Research On The Catalpa Bungei In Seedlings About Genetic Variation Of Clonal Nitrogen Nutrition Efficiency And The Selection Of High Efficiency Clones

This paper viaed low and high nitrogen treatments to research genetic variation model of clonal growth,photosynthetic and nitrogen absorption characters, differences of clonal nitrogen efficiency,taking biomass of stems as standard deficiency to construct rapid selection index system of fast-growing,high deficiency Catalpa bungei excellent clones, in order to provide theoretical basis for Catalpa bungei nutrition genetic study and excellent clonal rapid selection research,and screening clones which suit for extended in different nitrogen environment from all tested clones.Main research results of this paper are several points below:(1) Variation of growth , photosynthetic and nitrogen absorption characters are different under two nitrogen treatments.Clonal growth all exhibit great difference under two nitrogen treatments.After increased nitrogen content of soil ,net increase of seedling height, net increase of basal stem, biomass of per plant, net photosynthetic rate, light energy conversion rate and nitrogen content of each organ all exhibited increasing trend,but nitrate reductase exhibited decreased trend. net increase of seedling height, net photosynthetic rate,total chlorophyll, nitrogen content of leaf, nitrogen content of stem, biomass of per plant, ratio of above-ground part and underground part all had great variation degree among clonesunder under low nitrogen treatments,but transpiration rate, nitrate reductase and root activity had great variation degree among clones under high nitrogen treatments. Repeatability of net increase of seedling height, net increase of basal stem, biomass of per plant, ratio of above-ground part and underground part, net photosynthetic rate, transpiration rate, nitrate reductase all reached higher than 0.7 under two nitrogen treatments, showing that they were under strength genetic control,however repeatability of total chlorophyll, light energy conversion rate ,root activity,and nitrogen content of each organ changed greatly under different nitrogen treatments,showing that they were effected by greater environmental factors.(2) Tolerance of different characters have different adaptation under low nitrogen stress,variation of nitrogen tolerance coefficient in every character of each clone are larger.According to size of variation degree to sort :root activity(CV=43.0% )>NR(CV=32.6%)>transpiration rate(CV=27.1%)>content of chlorophyll a(CV=16.1%)>total chlorophyll(CV=15.7%)=content of chlorophyll b(CV=15.7%)>net increase of seedling heigh(tCV=15.3%)>net photosynthetic rate(CV=14.2%)>content of carotenoid(CV=14.1%)>light energy conversion rate(CV=0.7%). (3) Nitrogen efficiency variation of clones under two nitrogen teatments are different.Nitrogen absorption efficiency mean of clones under low and high nitrogen teatments are 0.035 and 0.106 respectively, amplitude are 0.026～0.050 and 0.085～0.122 respectively,CV are 18.5% and 11.1%;nitrogen utilization efficiency mean are 119.714 and 57.038, amplitude are 104.773～130.700 and 53.882～61.622 respectively,CV are 6.4% and 4.6%;nitrogen economic utilization efficiency mean are 31.189 and 21.981 respectively, amplitude are 26.193～37.249 and 19.417～28.056 respectively,CV are 11.6% and 10.9%;leaf nitrogen productivity mean of leaves are 78.573和38.883 respectively, amplitude are 61.196～92.712 and 31.562～50.736 respectively,CV are 13.4%和15.09%. So variation of nitrogen absorption efficiency, nitrogen economic utilization efficiency, leaf nitrogen productivity of leaves among clones are higher,variation degree under different nitrogen teatment are different.(4) Because Catalpa bungei is timber tree , the size of biomass of stems influence high low of timber volume directly.Viaing correlation analysis about biomass of stems,absorption efficiency of nitrogen, economic use efficiency of nitrogen and other growth, phtosynthenic and nitrogen absorption characters,screening that net increase of seedling height, net photosynthetic rate, light energy conversion rate , nitrogen content of stems all can as high yield Catalpa bungei clonal selection indexes.(5) Classify all tested clones by making biomass of stem as main factor. Stable and efficient clones (eurytopic type), including 2-7 and 2-8, can extend and afforest in environment of sufficient or barren nitrogen content simultaneously; 9-1和2-8 both are stenobiontic type of clones, which suit for planting in environment of sufficient nitrogen content and deficient nitrogen content respectively.