Laboratory and greenhouse experiments were conducted to determine the effect of light, temperature, solution pH, solution osmotic potential, and oxygen concentration on pitted morningglory germination and radicle plus hypocotyl elongation, and seeding depth on its subsequent emergence. Daily exposure of seed to natural light resulted in lower germination than in darkness, whereas germination was not influenced by brief exposure to red or far-red light. Germination occurred over a wide range of constant temperatures, from 7.5 to 52.5 C, with optimum germination between 20 and 25 C. Germination occurred at solution pH range of 3 to 10 and was optimal from pH 6 to 8. Radicle plus hypocotyl elongation was influenced by the interaction of temperature and solution pH. A combination of acidic medium (pH 6) and high temperature (30 C) resulted in the greatest radicle plus hypocotyl length of 7.6 cm after a 7-d incubation. Germination and radicle plus hypocotyl elongation, averaged over the 15 and 30 C temperature, decreased with increasing moisture stress, with less than 3% normalized germination at −1.0 MPa. Germination was 29, 40, and 51% at 2, 10, and 20% oxygen, respectively, averaged over 15 and 30 C. Germination of seed lying on the soil surface covered with filter paper or without any cover was similar, averaging 64%. Normalized emergence, relative to germination on the soil surface, decreased with increasing burial depth to 4% emergence at 10 cm, with a mean emergence depth of 4.1 cm, averaged across two soil types.

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.