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Chapter20FruitsandVegetables周海璐Fruits,vegetables,andotherplanttissueseitherdirectlyorindirectlysupplyallfoodstohumans.Anestimated（估计）270,000plantspeciesexist.Thenumberofcrops（作物）thatfitintohumans’dietary（饮食）pictureisprobablybetween1,000and2,000species.Fruitsandvegetablestakeinawidevarietyofedible（可食用的）plantparts.Fruitsaregenerallythefruitofaplantbutvegetablesincludefruits,leaves,flowers,seeds,stems（茎）,bulbs（球茎）,tubers（块茎）androotsofaplant.Leafyvegetablesaregenerallyhighinwaterandlowincarbohydrates,protein,andfats.Theyfrequentlycontainthemechanismforphotosynthesis（光合作用机制）.Someexamplesincludespinach（菠菜）,lettuce（生菜）,mustardgreens（芥末菜）,andcabbage（甘蓝）.Seedsvaryinwatercontentandareasourceofcarbohydratesandprotein.Theymaybe“fresh”andhighinwateror“dried”andrelativelylowinwatercontent.Cornandbeansareexamples.GeneralPropertiesandStructuralFeatures各类蔬菜普遍特性及结构特点Tubers（块茎）aregenerallyhigherincarbohydratesandlowerinwatercontentthanstem,flower,orleafyvegetables.Tubersareenlargedundergroundstems.Potatoesarethebestexample.Stems（茎）areplantportionsgenerallyhighinwaterandfiber.Theyhaverelativelylittleothernutritionvalue.Asparagus（芦笋）isanexample.Bulbs（球茎）aregenerallyhigherincarbohydratesandlowerinwatercontentthanstems,flower,orleafyvegetables.Bulbslikeonionsandgarlic（大蒜）areenlargementsabovetheroots.Rootslikecarrotsaregenerallyhigherincarbohydratesandlowerinwatercontentthanstem,flower,orleafyvegetables.Rootsarethepartofaplantthatgrowdownward（向下）intothesoiltoanchor（固定）theplantandfurnishnourishment（提供营养）byabsorbingnutrients.GeneralComposition一般组成Freshaswellascannedandfrozenfruitsandvegetablesprovideavarietyofvitamins,minerals,andfiber.Theyarelowinfat(exceptavocados（鳄梨）)andsodium（钠）,andtheyprovidedietaryfiber（膳食纤维）.Whole,unpeeled（未去皮的）fruitishigherinfiberthanpeeled（去皮的）fruitorfruitjuice.TableA-8(P573)providesthecompositionofmanyfruitsandvegetables.Freshandcannedfruitsandvegetablescontainahighwatercontent.Obviously,theenergycontentincreaseswhenthefruitisdried.Thecarbohydratecontentishighcomparedtotheproteincontentinfruit.Vegetablenutrientcontentvarieswidely.Somefreshandcannedvegetableshaveahighwatercontentwithsomeproteinbutmorecarbohydrate.Seedsthatareconsideredvegetablescontainhighamountsofenergy,protein,andcarbohydrates.FreshVegetableLabels新鲜蔬菜标签Underfederal（联邦）guidelinesretailers（零售商）mustprovidenutritioninformationforthe20mostfrequentlyeatenraw（生的）vegetables:potatoes,iceberglettuce（卷心菜）,tomatoes,onions,carrots,celery（芹菜）,sweetcorn,broccoli（西兰花）,greencabbage（甘蓝）,cucumbers,bellpeppers（青椒）,cauliflower（菜花）,leaflettuce（生菜）,sweetpotatoes,mushrooms,greenonions,green(snap)beans（青豆）,radishes（萝卜）,summersquash（西葫芦）,andasparagus（芦笋）.FreshFruitLabels新鲜水果标签Underfederal（联邦）guidelinesretailers（零售商）mustprovidenutritioninformationforthe20mostfrequentlyeatenrawfruits:bananas,apples,watermelons,oranges,cantaloupes（哈密瓜）,grapes,grapefruit（柚子）,strawberries,peaches,pears,nectarines（油桃）,honeydewmelons（甜瓜）,plums（李子）,avocados（鳄梨）,lemons,pineapples,tangerines（柑橘）,sweetcherries,kiwifruit（猕猴桃）,andlimes（酸橙）.Informationaboutothervegetablesorfruitsmayalsobeprovided.Thenutritionalinformationmayappearonposters,brochures（小册子）,leaflets（宣传单）,orstickers（贴纸）nearthevegetableorfruitdisplay（显示器）.Itmayincludeservingsize;caloriesperserving;amountofprotein,totalcarbohydrates,totalfat,andsodium（钠）perserving;andpercentoftheU.S.RecommendedDailyAllowances（美国每日推荐摄入量）foriron,calcium（钙）,andvitaminsAandCperserving.ActivitiesofLivingSystem生命系统的活动Becausesomanypartsofplantsareeatenforvegetablesorforfruits,anunderstandingoftheplantcellandplanttissuesisessentialtofoodscientists.Plantcellstructuredependsupontheroleandfunctionofthecell.Thecellwall（细胞壁）consistsofaprimarywall（初生壁）andasecondarywall（二次壁）.Theprimarywallsoftwocellsarejoinedtogetherbyacommonlayercalledthemiddlelamella（中间层）.Thecellwallandmiddlelamella’schiefcomponentsarecellulose（纤维素）,hemicellulose（半纤维素）,andpecticsubstances（果胶物质）.Avacuole（液泡）iscontainedwithinplantcells.Itssizedependsonthecell’sfunction.Thevacuoleiscomposedofwaterwithsolublesubstancesdissolvedwithinit.Thesemayincludesugars,acids,volatileesters（挥发性酯类）,aldehydes（醛）,ketones（酮）,andwater-solublepigmentsdependingupontheparticularfruitorvegetable.Energyconversion（能量转换）inthecelliscarriedoutbythechloroplasts（叶绿体）andmitochondria（线粒体）.Theleucoplasts（白色体：质体的一种，不含色素，多存在于植物的分生组织和储藏组织中，分布在植物体内不见光的部位，具有储藏淀粉、蛋白质和油脂的功能。）storestarchthatisusedforenergy.Themitochondriaaresmallspheres（球状）,rods（棒状）,orfilaments（丝状）thatproduceenergyforthecellthroughcellularrespiration（细胞呼吸作用）.Theycontainfats,proteins,andenzymes（酶）.Thenucleus（细胞核）ofthecellisimbedded（嵌入）withinthecytoplasm（细胞质）.Itcontrolsreproduction（复制）andproteinsynthesis（蛋白质合成）.Boththenucleusandmitochondriaareneededforthecontinuedlifeofthecell.PlantTissues植物组织Fourmaintypesofplanttissuesexistinfruitsandvegetablesarethedermal（表皮层）(epidermisandendodermis（表皮和内皮）),vascular（管道）(xylemandphloera（木质层和韧皮层）),supporting,andstoragetissue(cortex（树皮、果皮）).Thedermaltissuegenerallyisalayerofprotectivetissue.Ithasthestoma（气孔）thatwillpenetratetotheinterior（渗透到内