The Fitness Analysis Of Hybrids And Parental Species Of H.goniocarpa Hybrid Zone

Natural hybridization can be viewed as an important factor in evolution. Naturalhybridization not only provide genetic basis for plant to resist harmful environmentand occupy new habitat but also is a way to make speciation. The study on the relativefitness of hybrids and their parents has a important significance, which can give us agood way to predict the hybrid fortune and to understand the maintenance mechanismof hybrid zone. In the present thesis, the experiment studies on the fitness of parentalplants H.rhamnoides subsp. sinensis and H.neurocarpa and their hybrid plantsH.goniocarpa were conducted through the comparision of seed germination,antioxidase activity and photosynthesis characters. The results are summarized asfollows:(1) The seed weight of H.goniocarpa is intermediate of its parental plants. Thepercentage of fully developed seeds of H.goniocarpa is lower than that ofH.rhamnoides subsp. sinensis and H.neurocarpa. The germination percentage ofH.goniocarpa is lower than H.rhamnoides subsp. sinensis and H．neurocarpa underlower temperature treatment (15℃, 20℃). The GV value of H.goniocarpa is lowerthan that of H.neurocarpa. The length of the radicle and hypocotyl on the final day ofH.neurocarpa is lower than that of H.rhamnoides subsp. sinensis at 15℃,and issignificantly lower than that of H.neurocarpa at 20℃.These results show thatH.goniocarpa does not have the hybrid heterosis and does not exceed its parentsduring seed period.(2) In the hybrid zone of Qilian gongbaiwan, Qinghai, the content of MDA ofH.goniocarpa and H.neurocarpa are significanly lower than H.rhamnoides subsp.sinensis.The SOD activities is no significant difference between the hybrid and itsprantal plants.The activities of CAT of H.goniocarpa is the highest value and issignificant high than that of H.neurocarpa.There is no significant difference betweenactivities of CAT of H.goniocarpa and that of H.neurocarpa. There also are nosignificant difference between hybrid and its prantal plants in content of solubleprotein.The content of MDA may indicate that H.goniocarpa does not suffer moreserious stress.The antioxidase activity coordination show H.goniocarpa and its two parents all have the ability to adapt the environment.(3) In the sample land, H.goniocarpa and its two parents have no"middaydepression", which indicate the H.goniocarpa and its two parents have the specificphotosynthesis character to adapt high altitude environment. The Tran and CONDraise with the altitude enhance, which show H.goniocarpa and its two parents havepositive response of the altitude change. H.goniocarpa has the highest photosynthesiscapability and WUE efficiency at lower altitude and the lowest photosynthesiscapability and WUE efficiency at higer altitude, and Pn is not change with altitude. Insome degree, H.goniocarpa can compete light and water successfully with its twoparents, but H.goniocarpa may more fit at lower altitude region.(4) To sum up, the fitness H.goniocarpa does not exceed its two parents. Thismay be the reason of the small quantity of H.goniocarpa in the hybrid zone.