| Reaumuria soongorica,the perennial shrub belonging to genus Reaumuria,family Tamariskaceae,it is a typical desert ecological tree species and has great significance for ecological protection in desert areas.Drought,as one of the inevitable abiotic stresses in the process of plant growth in desert areas,has greatly affected the vegetation restoration and growth of Reaumuria soongorica.It is of great significance to study the exogenous substances to alleviate the damage of drought for the reproduction and protection of Reaumuria soongorica population.In this study,An outdoor experiment was conducted to investigate the effects of exogenous ABA(2,4,6,and 8 mg·L-1)and exogenous Pro(50,100,150,200,and 250 mg·L-1)at different concentrations on the physiological characteristics on the leaves of the multi-age,Reaumuria soongorica,all under natural field environmental drought conditions.The main results are as follows:1.The content of osmotic substances?SS,free Pro and SP?in the leaves of Reaumuria soongorica were reduced by exogenous ABA,and relieves the pressure of osmotic substance adjustment;At the same time,the activities of antioxidant enzyme?SOD,POD,CAT?were increased with sprayed ABA,and the ROS clearance effect was promoted.The degradation of chlorophyll were relieved,and reduction of Chl?a+b?,Chl a,and Chl b content and increase of Chl a/b value were suppressed;the stomatal conductance?Gs?,transpiration rate?Tr?,and intercellular CO2concentration?Ci?were further reduced with the addition of exogenous ABA,which improved the water retention capacity of Reaumuria soongorica leaf cells.At the same time,the decline in net photosynthetic rate?Pn?was alleviated,and water use efficiency?WUE?was increased.The reduction of Pn in Reaumuria soongorica under drought stress is not only the result of stomatal limitation,but also factors other than stomatal limitation;the application of exogenous ABA also alleviated the decrease of Fm,Fv/Fm,and qP,the increase of F0 and NPQ were relieved.It had a certain protective effect on PS?of Reaumuria soongorica leaves,and could reduce the damage of photosynthetic apparatus by drought.2.The content of soluble protein?SP?in the leaves of Reaumuria soongorica were increased by exogenous Pro,and the content of soluble sugar?SS?,free proline?Pro?were reduced;the activities of superoxide dismutase?SOD?,peroxidase?POD?and catalase?CAT?were increased with sprayed Pro.It can also increase the content of Chl?a+b?,Chl a,and Chl b in Reaumuria soongorica leaves,reduce the value of Chl a/b,and promote the synthesis of chlorophyll;At the same time,Pn,Gs,Tr,Ci and WUE of Reaumuria soongorica leaves all increased to some extent;exogenous Pro treatment can also increase the activity of PS?reaction center,promote electron transfer,the increase of F0 and NPQ and the decrease of Fm and Fv/Fm were alleviated.At the same time,qP was increased,and the light suppression caused by drought stress was alleviated.3.Exogenous ABA and exogenous Pro are coordinated with each other in a variety of ways to alleviate the damage caused by drought stress to Reaumuria soongorica,which is mainly reflected in two aspects:maintaining water balance and improving tolerance of cells of Reaumuria soongorica.4.Exogenous ABA and exogenous Pro had a concentration effect on the relief of drought stress in Reaumuria soongorica.Using the membership function method to comprehensively analyze and compare the mitigation effects of the two exogenous substances,it is found that the treatment effect of exogenous ABA at a concentration of 6 mg·L-1 is the most obvious.When the concentration is lower or exceeds this concentration,the effect will be weakened;Spraying at a concentration of 100 mg·L-1of exogenous Pro obtained the most optimal results,however,the high concentration of 250 mg·L-1 treatment will further strengthen the damage to the Reaumuria soongorica.The treatment of exogenous substances also has a time effect,with increasing the number of treatment days,it was observed that the effect decreased.It was found that exogenous Pro treatment was better than exogenous ABA treatment in alleviating the damage of drought stress to Reaumuria soongorica by comparing the two exogenous substances. |
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