Potassium Nutrition during Tomato Plant Development1

Abstract

Abstract K concentrations in xylem exudate and K concentrations and contents in stem, petiole, leaf lamina, and fruit tissues were determined at 10-day intervals during the development of field-grown tomato plants (Lycopersicon esculentum Mill.). Four determinate-type processing tomato cultivars were compared. Xylem exudate K+ concentrations of 9 to 12 meq/liter were measured prior to anthesis but declined to 7 to 8 meq/liter with the onset of fruiting. Vegetative growth rates were highest at 70 days after planting. Maximum rates of K accumulation in the plants occurred at 90 days, which coincided with the period of maximum K accumulation in the fruit. The rate of K accumulation in the plant relative to the shoot dry weight was correlated with the relative growth rate. About 70% of the K accumulated in the plant at harvest was taken up during fruiting. K redistribution from vegetative tissues contributed a maximum of only 12% of the total accumulated K by the fruit. K content in leaf lamina, petiole, and stem tissue decreased by about 20 to 40%, 20 to 30%, and 15%, respectively, during fruiting, depending on the cultivar.