Study On Genetic Adaptation Mechanism For Low Phosphorus Stress And Phosphorus Efficiency In Pinus Massoniana Lamb.

Total phosphorus(P)is rich in the soil but its available P very scarce. It is very important to develop special tree genotypes to exploit the P in the soil efficiently, which can solve the available P "genetic deficiency". In this paper, liquid and soil culture experiments at 3 P levels were conducted to illustrate the differences including growth, P uptake and its kinetic parameters, root exudates, acid phosphatase activity, morphology of root and P efficiency among five provenances of masson pine which showed different responses to P supply, the differences also were studied in nine families. The genetic adaptation mechanism for low P stress and genetics of P efficiency were expatiated primarily, and differential parameters for P efficiency were determinated in the paper. In the end of it, some advice and expectation about tree nutrition genetic researches were brought forward.The conclusions indicated that, with P supply in the medium rising, the growth (including height, width, dry substance), total P uptake, Km and Cmin rised while Imax and distribution of dry substance in the root decreased in all provenances tested. All these change patterns varied with provenances and families, among which Chun'an of Zhejiang, Chongyi of Jiangxi, Cenxi of Guangxi and Family 3 and 8 showed stronger sensitivity to P supply, they gained much more plus when given more P and were thought to be excellent genotypes with high P efficiency. Wuping of Fujian, Xinyi of Guangdong, Family 5, 6 and 7 showed less sensitivity.Low P stress intensively stimulate the release of APase by root of mason seedlings and increased obviously APase activity in seedling root and leaf. Besides, more amount of organic acid such as oxalic acid, acetic acid and malic acid, and little amount of amino acid were detected with P starvation aggravation. Under low P adversity, Wuping of Fujian and Xinyi of Guangdong had relatively greater P uptake, APase activity and Imax, smaller Km and Cmin, their amount of organic acids were also greater than the others. With a view to theirgreater height and biomass accumulation, the two provenances were considered to be splendid genotypes with stronger tolerance to low P. Also, Family 5, 6 and 7 showed greater growth than other genotypes and had excellent adaption to P starvation. Study on morphology of root and distribution of dry substance showed that, under low P circumstances, there existed observable differences among provenances and families tested in the quantity and length of sideroot, root volume and total fibre, but no distinct differences in the length of taproot. Height, width and biomass all showed positive markedly relation to root volume, the length and quantity of sideroot, root cap rate and total fibres, but no relation to the length of taproot and root cap rate.In view of the relation between growth and differential parameters such as root morphology and P efficiency, under low P environment, some indexes such as P uptake and utilize efficiency, root volume, the length and quantity of sideroot, fibre density, total quantity of fibre, APase activity, excreted organic acid, and P uptake kinetic parameters can illuminate the growth of masson pine under P deficiency, and can be treated as differential parameters for P efficiency.The genetic research on P efficiency indicated that there were great family heritability in differential parameters such as P efficiency, uptake efficiency, utilization efficiency, height, width and biomass (Hp=0.6533~0.9331), which indicated that cultivate and develop forest plantation by selecting excellent genotypes with great tolerance to low P or high P efficiency is efficient and feasible.