Abstract
The effect of photoperiod on the distributing pattern of flower buds along a stem and the growth of leaves in Trapa bispinosa Roxb. was examined by the photoperiodic treatments of seven artificially changed day-lengths, 9, 11, 13, 13.5, 14, 15, 17 hours in 24 hours cycle. The treatments were conducted for two months, from 26th June to 26th August, using the plants in the late floating leaf stage. Flower buds initiated under the short-day conditions of 14 hours or less. The distributing pattern of flower buds formed along a stem under the short-day condition was affected by photoperiod ; that is the number of flower nodes (FN) in a flower node group (FNG) increased and the number of non-flower nodes (NFN) in a non-flower node group (NFNG) decreased by the shortening of day-length, though no significant change was observed in the length of cyclic appearance of FNG and NFNG along a stem. In consequence, the number of FN per unit number of nodes on a rosette increased with the shortening of day-length. Moreover, the growth of leaves was suppressed and the size of a leaf become smaller. In a rosette, although the number of leaves increased, the size of rosette tended to become smaller. Similaly, the size of flower buds or flowers immediately before or after flowering, respectively, was decreased by short-day treatment. The results obtained in the present study suggest that development of fruit may be suppressed by excessive short-day conditions.
