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Physiological Study on the Shade and Drought Tolerance of Polygonum Capitatum Buch.-Ham. Ex D.Don

Author: WuZongPing
Tutor: LiLing
School: Southwestern University
Course: Ornamental Plants and Horticulture
Keywords: Polygonum capitatum Buch. -Ham. ex D.Don Shade-tolerance Drought-tolerance
CLC: S567.239
Type: Master's thesis
Year: 2010
Downloads: 113
Quote: 2
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Abstract

Polygonum capitatum Buch. -Ham. ex D.Don is a kind of perennial wild medicinal plants widely distributed in China, it is of high economic and ornamental value. By taking the local P. capitatum form Junyun mountain in Chongqing Beibei selected as the research material, the change of morphology, appearance performance, the physiological and biological index of the plant under different shade and drought stress were observed and measured. The results are as follows:Shading affected on the local environment which P. capitatum were planted. It increased air relative humidity but decreased light intensity, air temperature and land temperature.Compared with those under 100% of sunlight, the plants which were treated by shading indicated that leaf length, leaf width, leaf areas and internode length were increased and the leaf got thinner, the thickness ratio of palisade and sponge tissue declined. But leaf areas, length and width were decreased relatively in 8.8% of full sunlight, and the cells of palisade tissue were loose arrangement and unconspicuous.The effect of shading was significant on the performance of photosynthetic pigment of P. capitatum, with the contents of chlorophyll and carotene increasing while the ratio of Chla/Chlb decreasing.Soluble sugar content, soluble protein content and proline content of P. capitatum were decreased gradually while the leaf water content of P. capitatum was increased significantly under shading. According to the research on the shade tolerance of P. capitatum, it was found out that P. capitatum has strong adaptability to shade environment. It could grow normally in about 100%-18% but not in 8.8% sunlight, and it could sprout in the next spring.In the arid environment, the water content of leaves of P. capitatum declined with the aggravation of drought stress. The plants of P. capitatum were restrained under drought stress. They were wilting lightly and the leaves got curled, there were more thichomes on the surface layer of the leaves in the 7th day without watering. The total content of chlorophyll, chlorophyll a content, chlorophyll b content and the ratio of chlorophyll a/b of P. capitatum raised with the lasting drought time, but the differences were not significant. The membrane permeability of the mesophyll, the soluble sugar content, the soluble protein, the proline content and the MDA content of P. capitatum increased severely when the plants were under drought stress.The SOD activity showed the tendency of declining firstly and then increasing under drought stress and decreasing at last. But there was no conspicuous difference between the contrast and those under water stress. P. capitatum would not be harmed until the soil moisture content was below 10%, but when watered nomally, the plants returned to fresh.In the PEG solution, the water content of leaves of P. capitatum declined with the aggravation when the PEG concentration increased. The total content of chlorophyll of P. capitatum increased when the plants were in PEG solution, and the membrane permeability of the mesophyll, the soluble sugar content, the soluble protein, the proline content of P. capitatum increased severely, too. The MDA content kept rising till the plants were in the PEG solution 12 hours, then it declined sharply. The SOD activity showed the tendency of declining firstly and then increasing and decreasing at last. In-0.1 MPa solution, P. capitatum could tolerate more than 24 hours. After 24 hours under-0.3MPa stress and 12 hours in-0.6MPa environment, the P. capitatum were slight wilting. After 12 hours in-1.5MPa low water potential environment, P. capitatum were wilting moderately, but they could restore normal growth when in 1/2 Hogland nutrient solution. While the P. capitatum were in-0.6MPa and -1.5MPa PEG solution for 24 hours, the plants were permanent wilting.According to the research on the shade and drought tolerance of P. capitatum, it was found out that P. capitatum has strong adaptability and tolerance to shade and drought environment, and it is a kind of nice ornamental plants which can be used as ground cover plants.

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