Molecular Mechanism Of Heavy Metals Toxicity And Tolerance In Rice (Oryza Sativa L.) And Wheat (Triticum Aestivum L.)

The damage of heavy metal to growth and development of rice(Oryza sativa L．)and wheat(Triticum aestivum L．)and The related molecular mechanisms were studiedfrom 1999 to 2002 Yangzhou with the polyacrylamide conncentration gradient gelwlectrophoresis technique,radioisotope trace kineic technique,HPLC technique,molecular biological technique and other physiologlcal measurement methods．Thetolerance mechanisms of rice and wheat to heavy metal stress was also analysed． 1 damages Rice and wheat were very sensitive to Cu~2+,Cd~2-,Hg~2+ stress at seedgernunatlon and seed！lug morphogenesls stagCs．me seed gernUnating percem旧驴decreased n the form of exponential decay with the CuZ",CdZ",HgZ"concentrationincreasing．he root elongation andthetlller aPPearance were sl即ificantly讪bitedby Cll'",Cd'",Hg"．D＊＊g。CtiVe VegCtatiVC gfOWth。lid gfs＊ ill＊g peflod,thesensitivity ofrice and wheat to CuZ",CdZ",HgZ"stress decreased obviously． Compared wun other orpans,the growth and devefopment of roots mostsignific咖ly nhibited by Cu'",C矿",Hg'"．The nhibition on tiller aPPearance册salso slgIUgIUfica血．here was a slgmgmfic用血 negative linear relationship be阿化en tillernmber and CuZ",CdZ",Hg"concemation．he nhlbltlon on stem elongation,leafeXpansion and grain deve…mQ血 was low As yield co呷onents,low concentration Cu'",Cd'",Hg"mainly nhAnted theformation of effective ears of nce and Wheat,high conemiration Cf",Cd'",Hg'"resulted n less gfams per panlcles and lower 000－grain weigh． rmong differs血 heawm咖Is,the order ofCuZ",CdZ",HgZ"Mibitiondegree onseen gennmatlon,root growth and tiller ppearance of nce and root grotvill of wheatwas CuZ"＞Cd'＋＞Hg'",Whil on leafandtiller ppearance ofwheat was Cd'"oHg"＞CuZ"． 2 Molecular mecban'sin ofdamage hephotosy讪etlc rate ofnce and wheatWs significamlyh山bitedby CuZ",Cd'",Hg｝ St爬SS．Cf",C扩",Hg'"C。used the C咖e血S Of photOSystem 11,photosystem,llgh harvesting plgnentTrotein complex and chlorophyll to decreasegfeatlyg and also wed the ratio of chlofophyll a／b,Which resulted in directnhibition on photos灿esis．Cu2＋,Cd'",Hg'"also disturbed the eXportaion ofphotosynthates from leaves and inhibited importation ofphotosynthates to sink o4ans．It was worth noting that the transformation ewen sta仰 and sllgar,s nhibited byCJ",Cd",Hg'"．Conseq砒ntlx S吧ar acem＂lated n the ieWes,Which ＂ugh nducea down－n唱＂lation of Calivn cycle,therefore,photosyllthetlc rate sic。d do。 he effect of heaVy metals on respration indicated that the respiratory rate n theleWes and roots of nce册s e讪anced by the low concent例ion of CJ",Cd'",Hg'",b吐 nib庇d加thehighconcelltratlon·Besides causing structml damagestoresPiratory aPParatUS,the inhibiting resPiration mechanism of CuZ＼ Cd",Hg》included:①啊lase actvity andsoZyIYles eXpression was inhibited,as a result,thedegTa恤ion of starch was blocked．②malate d劝ydrogenase activity and lsoWmes 162eXpression侧s nhib他d,hs,he tnc咖叮lic acid cycle was ob咖cted．③cytochrme oxldase activity and lsocymes expression was inhibited,hence,there叩lratory ele以丁on tfan叩ort slowed－doursl． 卫叱 c5缸咯e o(mabn山al4咖y6yco血出uO成a叨 by5e8Vy msmss m山cme4o劝CuZ",Cd'",Hg'"caused membrane 11pid Peroxidaion,among Which the ability ofCf"ca阳mg p皿x沾成bn删s the rdest．As a result of membranbranelipidperoxldalon,some p ortan physiological ictlons were altered:＠ he activaionenetgy of membrane－bound empmes increased, teopratUr of membrane phasechanges rose,nd rnelnbrane luldity decl＊ed；＠ the NaZ"－k'"－ATPase activity nchondria decreased,especially under the condition of low teopratUre thedecreasing was恤re slglllficant；③he freezing resistance ofwh...