Effects of bean seed production conditions on germination and hypocotyl elongation responses to temperature and water potential.

In order to test whether production conditions are responsible for variations in emergence behaviour between seed lots, germination and hypocotyl elongation responses to temperature and water potential were measured in the laboratory for bean (Phaseolus vulgaris L.) seed lots produced under different conditions. Germination and hypocotyl elongation responses were studied on eight seed lots in temperatures ranging from 10°C to 40°C, and the response of germination to water potentials ranging from 0 to -1 MPa was also observed. Germination rates differed most between seed lots at low (10°C) and supra-optimal (40°C) temperatures. Differences in germination rate at low temperatures could be explained by differences in germination base temperature (Tb). Hypocotyl elongation was almost nil at 10°C and 40°C, although germination was still observed. Base temperature was lower and varied more between seed lots for germination (3.5-8.9°C) than for hypocotyl elongation (7.8-9.1°C). Base water potential differed slightly between seed lots (-1.9 to -2.5 MPa) and was correlated with germination Tb. These differences in germination and hypocotyl elongation responses between seed lots are likely to lead to field emergence differences, especially at low temperatures.