Effect of pH on seedling growth of six cultivars of watermelon

Abstract

Watermelon [Citrullus lanatus (Thunb.) 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, 5.0, or 6.5. After 14 days, stem length, leaf area, leaf, shoot and root dry weight, and number of lateral roots were measured. Number of roots increased with increasing pH from 4.0 to 5.0 in all cultivars except DL and CG. The number of roots of CG decreased with increasing pH. The number of roots of MG and SB had positive linear and quadratic correlations, respectively, with increasing pH. In all cultivars, root dry weight decreased with increasing pH from 4.0 to 5.5. At pH ≤4.5, all cultivars except CG had short or no tap roots and thickened lateral roots. CG had a decrease in stem length, leaf dry weight and area, and shoot dry weight with increasing pH, and was sensitive to high pH. However, MG and SB had an increase in leaf dry weight and area with increasing pH, which suggested that MG and SB are sensitive to low pH. Although no differences in shoot parameters of 14‐day‐old plants were detected among CS, DL and JL, observations made 7 days after seeding indicated a possible pH effect on early growth of seedlings.