Effects of Fluctuating Temperature on Germination and Emergence of Seeds in Different Moisture Environments

Abstract

Seeds of calabrese and carrot were sown in soil at different moisture contents or were germinated in polyethylene glycol solution of equivalent water potential. The seeds were also subjected to temperature environments which were either constant, altering at 12 h intervals, or changing smoothly and continuously in a daily cycle. The environments had similar mean temperatures, similar accumulated numbers of day-degrees, and the changing-temperature environments had similar upper and lower temperature limits. In soil, at low and moderate moisture stress, seedlings of both crops emerged faster in the changing-temperature environments than at constant temperature; at high moisture stress, emergence occurred only in the changing temperature environments. In osmotic solutions, germination (radicle emergence) of calabrese seeds was faster in changing-temperature environments, but germination of carrot seeds was unaffected by the temperature treatments. The results indicate that interaction between moisture stress and temperature environment is important and that results of experiments run at both constant moisture stress and constant temperature together may not relate directly to the field situation.