PHOTOCONTROL OF GROWTH AND FLOWERING OF CARYOPTERIS

Abstract

P iringer , A. A., R. J. D owns , and H. A. B orthwick . (U. S. Dept. of Agriculture, ARS, Belts ville, Md.) Photocontrol of growth and flowering of Caryopteris . Amer. Jour. Bot. 50(1): 86–90. Illus. 1963.—Flower buds were initiated on plants of Caryopteris × clandonensis A. Simmonds (C. incana [Houtt.] Miq. × C. mongholica Bunge) on all photopcriods but developed to anthesis only when daily dark periods exceeded 8 hr. Anthesis occurred in not less than 22 days after the beginning of 11 or more short photoperiods. Treatments with short days could be interrupted by as many as 30 non‐inductive long days without significant increase in the minimum number of short days required for anthesis. Anthesis, like floral initiation of many plants, was reversibly controlled by red and far‐red radiation acting through phytochrome. The inductive effectiveness of long dark periods was nullified by 1 min of red light or about 1 hr of far red. It was modified by night temperature in the range 45–70.F and filament lengths of stamens were shorter at night temperatures of 60 than at 70 F.