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Morphological And Physiological Responses To UV-B Radiation In Duckweeds: Spirodela Polyrhiza

Posted on:2004-10-12Degree:MasterType:Thesis
Country:ChinaCandidate:J H ShiFull Text:PDF
GTID:2120360092487810Subject:Optics
Abstract/Summary:PDF Full Text Request
With the depletion of ozone layer in stratosphere, solar UV-B radiation on theearth surface is increasing. Plants use sunlight for photosynthesis, and it is inevitable that they are affected by enhanced UV-B in the sunlight. Effects of UV-B radiation on the morphological structure and physiological biochemistry in leafy thallus of Spirodela polyrhiza were investigated in the present study.Spirodela polyrhiza were grown under UV-B radiation at the irradiance of 2.8 W/m2 from 9:00-15:00 every day, and control duckweeds were placed in the natural light in the laboratory. Experimental results indicated that supplemental UV-B radiation decreased the number of leafy thallus and retarded the growth of leafy thallus. Under the natural conditions, these effects of UV-B radiation will cause far-reaching biological and ecological significance. Activity of phenylalanine ammonia-lyase (PAL) was increased by UV-B radiation, and as a consequence, UV-absorbing compounds were accumulated. It was inferred from our results that the accumulation of UV-absorbing compounds such as flavonoids may be a common response for plants in resistant to enhanced UV-B radiation. Enhanced UV-B radiation greatly decreased the content of photosynthetic pigments: chlorophyll a, chlorophyll b, and total chlorophyll. Supplemental UV-B radiation induced the antioxidant system change. Activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were increased. The analysis indicated that plants have internal resistant mechanism against UV-B damage. Perhaps the changes of antioxidant system were caused by the accumulation of free radicals and activated oxygen. The electrolyte leakage from the duckweed's cell increased by enhanced UV-B radiation with the increasing time of treatment. Perhaps lipid peroxidation is one of the causes of membrane damage, and reactive oxygen species (ROS) were involved in the process.
Keywords/Search Tags:antioxidant system, flavonoids, membrane permeability, reactive oxygen species (ROS), UV-absorbing compounds, UV-B radiation
PDF Full Text Request
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