EFFECTS OF ROOT ZONE PH AND NUTRIENT CONCENTRATION ON THE GROWTH AND NUTRIENT UPTAKE OF TOMATO SEEDLINGS

Abstract

The effects of nutrient concentration and pH, two major chemical properties of soil, on plant responses were investigated with seedlings of tomato, which is widely grown in greenhouses, as the model plant. An experiment with four levels of nutrient concentration [None (NC 0), 1 (NC 1), 5 (NC 5), and 10 folds (NC 10)], in combination with three pH levels (4, 6, and 8), was conducted. The fresh and dry weight and leaf area of tomato seedling increased until NC5, but decreased at NC10. Transpiration rates, stomatal conductance, and evapotranspiration reduced with increasing nutrient concentration. The responses to the pH levels differed by the nutrient-concentration levels. The unsuitable root zone pH, pH 4 and pH 8, caused more reductions of transpiration rates, stomatal conductance, and evapotranspiration than pH 6 does under high nutrient concentrations, specifically pH 8 strongly depressed these. At pH 8, fresh and dry weight and areas of shoot and root sharply reduced more than at pH 4. Total nitrogen (N) content in shoot and root was not significantly affected by pHs and nutrient concentrations. High pH and high nutrient concentration level increased magnesium uptake, but decreased calcium uptake. The contents of microelements decreased as nutrient concentration increased. Changes of macro and micro element content among treatments were smaller in shoot than in root. The results imply that not only nutrient concentration but also root zone pH is associated with osmotic stress, and tomato seedlings have a tendency to reduce shoot more than root against the stress. However, nutrient contents of shoot are maintained over a certain level and surplus nutrients are stored at the root.