Abstract
The relationship between the canopy formation and yield performance of Trapa bispinosa Roxb. in paddy fields was investigated under the following six conditions: vinyl house culture (VH); shade culture (SC); and open field culture (OP); with and without fertilizer (F). The speed of the canopy formation varied with treatments, and the formation of the complete canopy of emersed leaves was hastened in the following order :VH+F>VH>OP+F>OP>SC+F>SC. The number of productive rosettes tended to increase corresponding to the earliness of the maximum rosette number stage. Furthermore, the variation at about 20 days was observed during the first flowering time to correspond to that during the maximum rosette number stage. Yield varied from 506 to 1190 gm-2 and increased under the condition of early canopy formation. The cumulative number of flowers per rosette ceased to increase at the same time, regardless of the timing of the first flowering, which showed a significant correlation with the timing of the first flowering. Also, high correlations were seen between the maximum rosette number stage and the first flowering, and between the cumulative number of flowers and the number of valuable fruits per rosette. Therefore, it can be proved that the increase in number of valuable fruits per rosette depends on the increase in the cumulative number of flowers per rosette owing to a prolonged flowering period, which arises from the promotion in canopy formation and commencement of flowering.
