Germination and vigour of black gram (Vigna mungo (L.) Hepper) seed from plants grown with and without boron

Abstract

Black gram (Vigna mungo (L.) Hepper) cv. Regur was grown to maturity in three potted soils [Badgingarra (Sl), Lancelin (S2) and Quailing (S3)] with (+B) or without (-B) added H3BO3. The subsequent germination and vigour of seeds from treated plants was tested by germinating them for 7 days with 2000 8M CaSO4 and 98M H3BO3and, for S2 and S3 only, by staining with tetrazolium. No symptoms of B deficiency were observed in plants on any soil:leaf B concentrations at early vegetative and flowering stages were above values regarded as critical for this species (7-8 mg kg-1). On S1, B depressed pod and seed dry matter (DM), weight per seed and % hard seed (14 v. 58); it enhanced % non-viable imbibed seed (18 v. 5) and abnormal seedlings (37 v. 2). On S2, -B had no effect on reproductive yield or % hard seed but increased the % abnormal seedlings (32 v. 0) and depressed the tetrazolium rating for seed vigour, and weight per seed. No effects of B were observed on seeds from plants grown on S3 soil. When considered over all replicates of all treatments, a B concentration of 6 mg kg-1 DM seed was critical for viability of imbibed seed and production of normal seedlings. The results suggest that the subsequent germination and morphology of seeds and seedlings are more sensitive to low B supply during seed production than are growth of the plant and the amount of seed produced. It is thus likely that black gram crops low in B but with no symptoms of B deficiency may produce seed with low % germination and a high % abnormality in their seedlings.