专业外语植病部分准确.docx
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专业外语植病部分准确.docx
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专业外语植病部分准确
CHAPTER1,INTRODUCTIONTOPLANTPATHOLOGY
Thewelfareofplantsisofparticularinteresttothosemostdirectlyconcernedwiththegrowthofplantsandthemanufactureanddistributionofplantproducts.Suchpersonsincludenotonlyfarmersandworkersinindustriesthatprocessagriculturalproductsbutalsoinnumerableworkersinsupportingindustries,whoselivelihooddependsonmakingequipmentorproductsusedinprocessingplantproducts-forexamples,machineryfortextileandcanningindustries-orondistributingtherawormanufacturedagriculturalproducts.Mostimportantly,however,thewelfareofplantsshouldbeofconcerntoeveryoneofusasgrowersofplantsforfoodorpleasure,asindividualsconcernedwiththebeautyandsafetyofournaturalenvironment,andparticularly,asconsumersofplantsandoftheendlessseriesofproductsderivedfromplants.
Thegrowthandyieldofplantsdependontheavailabilityofnutrientsandwaterinthesoilwheretheygrowandonthemaintenancewithincertainrangesofsuchenvironmentalfactorsastemperature,.moisture,andlight.Anythingthataffectsthehealthbfplantsislikelytoaffecttheirgrowthandyieldandmay,seriouslyreducetheirusefulnesstohumans.Plantpathogens,unfavorableweather,weeds,andinsectpestsarethemostcommoncausesofreductionordestructionofplantgrowthandproduction.Plantssufferfromdiseasewhosecausesaresimilartothoseaffectinganimalsandhumans.Althoughwehavenoevidencethatplantsfeelpainordiscomfort,thedevelopmentofdiseasefollowsthesamestepsandisusuallyascomplexinplantsasitisinanimals.
Plantpathologyisthestudyof
(1)thelivingentitiesandtheenvironmentalconditionsthatcausediseaseinplants;
(2)themechanismsbywhichthesefactorsproducediseaseinplants;(3)theinteractionsbetweenthediseasecausingagentsandthediseasedplant;and(4)themethodsofpreventingorcontrollingdiseaseandalleviatingthedamageitcauses.
Plantpathologiststudydiseasescausedbyfungi,bacteria,mycoplasmas,parasitichigherplants,viruses,viroids,nematodes,andprotozoa.Theyalsostudyplantdisorderscausedbytheexcess,imbalance,orlackofsuchphysicalorchemicalfactorsasmoisture,temperature,andnutrients.Plantdamagecausedbyinsects,humans,orotheranimalsisnotordinarilyincludedinthestudyofplantpathology.
Plantpathologyusesthebasicknowledgeandtechniquesofbotany,mycologybacteriology,virology,nematology,plantanatomy,plantphysiologygenetics,molecularbiology,geneticengineering,biochemistry,horticulture,tissueculture,soilscience,forestry,chemistry,physics,meteorology,andmanyotherbranchesofscience.Plantpathologyprofitsfromadvancesinanyoneofthesesciences,andmanyadvancesinotherscienceshavebeenmadeinanattempttosolveplantproblems.Aknowledgeoratleastthebasicfactsoftherelatedsciencesisindispensablefortheefficientperformanceofanyplantpathologist.
Asascience,plantpathologyattemptstoincreaseourknowledgeofthecausesandthedevelopmentofplantdiseases.Itisalsoasciencewithamorepracticalgoal:
todevelopcontrolsforallplantdiseasesinordertosavetheproducethattodayisdestroyedbyplantdiseasesandtomakeitavailabletothehungryandill-clothedmillionsofourincreasinglyoverpopulatedworld.
SECTION1TheConceptofDiseaseinPlants
Aplantishealthyornormalwhenitcancarryoutitsphysiologicalfunctionstothebestofitsgeneticpotential.Thesefunctionsincludenormalcelldivision,differentiation,anddevelopment;absorptionofwaterandmineralsfromthesoilandtranslocationofthesesubstancesthroughouttheplant;photosynthesisandtranslocationofthephotosyntheticproductstoareasofutilizationorstorage;metabolismofsynthesizedcompounds;reproduction;andstorageoffoodsuppliesforoverwinteringorreproduction.
Wheneverplantsaredisturbedbypathogensorcertainenvironmentalconditionsandoneormoreofthesefunctionsisinterferedwithbeyondacertaindeviationfromthenormal,thentheplantsbecomediseased.Theprimarycausesofdiseaseareeitherpathogeniclivingorganisms(pathogens)orfactorsinthephysicalenvironment.Thespecificmechanismsbywhichdiseasesareproducedvaryconsiderablywiththecausalagentandsometimeswiththeplant.Atfirsttheplantreactstothedisease-causingagentatthesiteofaffliction.Thereaction,ofachemicalnature,isinvisible.Soon,however,thereactionbecomesmorewidespread,andhistologicalchangestakeplacethatmanifest-themselvesmacroscopicallyandconstitutethesymptomsofthedisease.
Affectedcellsandtissuesofdiseasedplantsareusuallyweakenedordestroyedbydisease-causingagents.Theabilityofsuchcellsandtissuestoperformtheirnormalphysiologicalfunctionsisreducedorcompletelyeliminated;asaresult;plantgrowthisreducedorplantdies.Thekindsofcellsandtissuesthatbecomeinfecteddeterminethetypeofphysiologicalfunctionthatwillbe-affectedfirstThus,infectionoftheroot(forexample,rootrots)interfereswithabsorptionofwaterandnutrientsfromthesoil;infectionofthexylemvessels(vascularwilts,certaincankers)interfereswithtranslocationofwaterandmineralstothecrownoftheplant;infectionofthefoliage(leafspots,blight,mosaics)interferewithphotosynthesis;infectionofthecortex(corticalcanker,viralandmycoplasmalinfectionsofphloem)interfereswiththe:
downward,translocationofphotosyntheticproducts;flowerinfectionsof(bacterialandfungalblights,viral,mycoplasmal,andfungalinfectionsofflowers)interferewithreproduction;andinfectionsoffruit(fruitrots)interferewithreproductionorstorageofreservefoodsforthenewplant.
Incontrast,theseisanothergroupofdiseasesinwhichtheaffectedcells,insteadofbeingweakenedordestroyed,arestimulationtodividemuchfaster(hyperplasia)ortoenlargeagreatdealmore(hypertrophy)thannormalcells.Suchhyperplasticorhypertrophiedcellsresultinthedevelopmentofusuallynonfunctioning,abnormally,large,orabnormallyproliferatingorgansorintheproductionofamorphousovergrowsonnormal-lookingorgans.Overstimulatedcellsandtissuesnotonlydivertmuchoftheavailablefoodstuffstothemselvesandawayfromthenormaltissues,butfrequently,bytheirexcessivegrowth,crushadjacentnormaltissuesandinterferewiththephysiologicalfunctionsofplant.
Inplant,then,diseasecanbedefinedasthemalfunctionofhostcellsandtissuesthatresultsfromtheircontinuousirritationbyapathogenicagentorenvironmentalfactorandleadstothedevelopmentofsymptoms.Diseaseisaconditioninvolvingabnormalchangesintheform,physiology,integrity,orbehavioroftheplant.Suchchangesmayresultinpartialimpairmentordeathoftheplantoritsparts.
Pathogensmaycausediseaseinplantsby
(1)weakeningthehostbycontinuallyabsorbingfoodfromthehostcellsfortheirownuse;
(2)killingordisturbingthemetabolismofhostcellsthroughtoxins,enzymes,orgrowth-regulating-substancetheysecrete-,(3),blockingthetransportationoffood,mineralnutrients,andwater,throughtheconductivetissues;and(4)consumingthecontentsofthehostcellsupon,contact.Diseasescausedbyenvironmental;factorsresultfromextremesintheconditionssupportinglife(temperature;moisture,light,andsoon)andinexcessive,deficientamountsofchemicalsabsorbedorrequiredbyplants.
SECTION2ClassificationofPlantDiseases
Tensofthousandsofdiseasesaffectcultivatedplants.Ontheaverage,eachkindofcropplantcanbeaffectedbyonehundredormoreplantdiseases.Eachkindofpathogenmayaffectanywherefromonevarietytoseveraldozenorevenhundredsofspeciesofplants.Tofacilitatethestudyofplantdiseases,therefore,theymustbegroupedinsomeorderlyfashion.Thisisnecessaryalsofortheidentificationandsubsequentcontrolofanygivenplantdisease.Anyoneofseveralcriteriamaybeusedtoclassifyplantdiseases.Plantdiseasesaresometimesclassifiedaccordingtothesymptomstheycause(rootrots,cankers,wilts,leafspots,scabs,blights,anthracnoses,rusts,smuts,mosaics,yellows),accordingtotheplantorgantheyaffect(rootdiseases,stemdiseases,foliagediseasesfruitdiseases),oraccordingtothetypesofplantsaffected(fieldcropdiseases,vegetablediseases,fruittreediseases,forestdiseases,turfdiseases,diseasesofornamentalplants).Themostuseful-criterionforclassificationofadisease,however,isthetypeofpathogenthatcausesthedisease.Theadvantageofwhichsuggeststheprobabledevelopmentandspreadofthediseaseandalsopossiblecontrolmeasures.Onthisbasis,plantdiseasesareclassifiedasfollows:
1.Infectious,orbiotic,plantdiseases
1.Diseasescausedbyfungi
2.Diseasescausedbyprokaryotes(bacteriaandmycoplasmas)
3.Diseasescausedbyparasitichigherplants
4.Diseasescausedbyvirusesandviroids
5.Diseasescausedbynematodes
6.Diseasescausedbyprotozoa
Ⅱ.Noninfectiousmorabiotic,diseasesarediseasescausedby:
1.Toolowortoohighatemperature6.Nutrientdeficiencies
2.Iackorexcessofsoilmoisture7.Mineraltoxicities
3.lackorexcessoflight8.Soilacidityoralkalinity(pH)
4.1ackofoxygen'9.Toxicityofpesticides.
5.Airpollution10.Improperculturalpractices
SECTION3GeneticEngineeringandPlantPathology
In1944,AveryandhiscolleaguesshowedforthefirsttimethatDNAcarriesgeneticinformation.TheyconcludedthisfromexperimentsinwhichDNAfromheat-killedpathogenicpneumoniabacteria(Diplococcuspneumoniae)couldtransformnonpathogenicbacteriaintop
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