Study On Seedling Plasticity In Xanthoceras Sorbifolium Bunge Under Light Stess

In the study, the Xanthoceras sorbifolium Bunge seedling was chosen as the main object, the growth characteristics (morphological traits and quality traits), distribution characteristics and photosynthetic characteristics of seedling in Xanthoceras sorbifolium Bunge responding to different light intensities under light stress and natural light were systematically studiedby improving the past questions of few dimmer gradient. The dimmer experiments were conducted under seven gradients of light treatment (natural light, shading 20%, shading 35%, shading 50% shading 75%, shading 80%, shading 95%) to study the responds to light heterogeneity of Xanthoceras sorbifolium Bunge seedling by ANOVA, PCA, regression analysis, correlation analysis path analysis and so on, and synthetical evaluation was discussed with phenotypic plasticity to provide scientific basis for the breeding of Xanthoceras sorbifolium Bunge. The results showed that:(1)LA, H, MLL, MLM, MLN of Xanthoceras sorbifolium Bunge seedling generally increased first and then decreased with the decrease of light intensity, showing significant differences. Light stress influenced the accumulation and distribution of biomass, the biomass accumulation of seedling in the low light treatment was less than that in natural light, which was especially obvious under weak light stress, improved the ratio of AB and BB by adding SM and LM, reducing RM.(2) The principal component was analyzed to study the growth characteristics and distribution characteristics of Xanthoceras sorbifolium Bunge seedling with Canoco and SPSS statistics softwares. The results showed that PCA datas obtained from Canoco was better than that from SPSS. Furthermore, the first two ordination axes of PCA were chosen as the dependent variable and the plant traits as the independent variable to carry out the multiple stepwise regressions. The regression equation was used to evaluate plasticity characteristics of plants, which also provided a new calculation method for characteristics integration.(3)The Pn, PAR, Cond, Tr and other indicators of Xanthoceras sorbifolium Bunge seedling were significantly effected under different light. The Pn of Xanthoceras sorbifolium Bunge under more than 50% of the light-shielding showed no midday depression and the shading promoted elimination of midday depression; PAR decreased with the decrease of light intensity; Tr of seedlings under more than 50% light-shielding first increased and then decreased. Cond of seedlings under natural light, shading 20%,80% and 95% first decreased, then increased and finally decreased, while the Cond of seedling under shading 35%,50% and 75% only gradually reduced. Changes of PAR in response to Pn remained roughly the same under different light intensities, all generally increased to the maximum value then and remained unchanged.(4) The LM, SM, RD, MLL, RL of Xanthoceras sorbifolium Bunge seedling had significant effect on Pn by correlation analysis and path analysis between growth characteristics. The PL and SM were the major factors to influence the Pn of seedling under natural light, shading 20%,35%; The SM, MLL and MLN were the major factors to influence the Pn of seedling under shading 50%,75%; The RD and LN were the major factors for the Pn of seedling under shading 80%,95%.