大量元素钾课件

第四章植物大量元素（钾）Section1GeneralIngeneral,K20contentinplantsisabout0.3~5%ofdryweight.主要农作物不同部位中钾的含量（%）作物部位含K2O作物部位含K2O小麦籽粒0.61水稻籽粒0.30茎杆0.73茎秆0.90棉花籽粒0.90马铃薯块茎2.28茎杆1.10叶片1.81玉米籽粒0.40糖用甜菜根2.13茎杆1.60块茎5.01谷子籽粒0.20烟草叶片4.10茎秆1.30茎2.80

ThereisastableKconcentrationincytoplasm,whichisabout100~200mM,theotherKstoresatthevacuole.

干物质含钾量（%）细胞质液泡012345K+浓度(nmol/l)3002001000UnlikeNandP,Kexistsinplantasanion(K+),anddoesnotformstablecomplexes.NutritionfunctionofK+involves:neutralizingthesolubleandinsolubleanion;StablingpHbetween7and8;Regulatingosmoticpressure;Enzymeactivation;Adaptationtostress---------Enzymeactivation

Therearemorethan60enzymeswhicheithercompletelydependonorarestimulatedbyK+.

ATPase,pyruvatekinase（果糖激酶）6-phosphofructokinase（6-磷酸果糖激酶）Photosynthesis

InhigherplantsK+affectsphotosynthesisatvariouslevels:※Enhancingchlorophyllsynthesis;※Improvingchloroplaststructure;※IncreasingCO2fixation;※Improvingcarbohydratetransport.Osmoregulation

K+isthedominantosmoticsubstances.

CellextensionistheconsequenceoftheaccumulationinthecellsofK+.

StomatalMovement

InmostspeciesK+hasthemajorresponsibilityforturgorchangesintheguardcellsduringstomatamovement.

AnincreaseintheK+concentrationintheguardcellsresultsintheuptakeofwaterfromtheadjacentcellsandacorrespondingincreaseinturgorintheguardcellsandthusthestomataopening.ImprovingthetoleranceofplantstostressDrought;Hightemperature;Cold;Disease;Salt;Lodging-----

SuitableKcanImprovecropquality:IncreasingproteinandammoniaacidcompositionIncreasingsugarsandstarchcontent;Enhancingvitaminsinvegetables;Delayingstorageperiod;Improvingcommercialquality;----------Qualityelement!!缺素症状植株生长缓慢,矮化;下部老叶叶缘先发黄，然后变褐、焦枯；有些作物叶片呈青铜色，向下卷曲，叶表叶肉突起，叶脉下陷；根系生长不良，色泽黄褐；种子、果实小，产量低，品质差；早衰。yellowing,followedbytissuedeath,progressinginwardalongthemarginsofolderleaves.烟草：叶片小、叶尖端黄化，叶缘间失绿发黄，有褐色坏死斑点。缺钾油菜从叶缘开始黄化，沿叶脉间失绿，有褐色斑点或局部有白色干枯组织芹菜缺钾严重缺钾时，叶缘发焦，似灼伤状番茄缺钾左为正常果实，右为缺钾果实，有绿背缺钾果实着色不均匀，有时有棱角，果实发育不良，汁液少，内空，多为等外果上为缺钾叶片，下为缺镁叶片，缺钾的叶缘症状更为明显萝卜缺钾叶片自右至左缺钾加重，叶缘呈灼伤状

我国钾肥目前的市场需求在600万吨以上，而且这一数字还将以每年5%左右的速度递增。但目前我国的钾肥产量仅有50—60万吨。

中国最大的钾镁盐湖——察尔汗盐湖(面积达5000多平方公里的大盐湖，是世界上海拔最高的内陆盐湖),氯化钾储量为１.45亿吨。

1996年生产能力达５０万吨。

青海１００万吨钾肥项目建设工程完成？ThereisanequilibriumbetweenthevariousformsOrganicKisonlyasmallpart.ReleaseandfixationofK+andNH4+ionsbysoilclaySection2MolecularandphysiologicalaspectsofpotassiumuptakeinplantsKisthemostabundantcellularcation,withcytoplasmicconcentrationsregulatedbetween80and200mM,andtotaltissueconcentrationsofapproximately20mM.ThetransportofK+,whichismobileinplant,hasbeenstudiedintensivelyforthelast50years.K+转运进入植物和在植物中运输的模式图2.1EarlyPhysiologicalandbiochemicalstudiesindicatedtheexistenceofmultipleK+transportersExcitedroots(HoaglantandBroyer，1936）Epsteinwasfirsttotreatradioisotopestoquantifyionefflux.Epsteinwasfirsttotreatmineraliontransportersasenzymekineticstostudiesofconcentration-dependentrootK+uptake.DualisothermofKabsorptionHigh-affinityK+transportwasthoughttodominateatlowconcentrationofK+insoil,whereasashigherK+concentrations,alow-affinityK+transporteroperatedthatwaslessspecificforK+overotheralkalications.硫基修饰的N–乙基马来亚铵（NEM）:抑制髙亲和力转运蛋白但不影响低亲和力转运蛋白。Physiologicalstudiesprovidedfurtherevidenceforseparatehighandlow-affinityK+transportersTheapplicationofaK+-channelblockerTEA(四乙铵)inhibitedthelinear,low-affinitytransportcomponent.High-affinityK+uptakesystemexhibitedseveralproperties:IncreasinggeneexpressionortransportactivityinducedbyK+starvation;AveryhighaffinityforK+(Km=5to30µM);AstrongselectivityforK+andRb+overotheralkalications.Low-affinityK+uptakesystem:

LessselectiveforK+andRb+;LessinfluencedbychangesintheK+statusoftheplant.2.2MechanisticbasisforHigh-andlow-affinityK+uptakesystem利用电生理技术，将玉米低盐根置于低钾（2～20µM）溶液中将引起膜电位的强烈的去极化。而在更髙的浓度（>0.5mM）时，去极化减弱。植物中存在两种类型的K+通道：

内流型通道（inwardrectifyK进）和外流型通道（outwardrectifyK出）内流型通道（K进）在Em（<－50～－150mV）超极化时打开促使吸收K+。而外流型通道（K出）在Em去极化时打开并将K+运出细胞。研究表明低亲和性钾吸收的1个主要成分是内向整流通道（K进）。植物中内流型通道（K进）不易失活，可以长时间保持开放。内流型通道和外流型通道均具有较高的K+/Na+选择性，受TEA和Ba2+的抑制。拟南芥akt1突变体的AKT1内向整流通道缺陷，低钾时生长慢。K+/H+cotransportsystem毎2各H+由ATP酶运出细胞后，其中的1各又经由K+/H+同向共运转蛋白返回细胞中。High-affinityK+uptakeisanactiveprocessinvolvedionpump.总之，植物中存在几种截然不同的K+转运蛋白，它们在转运途径的不同位点起着作用。在根部，可能存在一种或几种髙亲和力K+转运蛋白，它们由H+—ATP酶提供能量，以K+/H+同向共运转的形式发挥功能。同样，也可能存在一种或几种K+通道，介导着低亲和力的K+吸收。2.3ManyplantgenesencodeK+transportersKAT1andAKT1werethefirstK+transportergenetobeclonedbycomplementationoftheyeastK+transport-detectivemutanttrk1trk2withanArabidopsiscDNAlibrary.半乳糖KAT1andAKT1showsthecharacteristicsofinwardcurrent(K+influx),selectivityfor,time-dependentkinetics,lackofinactivation,andresponsetotheTEA.Current-voltagerelationshipforuninjectedandinjectedXenopusoocyteswithKAT1mRNA4d.KAT1和马铃薯中的同源基因KST1位于叶片保卫细胞中，推测它们编码的是参与气孔作用的K＋进通道。AKT1位于根表皮和（芽孢）皮层中。AKT2在叶子中表达。KAT1在拟南芥幼苗的保卫细胞、成熟的根、侧根和排水器中表达。Shaker钾通道的结构，侧面图（左）和俯视图（右）2.5ThestructureoftransportersanditsfunctionAKT1Ahighlyconservedtripeptide(Gly-Tyr-Gly)wasfoundinP-domainsofallhighlyselectiveK+channels.AhighlyconservedThr-X-Gly-Tyr-Gly-AspmotifwasfoundinP-domainsoftheK+outchannelgene:KCO1.ThefirstK+outchannelgeneclonedfromArabidopsisbysearchinganESTdatabase.KCO1-activatedK+currentswereinfluencedstronglybytheconcentrationofcytosolicCa2+(>150nM)EFhand:Ca2+--bindingmotifsIndicatingalinkbetweenCa2+-mediatedsignalingprocessesandK+transportbythechannel.-bindingmotifsKCO1isexpressedinlowamountsinArabdopsisandisnotlocalizedtoanyparticulartissue,beingfoundinwholeseedlings,leaves,andflowers.通过酶消化，特异性地将原生质体从木质部导管周围的木薄壁组织种释放出来，利用膜片钳技术研究确定3种类型的离子通道：

K＋进通道和另外两种通道——一种对K＋有选择性，另一种无选择性。2.6Thecloningofhigh-affinityK+transportersThefirsthigh-affinityK+transporter,HKT1,wasclonedbycomplementationofyeasttrk1trk2K+transportmutantwithacDNAlibraryamassof59kDaandcontain12membrane-spanningdomainsExpressionofHKT1inXenopusoocytesgaverisetolargeinwardcurrentsinthepresentofK+.ExpressionofHKT1inyeastshowsKm=29µMExpressionofHKT1inplantislocalizedtorootcortex,steleandleaves,butnotinrootepidermis.TheexpressionofHKT1wasproposedtobeaK+-Na+cotransporterthatmediateshigh-affinityK+uptake.controlHKT1HKT1controlTheexpressionofHKT1inyeastyieldedNa+-stimulatedRb+uptake(A),andK+-stimul