Drought Tolerance Of Cleistogenes Songorica

Cleistogenes songorica is a native forage plant with characteristics of drought tolerance and fine quality for livestock. It distributes mainly in the area of desert grassland in norhtwestern China, and plays a vital role in environmental protection and livestock production. A series of pot experiments and field trials was undertaken to understand mechanisms of its drought tolerance with comparison with tall fescue (Festuca arundinacea). The main research outcomes are summarized below.Cleistogenes songoric growing under the drought conditions created by watering pot plants at the 9 day intervals.showed higher dry matter yields than those growing under less drought stress conditions watered at 3 or 6 day intervals. C. songorica had the higher dry matter yields than tall fescue growing under the same drought stree conditions. In subsequent soil drought treatment C. songorica take a longer period than tall fescue to show the permanent wilting symptom. The higher dry matter production, higher relative water content of leaf and higher leaf chlorophyll content were obtained from plants of C. songorica watered at 9 day invervals than those water at more frequently, which indicated that C.songori have better drought tolerance. As the drought condition becoming more severe, the soil volumetric water content and leaf relative water content of tall fescue decreased more remarkably than those of C. songorica. During drought stress, plasma membrane permeability in C. songorica was increasing correlated with the malondialdehyde (MDA) content significantly Soluble protein content and activities of Superoxide Dismutase(SOD),Peroxidase (POD) and Catalase (CAT) in C. songorica shows an increase in the early phase of drought and then a decrease with further increase in magnitude of water stress, these physiological responses in roots were more sensitive than those of in leaves. Those changes occurred in tall fescue prior to those in C. songorica. Contents of total sugar content (TSC), sucrose and fructose in leaf and root of C. songorica showed a sustainng increase with the prolong period of drought stress. Contents of amino acid and praline did not appear a regular change in C. songorica, but increased steadily in leaf and root of tall fescue under the same drought conditions Contents of K⁺,Ca²⁺,Mg²⁺ trended to increase sustaining in leaf and root of C. songorica with the longer period of drought stress. Rank of contents of three ions accumulated in leaves and roots of C. songorica was: K⁺> Ca²⁺> Mg²⁺.The results mentioned above shows that TSC was the important osmoticum in leaves and roots of C. songorica under drought stress, and sucrose and fructose were two primary components in TSC and were also primary formation which TSC accumulated under drought stress. Different from C. songorica, amino acid and praline were important osmoticum accumulated in tall fescue, increasing praline content might be primary reason why amino acid acculumated. K⁺ was important osmoticum in leaf and root of C. songorica, in which leaf was the primary organ for accumulation of K⁺ under drought stress.The net photosynthetic rat (Pn), transpiration rate (Tr), stomatal conductance (Cs), water using efficiency (WUE) and apparent quantum yield of photosynthesis (AQY) declined while intercellular CO₂ concentration (Ci) and light compensation point (LCPs) increased for both plant species tested. Pn, WUE, AQY in C. songorica were higher than those of tall fescue, while Tr, LCPs in C. songorica were lower than those of tall fescue. These data showed that C. songorica had higher photosynthetic rate and water using efficiency than tall fescue under same drought stress.Summarise above we concluded that C. songorica has better drougt tolerance ability than tall fescue does.