4.3. Effect of photoperiod on growth and flowering
In the first experiment, the TDC plant height significantly increased at the time to first flower opening under longer pho-toperiods compared with SDs (10 h and 12 h) (Table 1). Zaccai andEdri (2002) found that the stem length of lisianthus ‘Heidi DeepBlue’ was enhanced under the LD treatment at day 60 when grownin either winter or summer. A similar increase in stem length wasalso found in C. lanceolata when exposed to an inductive LD treat-ment (Damann and Lyons, 1993). The significant increase in stemlength or plant height under LD conditions may be due to the longertime for carbohydrate production through photosynthesis or maybe due to an increase in endogenous GA, similar to Arabidops is plants (Hedden, 1999).Our results showed that the leaf number decreased under induc-tive LDs compared with SDs. The node number is equivalent to theleaf number. In other reports, in addition to the faster floral tran-sition under LD, the decrease in node number on the main stem at the first flower was described for lisianthus (Zaccai and Edri, 2002;Islam et al., 2005).In addition, branch number significantly increased under shorter photoperiods in this study, whereas the total number offlower buds was barely affected by different photoperiods (Table 1).Islam et al. (2005) also reported that continuous SD or a prolongedperiod in SD increased the number of branches. However, Islamfound that the number of flower buds was positively correlatedwith the branch number and was promoted by constant SD treat-ment. Inconsistency was also found in the research of Tsukada et al.(1982), in which SD-treatment retarded the development of lateralshoots compared with LD in lisianthus. It seems that the photope-riod effect on the branch number and the number of flower buds might be cultivar-dependant