EFFECT OF VERNALIZATION, PHOTOPERIOD, AND LIGHT QUALITY ON THE FLOWERING PHENOTYPE OF ARABIDOPSIS PLANTS CONTAINING THE FRIGIDA GENE

We have compared the flowering response to vernalization, photoperiod, and far-red (FR) light of the Columbia (Col) and Landsberg erecta (Le r) ecotypes of Arabidopsis into which the flowering-time locus FRIGIDA (FRI) has been introgressed with that of the wild types Col, Ler, and San Feliu-2 (Sf-2). In the early-flowering parental ecotypes, Col and Ler, a large decrease in flowering time in response to vernalization was observed only under short-day conditions. However, Sf-2 and the Le r and Col genotypes containing FRI showed a strong response to vernali zation when grown in either long days or short days. Although vernaliz ation reduced the responsiveness to photoperiod, plants vernalized for more than 80 d still showed a slight photoperiod response. The effect of FRI on flowering was eliminated by 30 to 40 d of vernalization; su bsequently, the response to vernalization in both long days and short days was the same in Col and Ler with or without FRI. FR-light enrichm ent accelerated flowering in all ecotypes and introgressed lines. Howe ver, the FR-light effect was most conspicuous in the FRI-containing pl ants. Saturation of the vernalization effect eliminated the effect of FR light on flowering, although vernalization did not eliminate the in crease of petiole length in FR light.