Physiological and biochemical characteristics of Myricaria laxiflora,an endangered species in the Three Gorges Reservoir Area

In order to discover the physiological and biochemical characteristics in Myricaria laxiflora,an endangered species in Three Gorges Reservoir Area,the transpiration,photosynthesis,water potential of plant planted in two kinds of soils were tested in different growing seasons.Results showed that changes of transpiration,photosynthesis and water potential in a day all showed "single curve".Transpiration and photosynthesis could reach the maximum of a day at noon whereas water potential fall to the minimum.Transpiration changed with the fluctuation of photosynthesis.The photosynthesis and transpiration of plants in May were higher than that in October due to the plants in October just recover from the dormancy induced by flooding.PV-curve and relative water parameters,including Ψ100(maximum osmotic potential at water saturation point),Ψ0(osmotic potential when a plasmolysis just emerge),ROWC(relative osmotic water content),RWC(relative water content),AWC(relative water content in apoplast)and RDW(relative dry weight)of the plants grown in sandy soil,red soil and submerged soil were measured.Plants at submerge sandy soil having low Ψ100,Ψ0,AWC and high ROWC and RDW implied that submersion could promote plants to develop a good ability resisting dry stress.The biochemical contents related with stress resistance were tested in different growing seasons.Mlondialdehyde(MDA)content,peroxidase(POD)activity,Polyphenol oxidase(PPO)activity and total soluble sugar content decreased after flower and fructification.It suggested that the plant resistance declined after fruit.Some suggestions finally were put forward for the population transplant to conserve this species according to its physiological and biochemical characteristics.