EFFECTS OF GROWTH SUBSTANCES ON FROND AND FLOWER PRODUCTION IN LEMNA GIBBA G3

Frond and flower production in a long-day duckweed, Lemna gibbaG3, growing under different photoperiodic conditions in presenceand absence of varied concentrations of applied IAA, KIN andGA was investigated. The predominant actions of IAA, KIN and GA were revealed tobe respectively the depression of flowering, the promotion offrond multiplication and the enhancement of flowering. The rateof increase in FL % as an index of the concentration of floralstimulus in the tissues was curtailed greatly by IAA, to a lesserextent by KIN and little by GA. GA at 10^–5 M apparentlyreduced the critical day length (12 hr) and the induction period(48 hr) by 2 and 4 hr, respectively. No vegetative growth waspromoted by KIN in the light. On the basis of these and relevant findings the sites of actionof the growth substances examined in the flowering process ofthe duckweed were suggested. (Received May 30, 1965; )