Physiological Function of Night Interruption inLemna paucicostata6746: Action of Light as a Phaser on the Photoperiodic Clock

摘要

Flowering ofLemna paucicostata6746 under short-day conditions is completely inhibited by daily night interruption given to the“inhibition zone”that starts at Zeitgeber time (ZT) 14, i.e., 14 h after dawn, and ends 14 h before the next dusk [Oota (1983a)Plant&Cell Physiol. 24: 327]. With a modified min-SD method, most of these night interruptions were found to signal the false dawn (false ZT 0) after one entraining cycle. Thus, on and after day 2 the interruption was associated with the next main photoperiod to form a noninductive skeleton photoperiod. However, a light pulse applied at the start of the inhibition zone, caused no phase shift in the photoperiodic clock, and formed a noninductive skeleton photoperiod in association with the preceding main photoperiod.The complete floral inhibition due to the night interruption was ascribed to the illumination of both the LI-phase (real or false ZT 0) and L2-phase (real or false ZT 14), or the two light-sensitive fractions of the original or shifted critical photoperiod, by the thus formed skeleton photoperiod, just as was the case for the floral inhibition by complete photoperiods longer than the critical daylength, 14 h [Oota (1983a), Oota (1983b)Plant&Cell Physiol. 24: 15