Effects Of Pretreatment Of Water Stress On Photosynthetic Characteristics Of Fall Fescue And Control Of Exogenous Hormones

The grass which is not taken seriously in the long time is important to our living environment. The grass can not only inhibit the dust, prevent soil erosion,and form an important ecological barrier, but also can create a good living environment.At present the reasons of grassland degradation in China are not only Man-made causes ,and in arid and semi-arid regions lacking of water is an important reason of grassland degradation. So developing drought grasses have a very positive meaning.A large number of studies have shown that water deficit is not entirely a negative effect, the plants which were subjected to moderate droughts generally exist compensation effect.Imposing favorable hormone on crops can ease the plant in the physiological functions under stress disorder, exogenous salicylic acid can improve the resistance of plants to stress, so pretreatment of water stress and exogenous salicylic acid treating on tall fescue to water stress may improve drought resistance of tall fescue. Therefore, we can discuss effect of different treatments on drought-resistance of tall fescue by researching photosynthesis the tall fescues have been treated under water stress,in order to find the method of improving tall fescue in response to drought stress in the photosynthetic capacity.As the material of tall fescue ,in the method of soil culture,this experient is carried out to study several physiological changes with photosynthesis the tall fescues under water stress by reserching on single pretreatment of water stress on seeding , single pretreatment of water stress on seeding and exogenous salicylic acid treating on seed in together,single exogenous salicylic acid treating on seed.First,the research of effect of single pretreatment of water stress on photosynthesis of tall fescue has studied.The results showed that pretreatment can make tall fescue acclimatize itself to the water restress quickly and decrease water stress doing harm to photosynthesis of tall fescue. The resistance of drought stress on pretreatment photosynthesis of tall fescue is by inhibiting stomatal conductance to achieve, but the tall fescue without the stress of water pre-treatment in the late drought stress decreased the photosynthetic rate ,the main reason for the decline in stomatal conductance is the change in non-stomatal limitation. water pre-treatment can ease the damage of drought stress on tall fescue light to PSII reaction center, inhibit the reduction of QA in tall fescue under water stress decreased ,in order to increase the PSII of Electron transport activity, ease the primary photochemical activity of PSII of tall fescue under drought stress to be inhibited, slow the photochemical pathway of excitation energy excitation energy intoΦPSII of tall fescue which is used to account for reduce the proportion of the total rate, improve the apparent electron transfer rate of tall fescue under drought stress and reduce non-radiative energy dissipation of tall fescue under drought stress. Then the research of effect of the other Two pretreatments of water stress on photosynthesis of tall fescue has studied. We found that the other Two pretreatments of water stress on photosynthesis of tall fescue have played a role in strengthening.It is similar to the effect of single pretreatment of water stress,but with different degrees.Finally,compared to the effect in increasing photosynthesis three different pretreatments of water stress on tall fescue,it is found that single pretreatment of water stress and exogenous salicylic acid treating in together has the best effect.And single exogenous salicylic acid treating has a not significant effect.