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Lesson 2The Classification of Horticultural PlantsObjectives of todays lecturenLearn some common terms used to group plantsnLearn the scientific protocols used to name plants so they can be universally recognizednLearn about the terminology used to distinguish plants within a speciesCategorizing plants is an ancient practicenThe Greek philosopher Theophrastus(377-288 B.C.)published the first horticulture text book“Historia Plantarum”.In this text,plants are grouped together based on life span,growth habit,retention of leaves,and other traitsnMany of these characteristics are still used to classify plantsCategorizing plantsnThousands of plants are used today in various areas of horticulturenConvenient to group plants together based on common characteristicsnLife cyclenGrowth habitnEnvironmental adaptationnEnd use or functionClassification based on life cyclenAnnuals nPlants that complete their life cycle(from seed to seed)in 1 year,e.g.(=exempli gratia)petunia,peaspetuniaPea flowernBiennials nPlants that require all or part of two growing seasons;vegetative growth in the first year,followed by overwintering(low temperature);biennials flower in the second growing season,e.g.hollyhocks,carrotClassification based on life cycleHollyhocks 蜀葵Carrot nperennials nPlants that persist for more than two seasons and do not die after flowering,e.g.maple,forsythia,tulips,daylilyClassification based on life cycleMaple Forsythia tulipsDaylily nNote that many biennials and perennials are grown as annualsnRoot crops such as carrots and beets are grown and harvested in one season before they flowernTomatoes and poinsettias are grown in the US as annuals,but in S.America they grow as perennialsClassification based on life cyclePoinsettias Classification based on growth habitNormally applied to perennial plantsnWoody plantsnHave persistent vegetative structure,e.g.trees and shrubsHerbaceous perennialsnDo not have woody structure and vegetation does not persist,e.g.daylily,hostaClassification based on growth habitVines nClimbing or trailing plants that require support,e.g.grapes,wisteria(柴藤),clematis(铁线莲)Classification based on growth habitClassification based on growth habitnDeciduous plantsnShed leaves for part of the yearnEvergreensnNever without leavesnThey still shed leaves or needles after new organs are formedntemperaturenHardy,tolerant of low temperaturesnTender,unable to survive low temperaturesnWarm season crops,e.g.corn,beans,melonnCool season crops,e.g.lettuce,peas,broccoliClassification based on environmental adaptationnRequirement for waternAquatic plants,which live in waternXerophytes,which require very little waternSoil conditionsnHalophytes are adapted to salty conditionsnAcidophytes require acid soils,e.g.rhododendronsnMetallophytes require high levels of specific metalsClassification based on environmental adaptationClassification based on usagenEdible plantsnFruits(dessert or snack)nVegetables(savory)nNote that this classification differs from the botanical definition of a fruit.The strict botanical definition of a fruit is a structure that develops from the ovary in a flower.Using this definition,a tomato is a fruit while a strawberry is not.Yew Classification based on usagenOther culinary uses include:nNuts(hard seeded fruits)nHerbs(fresh or dried vegetative tissue)nSpices(dried fruit or bark)nBeverages(tea and coffee)nMedicinal plantsnSource of pharmaceuticals,e.g.digitalis(洋地黄)from foxglove(毛地黄),taxol(紫杉酚)from a yewFoxglove Classification based on usagenIndustrial plantsnProvide raw materials for industrial use nOils from oil palm or jojobanFibers from flax or hempJojoba Palm Flax Hemp Classification based on usageIvy fruitsPachysandra terminalisPansy Chrysanthemum Roses nOrnamental usesnNursery crops,e.g.trees and shrubsnGround covers,e.g.ivy and pachysandranBedding plants,petunias and pansiesnFoliage plants,for indoor decorationnPot crops,e.g.poinsettia and chrysanthemumnFloriculture crops,e.g.roses and carnationsLimitations of these classification systemsnClassifications are very subjectivenBased on your perspective,a hazel(榛树)shrub can be regarded as a source of nuts,an ornamental landscape shrub,or a weed.nWhat is grown as an annual in one region is classified as a perennial elsewherenPlants that are considered hardy in Florida or Georgia are considered tender in Indiana.Limitations of these classification systemsnThese classifications are not understood throughout the world,in different languages or across culturesnCommon names can be confusingnSame name used to describe different plantsnDifferent names to describe the sameScientific classification systemAdvantage of this system include:nCommon universal designationnBased on international conventionnUses Latin,a“dead”language that will not changeAll organisms are divided into a series of categories called“taxa”Scientific classification systemKingdom(plant,animal,bacteria,etc)Division Class Order Family Genus SpeciesnMembers of each successive category are more similar to each otherScientific classification systemnDeveloped by Carl von Linne,a Swedish physician.He is better known as Linnaeus,the father of taxonomynIn 1975,“Species Plantarum”was published,which described his new classification systemScientific classification systemnLinnaeus system of classification is based on stable morphological features,especially flowersnAvoids features that can vary with age of the plant or the environment in which the plant is grownnIncorporates the concept of evolution,i.e.(id est)plants with similar features share a common ancestorThe binomial systemnEach name has two components:Genus+specific epithet=species Prunus persica(peach)nBelongs to the Genus PrunusnSpecies name is Prunus persica nConventions that apply to this system:nWritten in italics(or underlined)nFirst letter of the Genus is capitalizedThe binomial systemnGenus a group of similar organisms,some of which may interbreednSpecies-Members will interbreed and produce similar progenyNo matter your origin or situation,solanum tuberosum is recognized as referring to pomme de terre,kartoffel,potatoThe binomial systemnAvoids confusion that can arise when using common namesHypericum calycinum Rose of SharonRose of SharonHibiscus SyriacusAdditional terms used with the binomialn Prunus persica(L.)Batsch n(L.)indicates the“authority”,the individual who first named this speciesnLinnaeus is indicated by(L.)nOthers are written out in fullnAmendments to the classification are added after the authority,e.g.BatschAdditional terms used with the binomialnBotanical varieties Juniperus communis var.depressanIndicates a botanical variety within this species of juniper,in this case plants with a distinctive low-growing(depressed)habitAdditional terms used with the binomialnInterspecific hybrids Forsythia X intermedian“X”Indicates these plants result from a cross between two different species(F.suspensa and F.viridissima)in the genus ForsythiaForsythia X intermediaF.viridissimaF.suspensa XAdditional terms used with the binomialn Prunus persica cv.Redhaven ncv.Redhaven indicates a cultivarnAlso written as Prunus persica Redhaven nSingle quotation marks indicates the cultivarnCultivars are cultivated varietiesnCultivars that share common characteristics and maintain their identitySummary n many different methods used to classify plants used in horticulturenThe scientific binomial system provides a universal protocol that does not depend on variable factors
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