Abstract— The strong effect of light pretreatments on the synthesis of chlorophyll‐a and‐b in the shoot of Sorghum vulgare (kept under saturating white light) can be attributed to phytochrome only. No specific blue light effect was found. The phytochrome system appears to function perfectly normally under these conditions. Escape from reversibility is not detectable up to approximately 40 min after the onset of an inductive red light pulse. Thereafter, escape is fast, being completed at approximately 2.5 h after the inductive light pulse.

Flowering was induced in Zinnia elegans under non-inductive 24-h photoperiods by the application of gibberellic acid, although later than under inductive 8-h photoperiods. Gibberellic acid also enhanced extension growth and leaf differentiation under both photoperiods.

No abstract

A. caudatus f. albiflorus, A. caudatus f. caudatus and A. tricolor var. tristis are qualitative SD plants with photo-inductive requirements of six, three and five, 8-hr photoperiodic cycles, respectively, for macroscopic inflorescence initiation. The total protein content gradually increased in both stem and leaves with an increasing number of inductive photoperiodic cycles. In both stem and leaves of all three plant types, two electrophoretically separable new water-soluble protein bands appeared with completion of their respective photo-inductive requirements for inflorescence initiation. In the stem of A. caudatus f. caudatus, a third band appeared after the plants had received only a single SD cycle. The new proteins formed concurrently with photoperiodic floral induction differed electrophoretically from plant to plant even though all plants used in the experiment were short-day plants and closely related taxonomically.

S U M MARYFloral buds were induced either by 8 h photoperiods or by the application of GA3 and GA13 in Impatiens bahamina. Total enzyme activity was not directly related to floral morphogenesis although some interesting qualitative correlations existed. Thus, the presence of a new isoenzyme of amylase {Rp 0-05) may be related to flower formation since it was present only in the induced plants and not in the vegetative ones, regardless of whether the ffowering was caused by inductive photoperiods or by gibberellin treatment. Catalase activity', as well as its isoenzyme forms, could not be detected in the stem and the isoenzyme profile in leaves did not alter with photoperiodic or gibberellin treatment. Treatment with gibberellins induced the synthesis of new isoenzymes of peroxidase but inductive photoperiods did not. The enzyme profiles in relation to photoperiod and gibberellin application are discussed.