Effects Of Shading And Drought On The Physiology Index And Photosynthetic Characteristics Of Cenchrus Pauciflorus

Cenchrus pauciflorus was annual herb on gramineae Cenchrus. It was native to America tropics, and belonged to the alien invasive plants in our country. Cenchrus pauciflorus adaptability was strong, and it spread rapidly with great competitiveness. Cenchrus pauciflorus usually grew in sandy soil. In recent years, the Cenchrus pauciflorus as a kind of invasive species, severely damaged the local ecological system, not only damage the sustainable development of agriculture pasture, but also bring different degree of damage for people and livestock. At present, the research of Cenchrus pauciflorus was less, this test was to Cenchrus pauciflorus as the research object, under the condition of potted plants, simulate drought stress environment, set water stress gradient, and start different degrees of shading treatments. Measure the photosynthetic characteristics and protective enzyme, soluble protein and other physiological and biochemical indexes, for comprehensive analysis of Cenchrus pauciflorus on the stress environment adaptability and tolerance, predicting its distribution range of potential in our country, and to prevent its comprehensive control of ecological invasion and to provide the reference.The results of drought stress experiment showed that chlorophyll content in Cenchrus pauciflorus’ s leaves decrease to varying degrees as the drought stress intensifies. At the same time, there exists resistance in terms of its adaptation to drought stress environment. Under drought stress environment, MDA content and soluble protein related to its osmotic adjustment increase as the drought stress intensifies. This indicates its cellular membrane is injured, and lipid peroxidation effects are reinforced. After rewetting, MDA content and soluble protein decrease, which indicates the tolerability and restorability of its cell membrane are relatively strong. In antioxidant enzyme system, the enzyme activities of SOD, POD and CAT are analyzed. As drought stress intensifies, the enzyme activity, an indicator of its ability to remove active oxygen, is enhanced, thus improving its drought resistance and avoiding harms from active oxygen.Chlorophyll content in different treatments increased to varying degrees through the intensification of shading, which indicates Cenchrus pauciflorus’ s capability of resisting stress. Shading leads to light deficiency, the faster accumulation of free radical, increase of MDA content, and the decrease of soluble protein. As a result of the accumulation of free radical, antioxidant enzyme system displays certain effects. Therefore, SOD, POD, CAT and some other antioxidant enzymes increase in the prior period of shading, and undermine cellular membrane structure when the accumulated free radicals are beyond its defensive ability, thus leading to the reduced activities of the entire enzyme system.The photosynthesis of Cenchrus pauciflorus was seriously influenced by the drought and shading stress treatment. Its photosynthetic activity decelerated under the treatments. As the stresses intensify, net photosynthetic rate, stomatal conductance and transpiration rate of Cenchrus pauciflorus decrease. Under the interaction of stomatal and non-stomatal limitation factors, intercellular CO2 concentration increase to varying degrees. In addition, chlorophyll-fluorescence parameters are also changed by the stress treatments. FV/FM indicates efficiency of primary conversion of light energy of PSⅡ and also its potential activity. The primary photochemical activity of Cenchrus pauciflorus’ s PSⅡ when confronting stresses.These results provide experimental data to the future studies on the physiological adaptation mechanism of Cenchrus pauciflorus under stress environment, and offer insight into how to prevent the invasion of cenchrus pauciflorus.