여뀌科 異型蘂植物의 稔性 및 發生學的 硏究

Studies on the Fertilities and Embryological Differences in the Heterostylous Species of Polygonaceae

Although most of the plants belonging to the Polygonum family are homostyled, three species, Persicaria, japonica, Fagopyrum esculentum, and Persicaria senticosa, have dimorphic heterostylous floral organs. Examining the morphological, ecological and physiological traits of these heterostylous plants, Harn once suggested that in the differentiation of sex from hermaphrodity to dioecism in the sporophyte of angiosperms some species have taken the course of differentiation from homostylous flowers to the heterostylism. Present experiments were attempted in order to confirm the above-mentioned hypothesis by examining further the pollen tube growth, fertility, micro-and megaspo-rogenesis, gametophyte formation, development of egg-apparatus, and changes of parietal tissue of anthers in the dimorphic flowers of these species. In the illegitimate unions in both long-and short-styled flowers of P. japonica and F. esculentum, pollen tubes were arrested at below-stigma or at mid-style, while in P. senticosa they reached the ovary without any difficulties. In legitimate pollinations pollen tube growth was most rapid in P. senticosa, slowest in P. japonica, and intermidiate in F. esculentum. L-style pollens as well as S-style’s of P. senticosa and F. esculentum were perfect and fertile while L-anthers of P. japonica were somewhat less developed and had fewer pollens, of which about 80 % were empty and sterile. As morphological and functional differentiation between L - and S - style anthers progressed so extremely that P. japonica behaved in every respect like dioecious plant. There were no changes in fertility when examined at different stages of flowering season in the three species. Generally the L- floweres, however, had better fertility. In the L-style of P. japonica, mega-sporogenesis, megagametophyte formation, and development of egg-apparatus proceeded regularly, but in S-style irregularites prevailed probably due to the abnormal development of megaspore mother cells and irregular mega-sporogenesis. In the development of micro-sporogenesis and micro-gametogenesis, however, the reversional phenomena were the rules. In F. esculentum micro-and mega-sporogenesis, gametophyte formation, egg-apparatus, and changes of anther wall tissue were normal both in L-and S-style individuals. In P. senticosa, also, no difference was observed between L-and S-style in their sporogenesis and gametogenesis. P. japonica and P. senticosa had bitegumic orthotropous ovules, but F. esculentum was found to have unitegumic orthotropous ovule. In taxonomy P. japonica is regarded as dioecious plant. Present experiments including embryological studies, however, have revealed that this species is of the typical dimorphic plant along with the other two heterostylous Polygonum species. All the evidences obtained from the embryological studies as well as the results based on the pollen tube growth and fertility of the three heterostylous Polygonum species showed that P. japonica had wide differences between the two styles indicative of dioecism, P. senticosa seldom changed except the style and filament length, and F. esculentum was just intermediate between the two species.