Research On Machilus Pauhoi Seed Ings’ Growth&Physiology Characteristics At Different Shading Levels

The8month seedlings of Machilus pauhoi were placed in100%,31.5%,11.3%&4.7%natural sunshine environment especially. Their growth, physiological and photosynthetic index were observed,measured and analyzed after half a year, meanwhile conducting the analysis of principal component and plasticity, carrying on comprehensive evaluation of fuzzy membership to comprehend the intensity demand of Machilus pauhoi seedlings, so as to provide certain theoretical basis and technical support for seedling cultivation&afforestation. The experimental results show that:(1) The growth of Machilus pauhoi seedlings was different at different shading intensity levels. With the increase of the shading intensity, its ground diameter growth,height growth,l-eaf area, fresh and dry weight of the whole plant, fresh and dry weight of stems&leaves had a trend of increase first and then decrease, and reached the maximum value in31.5%NS; fresh and dry weight, the Tips, Length, Surface Area, Root volume, Average Diameter of root had a trend of continuous reduction.(2) The physiological condition of Machilus pauhoi seedlings was different at different shading intensity levels. Along with the gradual increase of shading degree, the content of chlorophyll a, chlorophyll b and total chlorophyll increased continuously, while chlorophyll a/b decreased. With the gradual increase of shading degree, the content of malondialdehyde, cell membrane permeability and free proline had the trend of decrease first and then increase, and detailed results was100%NS>4.7%NS>11.3%NS>31.5%NS.While catalase activity had the trend of first increase and then decrease, and detailed results was31.5%NS>11.3%NS>4.7%NS>100%NS.(3) And the diurnal variation of photosynthesis have different response curve of Machil-us pauhoi seedlings in different intensity of light shade environment.Light compensation point, light saturation point, maximum net photosynthetic rate, dark respiration rate decreased with the increase of shading degree,while the apparent quantum yield had the trend of increase first and then decrease. Ascertain by measuring photosynthetic diurnal variations of Machilus pauhoi seedlings at different shading levels, the diurnal variation of net photosynth-etic rate, stomatal conductance, transpiration rate showed that their variation law were almost the same, while the diurnal change of intercellular CO2concentration was opposite. The com- parison results of average net photosynthetic rate was31.5%NS>100%NS>11.3%NS>4.7%NS, while the comparison results of intercellular CO? concentration was4.7%NS>11.3%NS>100%NS>31.5%NS. Average stomatal conductance and transpiration rate performed simi-lar whose detail results were100%NS>31.5%NS>11.3%NS>4.7%NS.(4)Comprehensive analysis showed that the first principal component of Machilus pauh-oi seedlings mainly included the height growth, diameter growth; the Tips, Length, Surface Area, Root volume, Average Diameter of root; fresh and dry weight of stems&leaves, root and whole plant; the content of chlorophyll a, chlorophyll b, total chlorophyll; the average net photosynthetic rate; the second principal component mainly comprises average area of a sing-le leaf blade; the content of MDA and praline; the activity of catalase; the relative conducti-vity. The membership function value of Machilus pauhoi seedlings was0.520, belonging to moderate shade tolerance tree. Plasticity analysis showed that the growth indexes of plasticity is largest which concrete index is0.857, physiological plasticity is0.604, photosynthesis plasticity of0.559.Machilus pauhoi seedlings have moderate shade tolerance according above conclusions. In this experiment, Machilus pauhoi seedlings’growth&physiological characteristics show best performance under31.5%NS shading environment.