The Interrelation between CO2 Metabolism and Photoperiodism in Kalanchoë. II. Effect of Prolonged Darkness and High Temperatures

Abstract

As previously reported, when plants of Kalanchoe blossfeldiana are given a series of short day and long night cycles they show an increased uptake of CO2 in the dark and an increased production of CO2 in the light. In order to ascertain the nature of the production of CO2 in light, plants of Kalanchoe, previously exposed to short days, were allowed to fix CO2 2 was evolved. On now exposing to light at 20[degree] C a further (smaller) evolution of CO2 occurred. It is deduced that the dark fixation product comprises both thermo-labile and photo-labile fractions. Plants given the min. number of short-day cycles to induce flowering, but kept at different temps. during the dark period, showed a decreased flowering response at high temps. (30 and 35[degree] C ). This suggests that the product of the dark fixation of CO2 may be causally related to flowering. Exposure to a single very long dark period causes little or no CO2 fixation, and correspondingly there is little or no CO2 evolution on subsequent exposure to light.