Effects Of Different Water Stress On The Photosynthesis And Reladted Physiological Characteristics Of Photinia Frasery Dress Seedlings

Water stress usually includes water deficiency and flooding. The situation that water potential and turgor pressure in plant reduced to disturb or destroy its regular metabolize enginery and physiological function, caused by water deficiency is called water deficit stress or drought stress. And the situation that the water unbalance in plant caused by soil water stress nimiety or high atmosphere humidity could seriously influence the plant growth,output and quality, is named as waterlogging. When soil water content exceeds field capacity, the reducement of air in soil will cause the root breath weaken, or plant death.The apparentest responses of plant to environment stress shows in appearance. In general, there will be some evident symptoms like kraurotic leaves, curl, corrugation, speckle and so on. At the mean time, the growth and physiology of plant will be effectted by environment stress too. But the responses in appearance and growth are always later than physiological responses. Once the injury happens, it couldn't be resumed. So the studying of physiological responses to enviroment stress is not only helpful to open out physiological mechanism of acclimatizing plant to stress, but also redounding to the ability of resisting stress or protecting plant from stress, with the feasible technological measures. This paper used Photinia frasery Dress as experiment material, changes of photosynthetic charactreristic, pigment content, protective enzyme system and chlorophyll fluorescence characteristic of Photinia frasery Dress under drought were studied. The results showed that:1. Changes of Photosynthesis and Relative Physiological Characteristics of Photinia frasery Dress Seedlings under Different Drought in SpringAlong with the stress time extended and stress extent increased, leaf water content, photosynthetic pigment content and photosynthetic indexes of Photinia frasery Dress were inhibited in different levels, but the anthocyanin content, MDA content and membrane permeability increased distinctly.And protective enzymes (SOD,POD,CAT)activity first arised then declined. But at the same stage, the enzymes activity changed in different regulations when the stress degree pricked up. At the first and tenth day of experiment...