Wong, Min May (2012) The reproductive biology and cytotoxic activity of Persicaria chinensis (L.) H. gross var. chinensis (polygonaceae) / Wong Min May. Masters thesis, University of Malaya.
Abstract
Persicaria chinensis var. chinensis is a native variety in Malaysia and found in the tropics growing in lowland and lower montane forests. Growth habit and morphological differences were observed between the highland and lowland varieties. The anthesis of the highland wild population was at 0600–0730 hours whereas that of the lowland variety was at 0745–0930 hours. The anther is tetrasporangiate and the wall development conforms to the Monocotyledonous type. Cytokinesis in the microspore mother cells is simultaneous forming tetrahedral and decussate tetrads in the highland variety and mostly tetrahedral tetrads in the lowland variety. The mature pollen grains are shed at the three-cell stage. The ovule is orthotropous, bitegmic and crassinucellate and the micropyle is formed by both the outer and inner integuments. The development of the embryo sac conforms to the monosporic Polygonum type. An occurrence of twin eggs within an ovule was observed in the lowland variety. In the highland variety, the development of the endosperm is ab initio Nuclear type. The highland variety is heterostylous; pin flowers have taller style, shorter filaments, less thick and less wide stigma than the thrum flower. The number of pollen grains in a pin flower is higher than that in a thrum flower. The pollen grains of the thrum flowers are bigger than those of the pin flowers. The pin and thrum pollen grains are 3-colpate, medium-sized, suboblate to oblate and have reticulate exine with thick, narrow muri and free clavae in the deep lumina. The lowland variety is observed to have only thrum flower. They have shorter style, longer filaments, thicker and wider stigma than those of the highland thrum flowers. The pollen grains of the lowland variety are bigger than those of the highland thrum flowers. Their lumina were less wide and the muri were thicker, less narrow and shorterthan those of the highland thrum pollen with free clavae. In the highland variety, the optimum sucrose and PEG concentration for pollen germination was 15% and 30% respectively. Bursting of pollen grain occurred in the medium without PEG. Pollen grains reached maximum germination (50%) in the modified medium with an average pollen tube length of 140 µm. The highland variety of P. chinensis var. chinensis was self-compatible. Open pollination produced three times more fruits than self pollination and they are crosscompatible and show outbreeding. The pollen-ovule ratio suggested the breeding system was facultative xenogamy. The most common insect visitors are from the Order of Hymenoptera. Seed germination is epigeal showing 77% viability. The average percentage of germination for the fresh seeds was 47% in the natural highland environment and 34% in the lowland laboratory environment. In Malaysia, P. chinensis var. chinensis has been used traditionally as one of the main ingredients in Chinese traditional medicine to treat various lung ailments including cancer. The in vitro neutral red cytotoxicity assay was successfully applied to screen the cytotoxic activity against 18 crude methanol, dichloromethane and water extracts from the highland and lowland varieties of P. chinensis var. chinensis derived from the leaf, stem and whole plant. Overall results showed that the methanol extracts from the leaf samples of the highland and lowland varieties possessed greater cytotoxicity effect against cancer cell lines. Two active extracts obtained from the methanol leaf extracts of the highland and lowland varieties were more effective in suppressing the expression of CaSki and SKOV-3 cells. The dichloromethane extract from the stem sample of the highland variety also showed significant cytotoxic effect against HT-29 cells. Since both varieties showed signs of the selectivity for CaSki, SKOV-3 and HT-29 cells, these findings suggest that P. chinensis var. chinensisshould be further researched to isolate and identify the active compound(s) from the active extracts which demonstrated significant cytotoxic activities.
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