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 tim e 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 r elationship between these two traits depended strongly on nutrient sup ply. A lower nutrient supply first led to an extension of the vegetati ve phase, while the mean number of leaves at flowering was hardly affe cted. A further reduction resulted in no further extension of the vege tative phase and, on average, plants started flowering with a lower le af number. At low nutrients, early flowering affected the timing of pr oduction of siliques rather than the total output, whereas late flower ing was favorable at high nutrients. This may explain the fact that ma ny plant species flower at a relatively small size under poor conditio ns. Flowering time genes had pleiotropic effects on the leaf length, n umber of rosette and cauline leaves, and number of axillary flowering shoots of the main inflorescence. Silique production was positively co rrelated with the number of axillary shoots of the main inflorescence; the number of axillary primordia appeared to have a large impact on r eproductive yield.