Effects of interactions between low and high temperature treatments on flowering of spring rape (Brassica napus var. annua)

Exposure to high temperature (30 degrees C) before or after exposure to low temperature (0, 4 or 8 weeks at 4 degrees C) consistently increased the number of leaf nodes at flowering and delayed flowering in a range of genotypes of spring rape (Brassica napus var. annua L.). Four days of prior exposure to high temperature had more effect than 2 d, and the effect of subsequent exposure to high temperature was maximized when exposure commenced 1 week after the end of the low-temperature treatment. In genotypes that showed a vernalization response (i.e. in which the number of leaf nodes at flowering was reduced or flowering was advanced by low temperature), this response was reduced or eliminated by either prior high-temperature treatment (antivernalization) or subsequent high-temperature treatment (devernalization). A biochemical model to account for these effects is proposed. (C) 1998 Annals of Botany Company.