A Comparative Morphology of Dorsal Vascullar Bundles, Nucellar Projections and Transfer Cells in Gramineous Caryopses

Abstract

Dorsal vascular bundles, nucellar projections and transfer cells in 62 species of the gramineous caryopses were examined by light microscopc. These results were then considered in relation to the grass systematics. Considering a halflength of thc caryopsis, small vascular bundles and short nucellar projections were observed in the plants belonging to Panicoideae and Eragrostoideae, small vascular bundles with short nucellar projections and large vascular bundles with long nucellar projections were observed in Festucoideae. Studies conducted on the face view of hila (KINGES l961) show some correlation (present investigation) between the shape of the hilum and the relative size of vascular bundle and the length of nucellar projection. It was seen that the plants having small vascular bundles with short nucellar projections mostly showed pointed or ellipsoidal hilum, whereas those having large vascular bundles and long nucellar projections always showed linear hilum. Hence seeing the table of KINGES, giving different shapes of hila, one can predict the size and type of different tissues where such studies have not been performed. In the present study, looking at the different shapes of hila as indicated by KINGES, the size of vascular bundle and the type of nucellar projection has suggested in subfamilies such as Panicoideae, Eragrostoideae and Festucoideae. Preliminary investigations conducted by us on Bambusoidae and Oryzoideae also support this view, where large vascular bundles with long nucellar projections have been found. Also considering TATEOKA'S phylogenic scheme on Gramineae, it seems quite possible that small vascular bundles and short nucellar projections evolved from large vascular bundles and long nucellar projections during the course of evolution. Appearance of transfer cells in the peripheral endosperm at the basal region of caryopsis was virtually restricted to the plants of Panicoideae. This result suggests that once these cells evolved, they perpetuated during the subsequent evolution of the subfamily. From the distinct differences in the cell wall ingrowth between Andropogoneae and Paniceae, it has been observed that Andropogoneae is characterized by the presence of more highly developed transfer cells than Paniceae.