Role of Calcium in Phytochrome-Controlled Nyctinastic Movements of Albizzia lophantha Leaflets

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Abstract
The involvement of Ca2+ on phytochrome-controlled nyctinastic closure in Albizzia lophantha has been studied by testing the effect of the calcium ionophore 6S-[6.alpha.(2S*,3S*),8.beta.(R*),9.beta.,11.alpha.]-5-methyl-amino)-2-[[3,9,11-trimethyl-8-[1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl]-1,7-dioxaspiro[5.5]-undec-2yl] methyl]-4-benzoxazolecarboxylic acid (A23187) and the intracellular calcium antagonist 8-(diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8). An external supply of Ca2+ or calcium ionophore A23187 to the Albizzia leaflets emulates the effect of red light irradiation and counteracts the inhibitory effect of far red light. The intracellular calcium antagonist TMB-8 supplied to Albizzia leaflets inhibits the effect of red light, but had no effect on far red irradiated plants. This suggests a dependence between phytochrome action and intracellular free Ca2+. We suggest that calcium acts as a phytochrome messenger on control of ion fluxes that drive turgor changes in pulvinular motor cells.