STIMULATION OF THE SHIBATA SHIFT BY PHOTOCHROME IN THE COTYLEDONS OF THE MUSTARD SEEDLING SINAPIS ALBA L.

Abstract— In the cotyledons of the mustard seedling Sinapis alba L. the duration of the Shibata shift can be greatly shortened by a pretreatment with light pulses prior to the protochlorophyllide– chloro-phyllide a photoconversion. It was shown that the light pulses act through photochrome (P _fr ). Since reversibility of a red light pulse induction by a far-red light pulse is rapidly lost (within 2 min) it is concluded that at least the initial action of P_fr occurs rapidly in this response. On the other hand, the effect of a red light pulse on the rate of protochlorophyll regeneration in the mustard seedling cotyledons is fully reversible by a far-red light pulse for more than 5 min. It is concluded that control of protochlorophyll regeneration and control of the Shibata shift by phytochrome cannot be consequences of the same initial action of P_fr Apparently P_fr controls both phenomena independently.