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1、Plants and Environmental FactorsLesson 3MAIN ROOTLATERALOR SIDE ROOTROOT SYSTEMLEAFSTEMFLOWERFRUITNODENODENODEINTER-NODETERMINAL BUDAXILLARYBUDSHOOTSYSTEMWhat are the structural differences between dicot and monocot stems?MonocotsOne seed leafParallel veins in leafXylem and phloem found in bundles i

2、n stemDicotsProduce two seed leavesBranched leaf vein systemXylem and phloem cells located in separate areas of the stemWhat are the functions of roots?Whitish or tan in colorMake up one-half or more of the entire plant bodyAbsorb water and nutrients from the soil then transport them above groundSer

3、ve to anchor and support the top portion on plantCan store carbohydrates to be used later for energy by plantWhat are the parts of a root system?Primary root-first structure to emerge from germinating seedSecondary root-arises from the primary rootDont transplant seedlings or cuttings until after se

4、condary root formsRoot hairs-single cell roots located a few mm back from root tip,absorb waterRoot cap-mass of cells that protects root tips from coarse soilWhat are the differences between taproot and fibrous root systems?TaprootOne large primary root that grows down+small secondary rootsFibrous r

5、ootRoot develops into a number of small primary and secondary rootsGrow shallow near the soil lineSubjected to drought and mineral deficienciesMost landscape plantsWhat are modified roots?Adventitious roots(不定根不定根)Begin growing from stem or leafGrow from cuttings after being placed in growing medium

6、 Plant attaches itself totree branch or telephone wireRoots hang down in mid-air and absorb water from rainfallBanyan tree（印度榕樹(shù)）（印度榕樹(shù)）Schefflera bonsai（鵝掌藤）（鵝掌藤）Examples:Wild Pine;Some OrchidsPROPROOTSe.g.CornSTILT（支柱）（支柱）ROOTSe.g.Mangrove紅樹(shù)紅樹(shù)Aerating root（呼吸根，通氣根）Flower Where are the reproductive s

7、tructures of plants and how do they work?Sepals-green leaf-like structures under the petalsPetals-brightly colored structures on flower used to attract pollinatorsStamens-male reproductive parts containing filament and anther surrounding female partsFilament-stalk that supports antherAnther-produces

8、 pollen or male sex cellsPistils-female reproductive parts containing stigma,style,and ovaryStigma-sticky surface for capturing pollen at top of stylesStyle-tube-like structure that connects stigma and ovaryOvary-contains ovules or eggsThe structure of flowersPollen grains How do we get seeds?Pollin

9、ation-occurs when pollen grains are transferred from anther to stigmaBy birds,insects,bats,animals,windSelf pollination-pollen pollinates flower on same plantCross pollination-pollen from flowers on one plant transfer to flowers on different plantHybrid-offspring from cross-pollinating two different

10、 varieties of a speciesFertilization-one sperm nucleus fuses with egg cell nucleusDouble fertilizationAngiosperm Life cycle from seed to seedWhat are the types of flowers?Complete flower-has all four major parts(sepals,petals,stamens,pistils)ex.Apple,lily,peaIncomplete flowers-lack one or more major

11、 partsPerfect flowers-have both stamens and pistilsImperfect flowers-lacks either stamen or pistils,ex.Corn,squashRue-anemone flowers lack petals,but the sepals are petal-like.Thalictrum thalictroides What are the two types of fruit?Fruit-seed-bearing organFleshy fruit-composed of a soft and fleshy

12、material with seed or seeds enclosedEx.Blueberry,peach,tomato,watermelonDry fruit-consists of seed enclosed in a fruit wall that is hard and brittle when matureEx.Pea,oak,elmacornWhat are the parts of a seed?Seeds-mature,fertilized eggs contained in the fruitSeed embryo-root,stem,&one or two seed le

13、aves called cotyledonsMonocots-one cotyledonDicots-two cotyledonEndosperm-contains stored food for seedSeed coat-tissue surrounding embryo and endosperm to protect seed from moisture loss,injuryDiagram of the internal structure of a dicot seed and embryo:(a)seed coat,(b)endosperm,(c)cotyledon,(d)hyp

14、ocotylThe inside of a Ginkgo seedHow do we go from seed to plant?Germination-seed embryo goes from dormant state to active growing stateSeed absorbs water and swellsPrimary root develops and emergesStem or shoot emergesPlant Growth EnvironmentClimate&plant growthClimate average weather of an areaAir

15、,Moisture,Temperature,LightRegional climate vs.microclimateAirHumidityWindAir pollutionElevation(temperature)Air and elevationMoisture and plant growthAmountDistribution patternsAccess(location)Bodies of water and climateMoisture stressDeficiency,excessGrowth responses to temperatureVernalizationPer

16、iod of low temperature induces flowering(e.g.“forcing”bulbs)ThermoperiodismSugar/starch content varies with temperature(cooler temps promote starch conversion to sugars);some plants grow better if night temperatures are cooler than day temperaturesTemperature and germinationStratificationPeriod of c

17、old required to induce germinationRequired by many types of perennials,woody speciesSpecific temp.and length of stratification varies by speciesTemperature stressLow temperature stressChillingFreezingPremature boltingCold water stressPreventing low temp.stressTiming of plantingZone rating of species

18、Protective measuresCoversMounding mulch,soilHardening(cold frame)Heat stressSunscaldPlant relocationLightIntensityQualityDaylengthPhotoperiodismGrowth responses to daylengthFlowering,germination,dormancyMediated by pigment molecule phytochromePhytochrome and floweringManipulation of photoperiodPoins

19、ettia industryChrysanthemumsWhy wont my Christmas cactus bloom?Photoperiodic houseplantsCommon nameGardenia Strawberry begoniaSpider plantBotanical namePhotoperiodic classificationRemarks Phytochrome and stem growthEtiolation occurs in low light or darkwhy?Biotic environmental factorsInsectsMicroorg

20、anismsMedia,Nutrients,and FertilizersWhy is growing media important?Growing medium-material where plants growMediaProvides nutrients by absorption through rootsAnchors plantsContains pore spaces which provide oxygen for rootsProvides favorable environment for microorganismsWhat are the different typ

21、es of growing media?SoilThin layer of earths curst that provides for growth of plantsSoilless mediumContains no topsoilUsually made of:VermiculiteHeat treated micaHolds moisturePerliteVolcanic materialProvides drainage and aerationSterilized organic compoundsLoosen the mediumCreate larger air spaces

22、 between the particlesInclude:Peat MossSphagnum MossLeaf MoldBarkHydroponics-growing plants in a nutrient solution consisting of water and dissolved nutrient saltsAdvantagesComplete control of nutrient solutionGreater yield per unit area through closer spacing of plantsLess spreading of rootsReduced

23、 need for control of weeds,disease,and insects due to absence of soilHydroponic systems are classified according to substrate systemsSubstrate systemsSand culture-plants grown in sterilized sand with individual drip irrigationGravel culture-involves irrigating plants grown in gravel for mechanical s

24、upportBag culture-uses plastic bags that are filled with substrate,such as rockwool,peat-lite,and sawdust.Drip irrigation used to supply nutrient solutionBare root systems:Aeroponic systemInvolves plant roots suspended in air with a fine mist of oxygen-rich nutrient solution sprayed on them a regula

25、r intervalsContinuous flow systemInvolves using shallow pools with panels containing plants floating on the surfaceNutrient film technique(NFT)Involves using a recirculating,shallow stream of nutrient solution that moves through channels in which the plants grow.The roots are usually covered with a

26、plastic sheetWhat are the contents of soil?Mineral matterFormed from inorganic sources,such as rocks and mineralsOrganic matterDecayed or partially decayed plant and animal matter;high in nutrientsWaterAirKinds of mineral matterSandLarge particleAssists in drainage but may not hold enough moisture f

27、or plantsSilt(泥沙泥沙)Medium-sized particlePreferred mineral component in most situationsClay(粘土粘土)Smallest particleHolds water and keeps soil moistMay be too slow to dry and may be too compactWhat is the structure of soil?Soil textureCoarseness or fineness of soil particlesAffect many properties of th

28、e soil and its usefulnessMedium-textured soil is most preferredSoil structurePhysical arrangement of soil particlesContributes to aeration or the movement of air into the soilSoil profileVertical cross-section of the soil at a particular locationMakes visible the different layers of soil referred to

29、 as horizonsO horizon-Organic matter:Litter layer of plant residues in relatively undecomposed form,2”.A horizon-topsoil;humus,roots,organisms,10”B horizon-subsoil;fine particles,leached materials,some roots,30”C horizon-parent material;weathered bedrock and some leached materials,48”R horizon-bedro

30、ck;underlying solid rock What are the nutrients needed for plant growth?MacronutrientsMicronutrientsMacronutrientsPrimary-nutrients needed in large amountsN-nitrogenP-phosphorusK-PotassiumSecondary-nutrients needed in small amountsCa-calciumMg-MagnesiumS-sulfurMicronutrientsNutrients needed in very

31、small amountsB-boronCu-copperCl-chlorineFe-ironMn-ManganeseMo-MolybdenumZn-ZincSoil testUsed to determine which nutrients are present in the soil and to what degreeImportant to determine the availability of nutrientsShows you what nutrients are deficient and the kinds and amounts of fertilizer neede

32、d to replenish the nutrients Primary NutrientsNitrogenDetermines greenness color and density in plantNeeded for chlorophyll,which is needed for photosynthesisImproves plants ability to resist disease and tolerate effects of heat,cold,and droughtDeficiency symptom:yellowing of leaves called chlorosis

33、PhosphorusHelps plants hold and transfer energy for metabolismAffects cell division,root development,and floweringDeficiency symptom:purple coloring of leaves or stemsPotassiumActivates enzymesRegulates opening and closing of stomataRegulates water uptake by root cellsDeficiency symptom:brown scorch

34、ing and curling of leaf tips as well as chlorosis(yellowing)between leaf veins;Purple spots may also appear on the leaf undersides.What is pH?pH-measure of amount of alkalinity or acidity in soilpH scale1 to 141 is extremely acidic14 is extremely alkaline7 is neutralpH affects the availability of nu

35、trients to plantsHow is pH modified?pH can be lowered or elevated depending on present conditions of the soil and the pH requirements of the plant cropTo lower pH-add sulfurTo increase pH-add limestoneMost plants require a pH of 5.5 to 8.0What is fertilization and fertilizer?Fertilizer-any material

36、used to provide nutrients plants needFertilization-cultural practice of adding plant nutrients to the soil or other growing mediaFertilizersComplete fertilizers-those containing all three primary nutrients(N,P,K)Incomplete fertilizers-lacks one or more primary nutrientsActive ingredient-total percen

37、tage of nutrients being appliedInert ingredient-carrier of filler ingredientFertilizer AnalysisThe composition of active ingredients in a fertilizer formulationA fertilizer with an analysis of 16-4-8 has an analysis of:16%Nitrogen4%Phosphate8%Potash72%Inert materialWhat is the association between so

38、ils and nutrients?LeachingDownward pulling of nutrients through the soil by percolating water(滲濾水)Available nitrogenAffected by pH and amount and form of nitrogen presentN is lost by leaching,removal of plat material,gaseous loss by volatilization of ammonia,and denitrification(脫硝作用)Available phosph

39、orusAffected by pH and generally immobile in soilMay be tied up in insoluble formsAvailable potassiumAffected by pH and is readily soluble in waterLeaching losses can be high in sandy soilsHow is fertilizer used?Apply fertilizer so that you dont waste itApply fertilizer when the plants can best use

40、the nutrientsApply small amounts of fertilizer frequentlyBe careful not to over fertilizeForms of FertilizerLiquidApply with a sprayerGranularApply with a spreaderFertigationApplication of fertilizers through an irrigation systemQuestions What are the structural differences between dicot and monocot

41、 stems?What are the differences between taproot and fibrous root systems?Where are the reproductive structures of plants and how do they work?What are the two types of fruits?What is Vernalization and Photoperiodism?QuestionsWhat are the different types of growing media?What are the contents and structure of soil?What nutrients are needed for plant growth?What is pH and how is it modified?What is fertilization and fertilizer?What is the association between soils and nutrients?