Sicklepod (<i>Senna obtusifolia</i>) germination and emergence as affected by environmental factors and seeding depth

Abstract

Laboratory and greenhouse experiments were conducted to determine the effect of light, temperature, solution pH, solution osmotic potential, and oxygen concentration on sicklepod germination and radicle plus hypocotyl elongation and seeding depth on emergence. Scarified, nondormant sicklepod seeds were used for these experiments. Sicklepod germination was not influenced by red or far-red light nor was light required for germination, which averaged 81% over all light treatments. Sicklepod germinated over a range of constant temperatures from 15 to 50 C, with optimum germination between 15 and 30 C. Germination was optimal near pH 6 for temperatures of 15 and 30 C. Germination and radicle plus hypocotyl length decreased with decreasing solution osmotic potential, and no germination occurred at a solution osmotic potential of −0.75 MPa at 15 C during 7 d incubation. Germination was greater at 20% oxygen than at 2% oxygen. The mean emergence depth for sicklepod was 3.3 and 4.6 cm in a highly disturbed sand and sandy loam soil, respectively. Sicklepod emerged from a 10-cm depth in the sandy loam soil, but no emergence occurred in the sand soil at this depth.