| Using potted 2-year-old Fraxinus mandshurica as experiment materials and treated with different eight kinds of growth substance,simulating different soil water status,the effect of exogenous growth substance on photosynthetic parameters,WUE,membrane-lipid peroxidation and osmotic regulation of Fraxinus mandshurica under drought stress has been studied.In soil natural drought stress the inhibitory effect of ABA is remarkable when the soil water content is 32.67%-46.70%.The inhibitory effect of ABA is weaken gradually when the soil water content is 21.07%-30.14%.The inhibitory effect of exogenous ABA on Tr,Gs and Pn is lost when the soil water content is 15%-20%.The inhibitory effect of exogenous ABA on Tr,Gs and Pn has been resumed when the soil water content is 10%in severe drought stress. In the fast responses of photosynthetic parameters on ABA,the inhibitory effect of exogenous ABA on Tr,Gs and Pn is remarkable in drought stress.So it is indicated that ABA could enhance the resistance to drought of Fraxinus mandshurica under drought stress.The treatments of DA-6,Miao Huan,He Dong-li,SA and Feng Qiu increased Pn remarkably compared with CK,and increased the stomatal aperture of leaves.3000 times dilution treatment of Fu Xiao-fen-na had the effect of increasing Pn and Gs.High concentration treatment of brassinolide had the inhibitory effect on Pn,Gs and Tr,moreover low concentration treatment of brassinolide helped increasing the Pn,Gs and Tr of Fraxinus mandshurica.The treatments of DA-6,SA,Miao Huan and Feng Qiu increased the transpiration rate. Compared with two mensuration result of August and September,the stimulative effect of Fu Xiao-fen-na and He Dong-li on transpiration rate was remarkable.DA-6 treatments had increased WUE large scale.SA treatments could increase WUE,but there was no remarkable difference compared with CK.Miao Huan treatments decreased WUE. Compared with two mensuration result,600 times dilution treatments of He Dong-li could increase WUE moreover the effect of other concentration treatment was not remarkable.Early on drought stress the effect of Fu Xiao-fen-na treatments on WUE had been increased remarkably.Along with stress pick up,the WUE was decreased by Fu Xiao-fen-na treatments. In the medium-term of drought stress brassinolide and Feng Qiu had increased WUE better,but the effect was not remarkable in severe drought stress.In the fast responses of photosynthetic parameters on ABA,the inhibitory effect of exogenous ABA on Tr,Gs and Pn was remarkable in drought stress.There was remarkable inhibitory effect of exogenous ABA on Pn merely after 9 hours in normal water supply condition.When ABA reduces Tr and Gs at the same time not to reduce Pn large scale.The result of photosynthetic parameters diurnal variation showed that DA-6 increased Pn remarkably.The treatments of SA,Fu Xiao-fen-na,brassinolide,Miao Huan,He Dong-li and Feng Qiu had inhibitory effect on Photosynthesis and decreased Photosynthesis of Fraxinus mandshurica.DA-6 increased transpiration rate,decreased Stomata resistance of leaves and increased Stomatal conductance.The effect of SA on Tr and Gs was inhibitory in a short time of diurnal variation and was not remarkable after this.Fu Xiao-fen-na and brassinolide treatments decreased Tr better,and decreased Gs in a short time of diurnal variation but effect was not remarkable after this.Miao Huan,He Dong-li and Feng Qiu has effect of enhancing Tr and Gs in a short time of diurnal variation,but there was inhibitory effect on Tr and Gs at the end of diurnal variation.Under drought stress SOD activity,POD activity and soluble protein content of Fu Xiao-fen -na,brassinolide,Miao Huan,He Dong-li,Feng Qiu,SA and DA-6 treatments had enhanced remarkably.Soluble sugar content of brassinolide,He Dong-li,Miao Huan,Feng Qiu and SA treatments had increased,but difference compared with CK was not remarkable. Soluble sugar content of Fu Xiao-fen-na and DA-6 treatments had decreased at the end of drought stress,but difference compared with CK was not remarkable.
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