Growth and flowering responses of Lysimachia mauritiana Lam. to cold treatment and photoperiod

These studies were conducted to investigate the growth and flowering responses of Lysimachia mauritiana Lam. to photoperiod and cold treatment (Expt. 1) and to determine juvenility in floral induction (Expt. 2). In Expt. 1, eight-week-old seedlings with 4-6 leaves were treated with cold at 5 degrees C with a 9/15 (day/night) h photoperiod for 0, 3, 6, 9, and 12 weeks (wk). After cold treatment, plants were grown under five different photoperiods [9/15, 12/12, 14/10, 16/8, and 24/0 (day/night) h] for 15 weeks. Plants without cold treatment did not flower throughout the experimental period. However, after a 6-wk cold treatment, percent flowerings were 83 % and 82 % under 16/8 and 24/0 h photoperiods, respectively, and after 9- and 12-wk cold treatments both were 100 %. In Expt. 2, growth stages were divided into two groups according to the number of leaves: Stage 1 (4-6 leaves) and Stage 2 (10-12 leaves). Cold treatment was administered for 0-, 5-, and 10-wk at 5 degrees C with the same photoperiod treatments as Expt. 1. Flowering was not induced with cold treatment in Stage 1 for any photoperiod treatment. However, in Stage 2, percent flowerings were 40 % and 47 % after 5-wk cold treatments and 71 % and 91 % after 10-wk cold treatments under 16/8 and 24/0 h, respectively. These results indicate that a long-day photoperiod and sufficient cold exposure are necessary for flowering induction of L. mauritiana. This species also requires an appropriate growth stage to sense the forcing conditions.