Population differentiation in Australian Cardamine. IV. Variation in flowering response

Abstract

Considerable variation in flowering time was observed among three altitudinal races of Cardamine gown under natural ccnditions at Canberra. This variation in flowering time was closely correlated with altitude, the low altitude race A being the earliest to flower and the alpine race C the latest.

Comparisons of the flowering responses of the three races under controlled environments showed that each of the races had specific temperature requirements for flowering which were related to the climatic regimes in their respective altitudinal ranges. The vernalization requirements of the low altitude race A were substantially less than those of race B, which were in turn less than those of race C. Likewise, the inhibitory effects of high post-vernalization temperatures were least pronounced in race A, intermediate in race B, and most pronounced in race C.

The adaptive signiticance of the variation in the climatic requirements for floral initiation among the three races is discussed.