed K uptake.