Growth and Boron Uptake of Five Pecan Cultivar Seedlings

Abstract

Growth and B uptake of five pecan [Carya illinoensis (Wangenh.) C. Koch] seedling cultivars were evaluated in two greenhouse experiments. Seedlings were exposed for 7 to 8 months to various B-containing irrigation solutions. In one study, the growth of `Apache', `Riverside', and `Burkett' seedlings declined significantly with a 5.0-mg B/liter application that provided 12.3 mg B/liter in the soil saturation extract. In the second study, B application of 2.5 mg·1iter -1 (6.4 mg·liter -1 in the saturation extract) reduced growth of `Western' and Wichita' seedlings. Seedling sources differed in susceptibility to B applications. `Apache' and `Wichita' seedlings were the more sensitive cultivars in the experiments. Leaf B concentrations increased linearly with concentrations in the saturation extract (r = 0.96 to 0.99), but did not depend on the cultivar. Boron toxicity (leaf interveinal chlorosis and tip necrosis) occurred within several weeks following B application of 1.25 to 2.5 mg·liter -1 (2.8 to 6.6 mg·liter -1 in the saturation extract, depending on cultivar). Three months later, chlorotic areas became necrotic in leaves containing >900 mg B/kg dry weight. Severe necrosis and some defoliation occurred when B concentrations were increased further. Leaves with no injury contained ≤325 mg B/kg.