| This research takes annual potted seedlings of Bischofia javanica as the experimental material to observe and measure their growth, physiological index and photosynthetic indicators after they are in shadow for six months according to four light gradients, i.e.100%NS (natural sunshine) and41.3%NS,14.6%NS and3.6%NS. It also analyzes their shade-tolerance mechanism and stain resistance ability based on the the correlation analysis, principal component analysis, comprehensive evaluation of membership function value method and plasticity analysis. By doing so, the author attempts to provide certain theoretical basis for the plant configuration and landscaping and the alike. What this research reveals are as follows:1) There were diverse influences on growth index in the four light indicators of Bischofia javanica seedlings. Along with the rising of the shade degree, the seedling height growth, diameter growth, leaf area, fresh weight of under ground portion, fresh, whole plant fresh weight of above ground and underground part of the dry weight, dry weight above ground, whole plant dry weight of Bischofia javanica seedlings all show a trend of first increasing and then declining, and arrive at the peak in41.3%NS; while the root volume, root total length, total surface area, total root number, total root average diameter all presents a decreasing trend.2) There were diverse influences on physiological indexes in the four light indicators of Bischofia javanica seedlings. Along with the rising of the shade degree, the content of chlorophyll, content of chlorophyll a, content of chlorophyll b, soluble sugar content first increase and then decrease. Cell membrane permeability, the content of Malondialdehyde (MDA), the content of proline content and the activity of CAT first decrease and then increase, the minimum values appear in41.3%NS; Soluble protein and the activity of SOD show a declining trend.3) There were diverse influences on photosynthesis indexes in the four light indicators of Bischofia javanica seedlings. By measuring photo-response curve of Bischofia javanica seedlings under diverse light conditions, the author finds that as shadow degree rises, the light compensation point, light saturation point, maximum net photosynthetic rate, dark respiration rate decrease, while the apparent photosynthetic quantum yield increases. By measuring the daily changes of net photosynthetic rate, stomatal conductance, intercellular CO2concentration and transpiration rate of Bischofia javanica seedlings under diverse light conditions, the author finds that four light processing type net photosynthetic rates are bimodal curve and achieve the first peak at12:00, moreover,100%NS treatment reaches the second peak at16:00, the other three ones at17:00. The net photosynthetic rate in100%NS is best, while the highest average daily net photosynthetic rate occurs in41.3%NS light, The change of intercellular CO2concentration is opposite to its net photosynthetic rate. The transpiration rate and stomatal conductance daily vary in accordance with the net photosynthetic rate in100%NS and41.3%NS light, while the transpiration rate and stomatal conductance are of unimodal curve in14.6%NS and3.6%NS light, and both arrive at the peak at14:00.4) The comprehensive analysis shows that the daily average net photosynthetic rate and growth indexes including underground part of fresh weight are significantly or extremely significantly correlated, so are the maximum net photosynthetic rate and physiological indexes including soluble protein. The first principal component of Bischofia javanica seedlings comprise mainly underground part of the index, dry weight, root soluble protein, free proline, SOD, MDA, relative conductivity, the chlorophyll content and the maximum net photosynthetic rate. The second principal component includes chiefly underground part of the fresh weight, fresh weight and dry weight above ground, whole plant fresh weight and dry weight of seedling, height growth, diameter growth, single leaf area of seeding and soluble sugar, the CAT and the daily average net photosynthetic rate. Bischofia javanica seedlings’s membership function value of is0.472, which makes this plant a specie of moderate shade tree. Their average value of growth plasticity index is0.504, average value of physiological plasticity index is0.664, average value of photosynthetic indicators plasticity is0.570, which ensure that Bischofia javanica seedlings have a high potential ability to adapt to the shade environment.In summary, the annual Bischofia javanica seedlings have a strong tolerance of shade which is naturally propitious to their growth. |
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