Physiological Response Of Eight Tree Species To Drought Stress And Evaluation Of Drought Resistance

We need to select tree species with the ability of stronger drought resistance and strongeradaptability when afforestation in arid and semiarid areas or drought and barren mountainousregion. And the premise of selecting tree species is to realize the drought adaptability and themechanism of drought resistance. We measured three broadleaved tree species and fiveeconomic tree species’ physiological parameters by potting experiment under continuousdrought stress. We researched the physiological response of the trees to soil drought stress andcompared the differences of trees among drought resistance physiology. Zhenzhuyouxingapricot is one indigenous tree species with economy development potential in Taian and evennorth China area. We measured Zhenzhuyouxing apricot’s photosynthetic response process tolight under different soil moister conditions, then we investigate the effect of soil moistureand light intensities on photosynthetic. At last, we evaluate eight tree species’ droughttolerance, and the order by subordinate function and so on. The results will provide scientificreference for the tree species choices of afforestation in north China’s drought and barrenmountainous region and vegetation recovery.The main results as follows:(1) The responses of various physiology indexes among various tree species to soildrought stress are different, so drought resisting mechanisms among various tree species arediverse.With the aggravation of drought stress, the MDA content and cell membranepermeability of three arbor species increased all the way. The MDA content of five economictree species increased or decreased in experiment, later stage, the MDA content ofXanthoceras sorbifolia Bunge and Prunus ansu Kom are very high, and the cell membranepermeability are also very high. The MDA content of Diospyros kaki Linn.f.、Zanthoxylumbungeanum Maxim. and Zhenzhuyouxing apricot steadied in a low level, and at later stage,the cell membrane permeability of three arbor species were low.With the aggravation of drought stress, Acer mono Maxim. and Ailanthus altissimaSwingl. and Zhenzhuyouxing apricot’s SOD activity rised at first, and then dropped, whilePistacia chinensis Bunge’s SOD activity rised at first and then dropped, at last rised again,and Diospyros kaki Linn.f., Zanthoxylum bungeanum Maxim., Xanthoceras sorbifolia Bungeand Prunus ansu Kom.’s SOD activity rised all the way. The SOD activity of Ailanthusaltissima Swingl. and Pistacia chinensis Bunge were higher than Acer mono Maxim. TheSOD activity of Acer mono Maxim. was lowest, and at later stage, the MDA content of Acer mono Maxim. was highest. At later stage, The SOD activity of Xanthoceras sorbifolia Bungeand Diospyros kaki Linn.f. rised quickly, and their MDA content decreased quickly orremained in a low level.With the aggravation of drought stress, proline content of the three arbor tree speciesincreased all the way, and the content increased quickly at later stage. The proline content atlater stage increased dozens of times more than at the stage of tree in appropriate soil moisture.After middle stage, the proline content of five economic tree species were also increased, withthe aggravation of drought stress, increased more quickly. The leaf relative water content ofeight tree species decreased all the way, and all decreased slowly at earlier stage, decreasedquickly at later stage.Acer mono Maxim., Ailanthus altissima Swingl. and Xanthoceras sorbifolia Bunge’schlorophyll content rised at first and then dropped, while Pistacia chinensis Bunge andPrunus ansu Kom.’s chlorophyll content had no distinct variation between pretest and posttest.Diospyros kaki Linn.f.’s chlorophyll content rised all the way, and Zanthoxylum bungeanumMaxim. and Zhenzhuyouxing apricot’s chlorophyll content rised at first and then dropped, atlast rised again. As a whole, the order of the chlorophyll content of three arbor tree species isAilanthus altissima Swingl.>Acer mono Maxim.>Pistacia chinensis Bunge, and the order ofthe chlorophyll content of five economic tree species is Diospyros kaki Linn.f.> Zanthoxylumbungeanum Maxim.> Zhenzhuyouxing apricot, and the content of Xanthoceras sorbifoliaBunge and Prunus ansu Kom. are lowest.The maximum net photosynthetic rate occurred in the range of50%~85%of the relativesoil water contents, after the range, net photosynthetic rate decreased. After T3gradient, netphotosynthetic rate and transpiration reduced as the degree of drought stress increased, andthe decreased degree were large. Ailanthus altissima Swingl., Pistacia chinensis Bunge,Diospyros kaki Linn.f. and Zanthoxylum bungeanum Maxim.’s water use efficiency of leafdropped at first and then rised,at last dropped again, while Acer mono Maxim. and Prunusansu Kom.’s water use efficiency of leaf rised at first, and then dropped. Xanthocerassorbifolia Bunge’s water use efficiency of leaf dropped gently, and Zhenzhuyouxing apricot’schange of water use efficiency was not obvious at earlier stage, then dropped at later stage.（2）When the relative soil moister were from43.6%to84.7%, the photosyntheticactive radiation were from800to2000μmol·m-2·s-1, it is good for Zhenzhuyouxing apricot toconduct Higher net photosynthetic rate and water use efficiency. Stomata limitation is themain reason result in lower net photosynthetic rate when the soil moister were from43.6%to73.5%, and non-stomatal limitation result in lower net photosynthetic rate when the relative soil water moister were less than43.6%. Finally, We could come to the conclusion that thezhenzhuyouxing apricot is a very strong drought resistance plant.（3）The subordinate function was used to rank their drought tolerance, and the orderwas: Ailanthus altissima Swingl.> Pistacia chinensis Bunge> Acer mono Maxim.. We knewproline, SOD and leaf relative water content were the key indicators to evaluate the droughtresistance of the three tree species by grey correlation analysis.（4）The subordinate function was used to rank their drought tolerance, and the orderwas: Diospyros kaki Linn.f.> Zanthoxylum bungeanum Maxim.> zhenzhuyouxing apricot>Xanthoceras sorbifolia Bunge> Prunus ansu Kom.. The order of using coordinate evaluationof multidimensional space was: Zanthoxylum bungeanum Maxim.> Diospyros kaki Linn.f.>Xanthoceras sorbifolia Bunge> zhenzhuyouxing apricot> Prunus ansu Kom.. Both twomethods using for rank five economic tree species’ drought tolerance is well. Through thecomprehensive comparison, We classified Diospyros kaki Linn.f. and Zanthoxylumbungeanum Maxim. as the most drought resistant trees, zhenzhuyouxing apricot andXanthoceras sorbifolia Bunge as the medium level of drought resistant trees, and the Prunusansu Kom. as the low drought resistant trees.