Endogene Rhythmik und photoperiodische Blühinduktion beiKalanchoe

Abstract

A. Ipomoea coccinea. 1. It is possible to induce flowering of this short-day-plant with a single dark period of sufficient length (10 hours) even in the seedling stage. 2. The number of induced flower buds increases with the length of the dark period till an upper limit, which is reached after about 30 hours of darkness. B. Kalanchoe blosfeldiana 1. The flowering effect shows a rhythmical pattern depending upon the length of a dark period, which is given before a basic induction of 5 short days. 2. The flowering effect shows also a rhythmical pattern, if the plants get a red light-interruption (660 k erg cm−2) in a 62-hour-dark period. The flower induction is inhibited in the scotophil phase and promoted in the photophil phase when compared to the dark control (fig. 7). 3. Far red interruptions (180 k erg cm−2) in the first 30 hours of a 62-hour-dark period inhibits the flower induction. Later it decreases the inhibition (fig. 8). 4. The opening and closing movements of the petals under corresponding conditions (as described under 1. und 2.) can be shown to take a course parallel to the rhythmical phenomenon of flower induction by light interruptions.