Studies On Photosynthetic Characteristics And Drought Resistance Of Four Caraganas Species

Caragana is a typical plant found in drought and desert areas and is extensively used in wind,sand,soil and water conservation,for improving soil properties and drought resistance which are of great significance in ecological restoration and reconstruction in desert regions.In this study we selected four species of caragana leaves as the experiment materials to investigate and compare the drought resistance mechanism of different species of eremophytes in respects of ecological characteristics and physiological metabolism and morphology using a mathematical membership function method,to convert each index factor data.The results of our study are as follows:?1?the curve of diurnal variation of net photosynthetic rate?Pn?and transpiration rate were double peak curves in both caragana bushes,except C.acanthophylla Kom,which exhibited a single peak curve.The LSP,LCP,AQY,Rd and Pn_max in the four caragana shrubs were 1798.9 and 1586.81?mol·m^-2·s^-1,51.76 and 36.76?mol·m^-2·s^-1,0.08 and 0.05,24.74 and 10.82?mol·m^-2·s^-1 respectively.The data indicated four caragana shrubs need strong light but was insensitive to weak light.Therefore,the influence order of light intensity in the four Caragana shrubs were:C.davazamcii Sancz>C.korshinskii Kom>C.acanthophylla Kom>C.rosea Turcz Maxim.Decrease in Pn in the shrubs,including C.davazamcii Sancz and C.rosea Turcz Maxim,were caused by non-stomatal limitation,but the other shrubs were caused by stomatal limitation under extreme environmental conditions.Relative humidity was the main environmental factors affecting Pn for C.korshinskii Kom.In addition to CO₂concentration in the air,had an important restrictively impact on Pn though the effects were small in the other shrubs.?2?Under drought stress,physiological and biochemical indexes of four kinds of Caragana changes reflect the drought resistance.The leaf water content,relative water content and leaf water potential,with the degree of drought stress increased and gradually decreased.The leaf water potential and soil moisture content was proportional to the water potential.In terms of drought resistance ability,Caragana.korshinskii.Kom was maximum while C.rosea Turcz was minimum.In leaf water content and leaf water saturation deficit judgment strongest drought resistance shrub followed the order:C.davazamcii Sancz>C.korshinskii Kom>C.rosea Turcz.Under natural drought conditions,the lowest drought resistant of the four kinds of Caragana adjusted leaf water content and water potential to improve the drought resistance ability.?3?Changes in RWC,WSD,WP,chlorophyll,free Pro,SOD,POD and MDA of four kinds of Caragana,indicated that drought stress has a significant impact on the chlorophyll fluorescence parameters of Coreopsis since the range of changes of chlorophyll fluorescence parameters of different species of Caragana was different.The content of malondialde hyde?MDA?rate of four plants from different areas were increased under the water deficit,and it destroyed the cytomembrane.The content of proline and soluble protein of four kinds of drought resistance were in the order:C.acanthophylla Kom>Caragana.intermedia.Kuang>C.korshinskii Kom>C.rosea Turcz Maxim.Using MDA to determine four kinds of drought resistance of Caragana,the order was:C.davazamcii Sancz>C.acanthophylla Kom>C.korshinskii Kom>C.rosea Turcz Maxim.Using super oxide dismutase?SOD?was much more remarkable where C.acanthophylla Kom>C.davazamcii Sancz>C.korshinskii Kom>C.rosea Turcz Maxim.While the effect of peroxide enzyme?POD?and catalase?CAT?was not remarkable in protecting the plants under the drought stress.?4?Sorting the ability of drought-resistance of Caragana genus using fuzzy mathematics,sixteen drought resistant indexes were restricted and relied on each other in the drought resistant mechanisms of four plants:C.korshinskii Kom>C.acanthophylla Kom>C.aragana.intermedia.Kuang>C.rosea Turcz Maxim.Using sixteen drought resistant with the grey correlation method,the drought-tolerance ability of different Caragana in drought stress condition by comprehensive appraisal index were as follows:Water Use Efficiency>free water/bound water>Superoxide Dismutase Proline>relative water content>Peroxide Enzyme>Water Potential>leaf relative water content>Malondehyde>Water Saturation Deficit>Pn>soluble proteins>Ratio of Chlorophyll a to b>Peroxide Enzyme>Catalase>Chlorophyll?a+b?.Water Use Efficiency?free water/bound water?Superoxide Dismutase and Proline can be considered an important for drought-resistance.