The effect of floret size and its maturation on seed size variation within infructescences in Japanese wing nut (Pterocarya rhoifolia)

Abstract

Japanese wing nut (Pterocarya rhoifolia) showed about eighteen times variation in seed mass within a species. In this study, we have especially focused on the proximal factors generating the seed size variation within an infructescence. Seeds at proximal end of infructescence were generally greater in mass than those of distal end. Since flowering time among florets at different positions on inflorescence (proximal, intermediate, distal end, respectively) did not differ on another, it could be concluded that flowering phenology did not affect seed size variation. However, sizes of florets were significantly larger at proximal end than those of distal end. Moreover, flower-removal treatment resulted in enhancing the size of intermediate and distal seeds derived from remaining florets. But the sizes of seeds at proximal end did not differ from control. Therefore, it did not reveal that whether the resource competition among the seeds on an inflorescence for maternal resources was the sources of seed size variation. This study showed that the sources of seed size variation in Japanese wing nut are the initial floret size among different position on the inflorescence.