Sexual Reproduction And Adaptability Of Tamarix Chinensis (Tamaricaceae) In Yellow River Delta

Yellow River Delta, as a rapid increasing landmass in the world, is predominated by arborescent shrub, Tamarix chinensis. Succeeding in sexual reproduction is close relative to the surviving and expanding of tamarisk's population, thereby we studied the species on sexual reproductive process and relative ecology for the first time, and try to find the inherent adaptation to its wide distribution in this virgin land. By means of orientational observation in the field, flowering phenology, flowering dynamic, kinds of pollinators and their behavior and visiting frequency were observed and the breeding system, pollen-ovule ratio (P/O) and pollen viability were determined. The results showed that T. chinensis was self-compatible requiring pollinators. Syrphid flies (Syrphus) were the most common visitors. The duration of single flower of this plant lasted only one day, the P/O was 390.9 + 81.0. The population had a flowering period of several months (from May to September), which produced a large amount of seeds that would germinate and form a large area of Tamarix shrub. Using traditional paraffin wax section, we observed the embryology of T. chinensis in detail. The process of megasporogenesis, microsporogenesis and the development of female and male gametophyte of this plant made it successful to produce developed embryo sac, which is of Fritillaria type, and fertile pollen grains. Both of them matured on the first day of flowering. Fertilization was initiated on the second day and the duration was very short. The zygote underwent mitosis immediately and had hardly dormancy. In addition, zygote mitosis was initiated early than primary endosperm nucleus and its nutrition of development was provided mainly by suspensor. Developmental duration of embryo was approximately 15 days. Germinating characteristics and response to different concentration of NaCl and seawater were studied in different treatments. The main results are summarized as follows: Seeds of T. chinensis have a shorter life and can survive only 14 to 40 days in room temperature (27~29°C). The seed quality varies in different mature time. Its germination process differs from general plant seed's, and the root hairs produced early comparing to the hypocotyls elongation. In addition, Tamarisk has a high resistance to single salt toxic and high concentration of seawater, which can make its seeds naturally germinate in 0.2mol/L NaCl or 100% seawater. In terms of sexual reproduction and ecology, T. chinensis has some inherent adaptation in the full process of reproduction, including flowering, pollination, fertilization, development of embryo and endosperm and the germination of seed, which made it predominated in the Yellow River Delta. This study provides a platform for its further study of reproductive biology, and also given a theoretical guide to the utilization and conservation of T chinensis.