Potassium Transport in Two Tomato Species

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Abstract
The commercial tomato, Lycopersicon esculentim Mill. cv. Walter, and its wild relative, Lycopersicon cheesmanii spp. minor (Hook.) C.H. Mull., were grown for 30 days under controlled conditions and in solution culture varying in its content of Na+ and K+. Subsequently, 86Rb-labeled K+ uptake and distribution were studied. From all solutions, ''Walter'' consistently absorbed 86Rb-labeled K+ at a higher rate in micromoles per gram fresh weight per 30 minutes than L. chessmanii. L. cheesmanii distributed a greater proportion of the absorbed K+ from its root to its shoot. When 0.6 millimolar NaNO3 replaced 0.6 millimolar KNO3 in the pretreatment solution, intact plants of both genotypes followed a similar pattern as when they were pretreated with K+ only, but a greater percentage of the absorbed K+ remained in the roots. Leaf slices of L. cheesmanii plants deprived of K+ for 6 days showed a greater rate of K+ uptake than did slices from ''Walter'' plants pretreated the same way. Stem slices of L. cheesmanii, however, had a lower uptake rate than did those of ''Walter''. Both leaf and stem slices of ''Walter'' plants, pretreated 6 days with 0.6 millimolar NaNO3 substituting for 0.6 millimolar KNO3 in their growth medium, had greater rates of 86Rb-labeled K+ uptake from 0.5 and 20 millimolar KCl solutions than did slices of L. cheesmanii. These marked differences in patterns of ion uptake and translocation indicate that these genotypes of tomato have evolved different mechanisms to deal with K+ and Na+ in their environments.