Biochemistry of the Photoperiodic Response the High-Intensity-Light Reaction

Abstract

A long dark period, in order to be photo inductive for a short-day plant, must be preceded by an appropriate period of high-intensity light. The component of the total photoperiodic reaction which is consummated in this light period, the high-intensity-light process, is the subject of this paper. The high-intensity-light requirement of Xanthium, a short-day plant, can be by-passed by artificial application of sucrose through the leaves or stems. Other sugars and Krebs cycle intermediates can also replace light in its role in the high-intensity-light process. The high-intensity-light process differs from the low-intensity-light process by which photo induction may be inhibited, both in energy requirement and in other characteristics. The 2 light-mediated component processes are therefore clearly distinct. The high-intensity-light process appears to be concerned principally with the production of substrates for respiration and the other processes which take place during an inductive dark period.