Studies on matter production of rape plants. IX The number of seeds per pod and seed weight as influenced by pod and seed positions on the plant.

Abstract

Using soil-cultured rape plants (Brassica napus L., cv. Norin No.16) grown in pots, intra-branch and intra-inflorescence variations in the number of seeds per pod and seed weight, and also intra-pod variations in seed weight and seed set percentage on a plancenta were investigated. The results are summarized as follows : 1. Compared on kinds of branches, mean number of seeds per pod was higher in pods on the inflorescences of main stem and of primary branches than in those on the inflorescences of secondary branches. Mean seed weight was highest in the inflorcscence of main stem, decreasing in the order of the inflorescences of primary and secondary branches (Table 1). 2. No differences in mean number of seeds per pod among the inflorescences of primary branches in any position on the main stem were detected. But, the higher primary branch position on the main stem counted upward from the base, the larger mean seed weight on the inflorescences of primary branches (Fig. 1). 3. No relationships between the number of seeds per pod and pod position on the inflorescence of each kind of branch were detected (Figs. 2, 3 and 4). On the other hand, the higher pod positions on the inflorescences of main stem, of primary branches and of secondary branches counted upward from the base, the less mean seed weights (Figs. 5, 6 and 7). 4. Seeds located near the base in a chamber had lower seed weight, but seeds located at other seed positions in a chamber had almost similar weight in a pod on the inflorescence of main stem. In pods on the inflorescences of primary and secondary braches, it seemed that seed weight increased according to the change of seed position from the base to the middle in a chamber and was nearly constant at seed positions after the middle (Fig. 8). 5. Seed set percentages on a plancenta were low at the positions near the base and the top in a pod on the inflorescence of main stem. In pods on the inflorescences of primary and secondary branches, it seemed that seed set percentage on a plancenta increased according to the change of seed position from the base to near the top in a chamber though it decreased slightly at the top in a chamber (Fig. 8)