Growth and Yield Performance of the Water Chestnut (Trapa bispinosa Roxb.). III. Developmental process of fruit.

Abstract

Development of fruits of Trapa bispinosa Roxb. cultivated in paddy fields was investigated from the viewpoint of nodal succession along a stem and of flowering time, and variability of valuable fruit weight was analyzed. Differentiation of flower buds, flowering, and growth of fruits proceeded together with increase in the number of leaves on the stem. The deviation in the phenomenon was small among the stems that flowered in August. By the comparison of the final weight of fruits whose flowering time differed, the existence of a time-limit in flowering for obtaining valuable fruits was noticed, and the effective flowering period was assumed to be from the first flowering time to mid-September. Furthermore, by the change of the ratio of valuable fruit number per flowers bloomed (RVNF), the period of flowering was classified into three stages : i. e. early (from first flowering time to late August), when the RVNF is high and stable ; middle (from beginning to mid-September), when the RVNF decreases ; and late flowering period (after mid -September), when the time of effective flowering reaches its limit and the RVNF becomes zero. In the early flowering stage, the variation in the final size and amount of fruits was small irrespective of the flowering time and the kind of stems. Also, a considerable percentage in total number of valuable fruits seemed to consist of the fruits whose formation had started at the early flowering stage, since the stage is much longer than the middle flowering stage. Consequently, the above-mentioned phenomenon is thought to be the factor contributing to the small variability in the size and amount of valuable fruits, stabilizing their average weight.