Lesson 2.ppt
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1、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 pla
2、nts 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 clas
3、sify 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
4、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.hollyhock
5、s,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
6、 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
7、 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,wisteri
8、a(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
9、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 sa
10、lty 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 b
11、otanical 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
12、 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
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