Induction of leaf senescence in Arabidopsis thaliana by long days through a light-dosage effect

Given the influence of photoperiod on reproductive development and whole-plant senescence in monocarpic plants, one would suspect that leaf senescence in these plants might be under photoperiodic control.In Arabidopsis ihaliana, which is monocarpic and also a nonobligate long-day (LD) plant, LDs (16 h.300 pmol m"' s"') caused leaves to die earlier than did short days (SDs, 10 h).Since leaf longevity was not paralleled by the reproductive development in the present study, the reproductive structures did not seem to be the primary controls of leaf senescence.The LD effect appeared to depend on the amount of'light rather than on day length, for leaves given LDs at reduced light intensity (180 pmol m'"s"') lived longer than those in LDs with full light.In addition, the higher light intensity promoted chlorophyll loss and anthocvanin accumulation in LDs.Thus, senescence of these leaves seems tO' be governed by light dosage rather than photoperiod.Light may play a natural role in promoting the senescence of A. thaiiana leaves.