unit 6: vegetative growth and plant propagation chapters 15 &16

Unit 6: Vegetative Growth Unit 6: Vegetative Growth and Plant Propagationand Plant Propagation

Chapters 15 &16Chapters 15 &16

Unit 6: Vegetative Growth and Unit 6: Vegetative Growth and Plant PropagationPlant Propagation

Unit 6 ObjectivesUnit 6 Objectives Understand how stems, leaves, and roots Understand how stems, leaves, and roots

grow, and the coordinated efforts of the plant grow, and the coordinated efforts of the plant to make this happento make this happen

Stages of development, and factors affecting Stages of development, and factors affecting plant growthplant growth

Discuss seed germinationDiscuss seed germination Understand sexual vs. asexual reproduction, Understand sexual vs. asexual reproduction,

and self-fertilization vs. cross-fertilizationand self-fertilization vs. cross-fertilization


GrowthGrowth Increase in volume and wt.Increase in volume and wt. Increase cell numbers and sizeIncrease cell numbers and size Primary GrowthPrimary Growth

Occurs in young, herbaceous organsOccurs in young, herbaceous organsIncreases length of shoots and rootsIncreases length of shoots and rootsMonocots and herbaceous dicotsMonocots and herbaceous dicots

Secondary GrowthSecondary GrowthIncreased girthIncreased girthLayers of woody tissueLayers of woody tissue


Occurs at the apical meristemOccurs at the apical meristem

Seed GerminationSeed Germination Life in a seed is virtually undetectableLife in a seed is virtually undetectable Seed will die if it is not allowed to germinateSeed will die if it is not allowed to germinate Time to germination varies with speciesTime to germination varies with species Six steps to germinationSix steps to germination

Water presenceWater presence

Enzyme activationEnzyme activation

Hydrolysis & catabolism of storage compoundsHydrolysis & catabolism of storage compounds


Initiation of embryo growthInitiation of embryo growth

Anabolism and formation of new cell structuresAnabolism and formation of new cell structures

EmergenceEmergence 4 environmental factors affecting germination4 environmental factors affecting germination

WaterWater Absorption of water is first step in germinationAbsorption of water is first step in germination A sufficient amount of available water must be present at A sufficient amount of available water must be present at

germination, and must continue to be present after germination, and must continue to be present after growth beginsgrowth begins

Medium for transport, activates enzymes that initiate Medium for transport, activates enzymes that initiate metabolic function, metabolic function,


LightLight Can stimulate or inhibit germination, depending on the Can stimulate or inhibit germination, depending on the

speciesspecies

OxygenOxygen Respiration is taking place in all viable seedRespiration is taking place in all viable seed Medium where seed is placed should be loose enough Medium where seed is placed should be loose enough

for oxygen to permeate through the soilfor oxygen to permeate through the soil Reduced oxygen supply can reduce or inhibit Reduced oxygen supply can reduce or inhibit

germinationgermination

HeatHeat Affects the rate and percentage of germinationAffects the rate and percentage of germination Temperature needs for germination also vary w/ speciesTemperature needs for germination also vary w/ species Usually 65-75Usually 65-75º is optimal for most plantsº is optimal for most plants


Germination begins when:Germination begins when: Mature embryo in the seedMature embryo in the seed Large enough endosperm to sustain growthLarge enough endosperm to sustain growth Sufficient growth regulators to initiate the processSufficient growth regulators to initiate the process

Seeds Lacking True DormancySeeds Lacking True Dormancy Common vegetable seedsCommon vegetable seeds Ready to sprout after plantingReady to sprout after planting All they need is proper moisture and temperatureAll they need is proper moisture and temperature

Seeds w/ True Dormant EmbryosSeeds w/ True Dormant Embryos Thick seed coatThick seed coat

Restricts water access to the seedRestricts water access to the seedScarification – allows thick coated seeds to Scarification – allows thick coated seeds to germinate, usually occurs naturally (How?)germinate, usually occurs naturally (How?)


Thin Seed CoatThin Seed CoatNo barrier to waterNo barrier to waterDormancy is controlled by another factor (light)Dormancy is controlled by another factor (light)

Insufficient DevelopmentInsufficient DevelopmentEmbryo may have to fully mature before germination Embryo may have to fully mature before germination can occurcan occurEmbryo often has to feed on something else to foster Embryo often has to feed on something else to foster germinationgerminationUsually not viable for long periods of timeUsually not viable for long periods of time

InhibitorsInhibitorsChemical factors that inhibit germinationChemical factors that inhibit germinationSeed must eliminate these chemicals for germination Seed must eliminate these chemicals for germination to occurto occur


Abscisic Acid – compound present that restricts a Abscisic Acid – compound present that restricts a seed from germinating through winter, seed spends seed from germinating through winter, seed spends entire winter breaking down the acidentire winter breaking down the acidPhenolic Compounds – protect seed until proper Phenolic Compounds – protect seed until proper moisture is present for germination – common in dry moisture is present for germination – common in dry regionsregions

The Germination Process of CornThe Germination Process of CornKernel absorbs waterKernel absorbs waterSeed swells as chemical processes begin to Seed swells as chemical processes begin to prepare for growthprepare for growthActivation of enzymes to break down food reserves Activation of enzymes to break down food reserves needed for growthneeded for growthEndosperm starch is converted to sugarsEndosperm starch is converted to sugars


Radicle elongates and breaks through the seed Radicle elongates and breaks through the seed coatcoat

Grows in the direction the kernel is pointed (except up)Grows in the direction the kernel is pointed (except up)

Coleoptile emerges from the seedColeoptile emerges from the seed2-5 seminal roots emerge2-5 seminal roots emergeCan occur in 4-5d under optimal conditionsCan occur in 4-5d under optimal conditionsCrown area found 1-1.5” beneath soil surfaceCrown area found 1-1.5” beneath soil surface

Permanent roots developPermanent roots develop If seed is planted deeper the mesocotyl is responsible for If seed is planted deeper the mesocotyl is responsible for

pushing coleoptile through the soil surfacepushing coleoptile through the soil surface

First leaves emerge from the coleoptile after it First leaves emerge from the coleoptile after it emergesemerges


Time from planting to emergence is most affected Time from planting to emergence is most affected by temperatureby temperature

1 wk. under optimal conditions1 wk. under optimal conditions May be 2-3 wks in cool conditionsMay be 2-3 wks in cool conditions

What other factors can influence emergence?What other factors can influence emergence? The SeedlingThe Seedling

11stst leaf blade has a rounded tip leaf blade has a rounded tipLeaves begin photosynthesis and the plant no Leaves begin photosynthesis and the plant no longer depends on the seed for survivallonger depends on the seed for survivalCrown root system begins to take control from the Crown root system begins to take control from the seed rootsseed roots


Apical meristem initiates new leaf formationApical meristem initiates new leaf formation Point is below ground until the internodes elongatePoint is below ground until the internodes elongate Aboveground leaves can be destroyed, and additional Aboveground leaves can be destroyed, and additional

leaves can still formleaves can still form

Unless disease occursUnless disease occurs

Hypogeal emergenceHypogeal emergence Growing point remains beneath soil surface for a period Growing point remains beneath soil surface for a period

of time after emergenceof time after emergence

Epigeal emergenceEpigeal emergence Growing point is above soil surface at the time of Growing point is above soil surface at the time of

emergenceemergence


RootsRoots 4 functions4 functions

AnchorAnchor

Absorb water and nutrientsAbsorb water and nutrients

Conduct water and nutrientsConduct water and nutrients

Store food materialsStore food materials Root and shoot system tends to stay Root and shoot system tends to stay

balanced to meet plant needsbalanced to meet plant needs


Shoot GrowthShoot Growth Determinate growthDeterminate growth

Flowering occurs after a certain period of Flowering occurs after a certain period of vegetative growthvegetative growthMost shoot elongation stopsMost shoot elongation stopsCommon in vegetablesCommon in vegetables

Indeterminate growthIndeterminate growthFlower clusters form laterally along the stemFlower clusters form laterally along the stemShoots remain actively growing until stopped by Shoots remain actively growing until stopped by senescence or something elsesenescence or something else

Ex. grapevinesEx. grapevines


Growth PatternsGrowth Patterns3 classifications:3 classifications:

AnnualsAnnualsComplete life cycle in less than 1 yr.Complete life cycle in less than 1 yr.Shoot growth in continual until senescenceShoot growth in continual until senescenceFlowering, fruit, and seed production occurs in the Flowering, fruit, and seed production occurs in the summersummerHerbaceousHerbaceous

BiennialsBiennialsLife cycle in two growing seasons, longer than 1 yr Life cycle in two growing seasons, longer than 1 yr but not necessarily 2 yrsbut not necessarily 2 yrsStored energy from 1Stored energy from 1stst yr used in reproduction in 2 yr used in reproduction in 2ndnd yryr


Ex. Celery, asparagus, sugar beetsEx. Celery, asparagus, sugar beetsLimited stem growth in first seasonLimited stem growth in first seasonDormant winter periodDormant winter periodFlowering, fruit, and seed production during second Flowering, fruit, and seed production during second seasonseasonSenescence and death follow soon after productionSenescence and death follow soon after productionHerbaceousHerbaceous

PerennialsPerennialsContinue growth for 2+ yrsContinue growth for 2+ yrsVegetative growth during and after reproductive Vegetative growth during and after reproductive phasephaseEx. Bermuda grass, shrubs, treesEx. Bermuda grass, shrubs, treesShoot growth resumes each springShoot growth resumes each springHerbaceous or woodyHerbaceous or woody


Phase ChangesPhase Changes JuvenilityJuvenility

Plant may have a different appearancePlant may have a different appearance

Inability to form flowers during this phaseInability to form flowers during this phase

Length varies from days to yearsLength varies from days to years Most crops vary amount of daysMost crops vary amount of days Trees can have 30-40 yr juvenile stagesTrees can have 30-40 yr juvenile stages

MaturityMaturityAble to produce flowers, fruit, and seedsAble to produce flowers, fruit, and seeds

May have different appearanceMay have different appearance

May last days to yearsMay last days to years


FloweringFlowering Days to flowering varies w/ speciesDays to flowering varies w/ species Can be induced by environmental controlsCan be induced by environmental controls Pollination and fertilization followPollination and fertilization follow

Senescence & DeathSenescence & DeathTerminal, irreversible deteriorating changeTerminal, irreversible deteriorating change

Results in cell breakdown and deathResults in cell breakdown and death

Obvious period of physical declineObvious period of physical declineCan also occur in leaves, seeds, flowers, or fruitsCan also occur in leaves, seeds, flowers, or fruitsExhibited in different waysExhibited in different ways

Total plant deathTotal plant death Top plant deathTop plant death


Usually a natural occurrence, but can be induced Usually a natural occurrence, but can be induced by disease or stressby disease or stress

Can be postponed by removing dead flowersCan be postponed by removing dead flowers

AbscissionAbscission Losing leaves or fruitLosing leaves or fruit Involves abscisic acidInvolves abscisic acid

FruitsFruits Maturation process of fruitMaturation process of fruit Should be picked at ripening to prevent senescenceShould be picked at ripening to prevent senescence


Sexual ReproductionSexual Reproduction Requires formation of flowers in order to get Requires formation of flowers in order to get

pollination and fertilizationpollination and fertilization Flower InductionFlower Induction

Perfect flowers – both stamen & pistilPerfect flowers – both stamen & pistil

What do the parts of the flower do?What do the parts of the flower do?

Houses gametes, attract pollinatorsHouses gametes, attract pollinators


Pollination & FertilizationPollination & FertilizationPollination – transfer of pollen from anther to Pollination – transfer of pollen from anther to stigmastigma

What is self-pollination?What is self-pollination? Ex. Soybean & tomatoEx. Soybean & tomato

What is cross pollination?What is cross pollination? Ex. Corn & pine treesEx. Corn & pine trees How can this occur?How can this occur?

Fertilization occurs when a small tube from the Fertilization occurs when a small tube from the pollen grain grows through an opening in the ovary pollen grain grows through an opening in the ovary ((micropylemicropyle))


Results in:Results in:Formation of the zygote or seedFormation of the zygote or seedEndospermEndosperm

Fruit Development & MaturationFruit Development & MaturationOvary begins to develop into a fruit after Ovary begins to develop into a fruit after fertilizationfertilizationFruit aids in the dispersal of seedsFruit aids in the dispersal of seeds

What are some adaptations to fruits that aid in dispersal?What are some adaptations to fruits that aid in dispersal?

SeedsSeedsThree main parts of seeds:Three main parts of seeds:

Seed coatSeed coatProtects embryoProtects embryo


Stored food supplyStored food supplyEndosperm or cotyledonsEndosperm or cotyledonsFeed the embryo until it can make its own foodFeed the embryo until it can make its own food

EmbryoEmbryoThe new plantThe new plantPlumulePlumule – young shoot – young shootHypocotylHypocotyl – stem – stemRadicleRadicle – root – root

DormancyDormancySeeds will not germinate during dormancySeeds will not germinate during dormancyAids in protection of the embryo through unfit Aids in protection of the embryo through unfit environmental conditionsenvironmental conditions


Can force seeds out of dormancy if we manipulate Can force seeds out of dormancy if we manipulate the environment, or the seedthe environment, or the seed

Asexual ReproductionAsexual Reproduction Ensures an exact replicate of the parent plantEnsures an exact replicate of the parent plant Enables plants to reproduce even if they don’t Enables plants to reproduce even if they don’t

produce seeds (Banana)produce seeds (Banana) 8 common types of Asexual Reproduction8 common types of Asexual Reproduction

CuttingsCuttingsGraftingGraftingBuddingBudding


LayeringLayering

DivisionDivision

RhizomesRhizomes

StolonsStolons

Tillers/suckersTillers/suckers

Plant ImprovementPlant Improvement Deliberate attempt to change genetic Deliberate attempt to change genetic

architecture of a plantarchitecture of a plant


Modern PracticesModern PracticesWhat is the most common criterion for selection?What is the most common criterion for selection?Tends to affect all other functions of the plantTends to affect all other functions of the plantWhat are some other genetic selections?What are some other genetic selections?Research has allowed farmers to produce more Research has allowed farmers to produce more food from the same amount of landfood from the same amount of land

Basic GeneticsBasic GeneticsOffspring tend to be very similar to the parent, but Offspring tend to be very similar to the parent, but might not be identicalmight not be identical

Ex. Soybeans will be almost identical, Apple trees may Ex. Soybeans will be almost identical, Apple trees may be very differentbe very different


Related to the amount of genetic variationRelated to the amount of genetic variation

New variations can suddenly appear (New variations can suddenly appear (mutationmutation))

Geneticists use these methods to create Geneticists use these methods to create new/improved varietiesnew/improved varieties

Phenotype vs. GenotypePhenotype vs. Genotype

Homozygous vs. HeterozygousHomozygous vs. Heterozygous

Dominant vs. Recessive & Incomplete DominanceDominant vs. Recessive & Incomplete Dominance Self-pollinationSelf-pollination

Produces virtual clones of the parentProduces virtual clones of the parent


Cross-pollinationCross-pollinationGametes originate from different plantsGametes originate from different plantsMore chance for genetic variationMore chance for genetic variationHow does this affect plant breeding and How does this affect plant breeding and propagation of new varieties?propagation of new varieties?

HybridsHybridsObtained by crossing two or more true-breeding Obtained by crossing two or more true-breeding parentsparentsCan produce true-breeding corn lines with Can produce true-breeding corn lines with continual self-pollinationcontinual self-pollination

helps provide uniform parents and seedstockhelps provide uniform parents and seedstock


Hybrids tend to be more vigorous and productiveHybrids tend to be more vigorous and productive Produced from two inbred parent linesProduced from two inbred parent lines

Easy in cornEasy in cornHard in soybeans because they are self-pollinating – Hard in soybeans because they are self-pollinating – must force cross-pollinationmust force cross-pollination

Remove some reproductive parts of the flower to Remove some reproductive parts of the flower to ensure desired crossensure desired cross

Pollen collection and pollination must be done manuallyPollen collection and pollination must be done manually

MutationsMutationsSudden change in genetic expressionSudden change in genetic expressionMost are undesirableMost are undesirableCan produce a desirable changeCan produce a desirable change


Sometimes tough to replicate to due gene Sometimes tough to replicate to due gene interactionsinteractions

Easier in asexually propagated plantsEasier in asexually propagated plants

unit 6: vegetative growth and plant propagation chapters 15 &16

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