Physiological Response Of Four Woody Species To Lead Stress

Along with urbanization and industrialisation,lead polution in city is so serious that has side effect on urban ecological system,so the study on physiological response of species to lead stress is important for urban ecological system.Studies on the physiological characteristics and mechanism of leaves in Loropetalum chinese(R.Rr.) Oliv.,Platycladus orientalis(L.) Endll,Acacia famesiana(Linn.) Willd, Populusdeltoides×Populus nigra were carried out under four lead gradient(0,300,450 and 600 mg·kg^-1).The changes on physiological characteristics were measured and analyzed under lead stress.The results were as follows:1) With lead stress increasing,the membrane permeability and content of MDA in four species increased.The most changes happened on Acacia famesiana(Linn.) Willd which were respective 75%,54%,while the least happened on Populusdeltoides×Populus nigra which were respective 33%,24%.2) As an key osmotica,Proline increased obviously(p＜0.05) in Populusdeltoides×Populus nigra,Platycladus orientalis(L.) Endll and Loropetalum chinese(R.Rr.) Oliv which maximal inceaseing accured in Platycladus orientalis(L.) Endll with 62%.The changes of dissoluble sugar in four spciese resmbled with pro which maximal inceaseing accured in Populusdeltoides×Populus nigra.The dissoluble protein in Loropetalum chinese(R.Rr.) Oliv.,Platycladus orientalis(L.) Endll,Populusdeltoides×Populus nigra had inceased while the obviously(p＜0.05) change accured in Populusdeltoides×Populus nigra.3) Under lead conditions,the activity of SOD,POD of Populusdeltoides×Populus nigra,Platycladus orientalis(L.) Endll and Loropetalum chinese(R.Rr.) Oliv increased markedly(p＜0.05) which maximal inceaseing accured in Populusdeltoides×Populus nigra with respectively 800 U·g^-1,103 U·g^-1·min^-1,while Acacia famesiana(Linn.) Willd decreased when the lead stress beyond 450 mg·kg^-1.4) Lead stress had an positive impact on the photosynthetic system of Populusdeltoides×Populus nigra,Platycladus orientalis(L.) Endll and Loropetalum chinese(R.Rr.) Oliv while negative impact on Acacia famesiana(Linn.) Willd.5) The photosynthetic factor contained by chlorophyll and photosynthetic speed is most important for resistance of lead for species,so Populusdeltoides×Populus nigra and Platycladus orientalis(L.) Endll have strong resistance which photosynthetic factor work well.6) The resistance of lead on the four species was assessment by using all the sensitive physiological indicators.The ability of lead-resistance was: Populusdeltoides×Populus nigra＞Platycladus orientalis(L.) Endll＞Loropetalum chinese(R.Rr.) Oliv.＞Acacia famesiana(Linn.) Willd.