Pleiotropic effects of flowering time genes in the annual crucifer Arabidopsis thaliana (Brassicaceae)

Variation in flowering time of Arabidopsis thaliana was studied in an experiment with mutant lines. The pleiotropic effects of flowering time genes on morphology and reproductive yield were assessed under three levels of nutrient supply. At all nutrient levels flowering time and number of rosette leaves at flowering varied among mutant lines. The relationship between these two traits depended strongly on nutrient supply. A lower nutrient supply first led to an extension of the vegetative phase, while the mean number of leaves at flowering was hardly affected. A further reduction resulted in no further extension of the vegetative phase and, on average, plants started flowering with a lower leaf number. At low nutrients, early flowering affected the timing of production of siliques rather than the total output, whereas late flowering was favorable at high nutrients. This may explain the fact that many plant species flower at a relatively small size under poor conditions. Flowering time genes had pleiotropic effects on the leaf length, number of rosette and cauline leaves, and number of axillary flowering shoots of the main inflorescence. Silique production was positively correlated with the number of axillary shoots of the main inflorescence; the number of axillary primordia appeared to have a large impact on reproductive yield.