EFFECT OF pH ON ROOT GROWTH OF SIX CULTIVARS OF WATERMELON

Abstract

Watermelon [Citrullus lanatus (Thumb) Matsum and Nakai] cultivars Charleston Gray(CG), Crimson Sweet(CS), Dixielee(DL), Jubilee(JL), Mirage(MG) and Starbrite(SB) were grown in white quartz flintshot sand and watered daily with 0.01M sodium acetate buffer at pH 4.0, 4.5, 5.0, 5.5, 6.0, or 6.5. After two weeks, stem length, leaf area, leaf and root dry weight, and root number were measured. Nnumber of root decreased with decreasing pH below pH 5.0 in all cultivars except CG, which had an increase trend. Root number of MG and SB had negative linear and quadratic correlations respectively, with decreasing pH. In all cultivars, root dry weight increased with decreasing pH below pH 5.5. Under pH≤4.5, all cultivars except CG, had short or no tap root and thickened lateral roots. CG had a decrease in stem length, leaf dry weight and leaf area with increasing pH, and was sensitive to high pH. However, MG and SB had reduction in leaf area and stem length with decreasing pH, which suggests that MG and SB are sensitive to low pH. Although there were no differences in shoot parameters of 2wk-old plants of CS, DL and JL, observations made at 7 days after seeding indicated a possible pH effect on early growth of seedling.