INDUCTION OF LEAF SENESCENCE IN ARABIDOPSIS-THALIANA BY LONG DAYS THROUGH A LIGHT-DOSAGE EFFECT

Given the influence of photoperiod on reproductive development and who le-plant senescence in monocarpic plants, one would suspect that leaf senescence in these plants might be under photoperiodic control. In Ar abidopsis thaliana, which is monocarpic and also a nonobligate long-da y (LD) plant, LDs (16 h, 300 mu mol m(-2) s(-1)) caused leaves to die earlier than did short days (SDs, 10 h). Since leaf longevity was not par alleled by the reproductive development in the present study, the reproductive structures did not seem to be the primary controls of lea f senescence. The LD effect appeared to depend on the amount of light rather than on day length, for leaves given LDs at reduced light inten sity (180 mu mol m(-2) s(-1)) lived longer than those in LDs with full light. In addition, the higher light intensity promoted chlorophyll l oss and anthocyanin accumulation in LDs. Thus, senescence of these lea ves seems to be governed by light dosage rather than photoperiod. Ligh t may play a natural role in promoting the senescence of A. thaliana l eaves.