Bimodal Floral Response of Lemna gibba G3 to Night Interruption : Photoperiodic Time Measurement

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Lemna gibba G3 (M-1% sucrose medium, 26℃) showed a bimodal floral response to a 2-hr light pulse scanning 21-, 18-, 15- and 12-hr nyctoperiods. With the simplified min-LD method, the light pulse given early or late in these nyctoperiods was found to signal false dusk or false dawn after two transient cycles. The magnitude of floral response to the light pulse depended on the length of the asymmetric skeleton photoperiod comprising either the preceding main photoperiod and the false dusk or the false dawn and the subsequent main photoperiod, No flower was induced by asymmetric skeleton photoperiods shorter than the critical daylength, 12 hr. In duckweed previously entrained to an interrupted 15-hr nyctoperiod, false dawn or false dusk was physiologically equivalent to the light-requiring L1- or L2-phase of the critical photoperiod. Another light-requiring phase occurred 12 hr after or before the false dawn or false dusk. These and relevant findings suggest that the timing of the L1 - and L2-phases is under the control of the endogenous circadian oscillator and that the skeleton as well as complete photo-periods are inductive only when both the L1- and L2-phases, whether they are shifted or not due to night interruption, are illuminated.
日本植物生理学会の論文