Effects of Fluctuating Temperatures on Germination

TLDR: Comparisons of the germination of these species revealed distinctive differences which could be related to particular features of the geographical regions or ecological habitats in which they occur naturally.

Abstract: Germination responses to alternating daily cycles involving transfers between different temperatures over the range 0 to c. 40 °C were investigated in four species : Lycopus europaeus LClarkia unguiculata Lindl., Apium graveolens L. cv. Giant Red, and Suene dioica (L.) Clairv. Comparisons of the germination of these species revealed distinctive differences which could be related to particular features of the geographical regions or ecological habitats in which they occur naturally. The effects of fluctuating as opposed to constant temperatures varied from one species to another. L. europaeus depended almost absolutely on fluctuating temperatures for germina tion. Germination of S. dioica was greatly increased by fluctuating temperatures. Moderate increases occurred over a restricted temperature range in A. graveolens cv. Giant Red and C. unguiculata was affected in only minor ways. These results are discussed in relation to previous attempts to explain the mechanisms responsible for the frequently beneficial effects of fluctuating temperatures on germination.