Of Environmental Factors On Photosynthesis

In this thesis, the influence of some factors, such as temperature, water potential in soil, light intensity and the different levels of N, P, K, on such parameters as photosynthetic capacity, carboxylation efficiency, apparent quantum yield of photosynthesis, photorespiration, photochemistry efficiency, stomalal limitation and chlorophyll content in leaves of field grown and pot-cultured Ginkgo seedlings were examined and analyzed systematically. Its aim is to probe into the inherent relationship between different environmental factors and the photosynthetic characteristics so as to direct how to achieve high yield and quality of Ginkgo production . The main conclusions are as follows :1.The photoinhibition and the decline of net photosynthetic rate at midday were lessened remarkably by means of shading ,which was due to the cross stress of high temperature, high light intensity and large VPD.2.1n various light intensity , more reasonable allocation of light energy absorbed by Ginkgo leaves could be carried out by regulation of photochemistry efficiency .3.The optimal temperature for photosynthesis of Ginkgo leaves depends on season and water potential in soil.4.Also, the optimal temperature range for photosynthesis of Ginkgo leaves was related to the water potential in soil.5.Net photosynthesis rate, carboxylation efficiency and photochemistry efficiency decreasd under each stress of high temperature, high light intensity and large VPD and went down more sharply under the cross stress of them .6.Ginkgo had a very strong tolerance capacity to drought, which was duo to its lower stomatal conductance.7.Sufficient water supply could not only improve net photosynthesis rate of Ginkgo ,but also extend the time of efficient photosynthesis of gingkgo.8.Dark reaction of photosynthetic system of Ginkgo leaves was more sensitive to the stress of drought than light action.9.Lack or excess of each of N, P, K could lead to the decrease'of photosynthetic capacity and activeness of photosynthetic organ. However, they were more sensitive to N than P and .10.Morderate supply of N, P and K could lead to more lower ratio of pholorcspiriitinn to mass photosynthetic rate of Ginkgo leaves, and also could enhance its water use efficiency...