Effects Of Environment Factors On Photosynthetic Characteristics And Several Physiological And Biochemical Indexes Of Cowpea

Light,CO₂ and temperature are important environmental factors that affect plant growth and development. The research about effects of Light quality,CO₂ concentration and temperature on photosynthesis and physiology of cowpea has not been reported.Therefore,with cowpea seeds of the United States as test materials,4 different light quality,4 different CO₂ concentrations and 6 different temperature levels on photosynthetic characteristics and physiological and biochemical indexes were studied in order to provide the theory basis of good quality and efficiency cultivation.1.Effects of different light quality on photosynthetic characteristics and physiological and biochemical indexes of CowpeaLight quality had great effect on photosynthesis of cowpea leaves. Red light was conducive to increase the content of chlorophyll(Chl), while Blue light could increase the content of carotenoids(Car).The photosynthetic rate and transpiration rate of cowpea had different level of increase in different light,the order from high to low was red light>white light>green light>blue light.Light quality could adjust the carbohydrate and protein metabolism of higher plants. Compared with red and green light,blue light could significantly thrive nitrogen metabolism of cowpea,and the content of protein was higher,while the content of soluble sugar was improved the most significant under the red light treatment.The cowpea under different light quality, SOD, POD and CAT activity were increased at first and then decreased,enzyme activity was higher in full growth period than that of other period,which is the universal law of growth and development,light quality did not change this rule,just made it more significant.MDA is an important indicator that used to measure lipid peroxidation,red, blue and green light could reduce the MDA content in leaves of cowpea, and the effect of green light was the most significant.2.Effects of different CO₂ concentrations on photosynthetic characteristics and physiological and biochemical indexes of CowpeaUnder different CO₂ concentrations,the photosynthetic pigment content elevated with the increase of CO₂ concentration. CO₂ concentrations could obviously increase the photosynthetic rate of cowpea,but the transpiration rate in the 800ml·m-3,1200 ml·m-3 and 1600 ml·m-3 CO₂ concentrations had different levels of decreases compared with the atmospheric CO₂ concentrations.CO₂ fertilization could increase photosynthetic rate and accumulate carbohydrates,the results showed that the soluble sugar content increased significantly with CO₂ concentration.The soluble protein content was increased at different degree in high concentrations of CO₂ than low CO₂ concentration,in which 1200 ml·m-3 had the highest growth rate.SOD,POD,CAT changed greatly in different CO₂ concentrations, the enzyme activity at 1200 ml·m-3 was at the highest level.The enzyme activity was relatively high in metabolic exuberan, while the activity was low in the condition of aging or stress. High concentrations of CO₂ decreased free radicals,which consolidated the balance between generation and removal system, reduced lipid peroxidation and made the MDA level lower in cowpea leaves,anti-aging.3.Effects of different temperature on physiological and biochemical indexes of Cowpea Temperature stress on plants can cause general oxidative stress,then affects the plant physiological and biochemical processes.The photosynthetic pigment contents was significant different at different temperatures,the value were higher at 20℃and 25℃,higher or lower temperatures forced the photosynthetic pigment content of cowpea leaf to decrease.The soluble sugar content and soluble protein content were highest at the optimum temperature 25℃. POD activity, CAT activity and MDA content increased gradually in heat or cold stress,while SOD activity showed a reverse downward trend.At 10℃, MDA content had the highest level and the protective enzyme activity at the lowest level, indicating that the stress of low temperature played an greater role on cowpea than high temperature,this was exactly the reflection of thermophilic characteristics of cowpea.The best light quality,CO₂ concentration and temperature should be chosen according to different needs of cowpea in production to enhance the positive effect on growth and development,then high quality and effective cultivation would come true easier.