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Plant Structure and Function

Plant Structure and Function

Kareen SturgeonProfessor Emerita, Biology

DepartmentLinfield College

[email protected]

Kareen SturgeonProfessor Emerita, Biology

DepartmentLinfield College

[email protected]

Photo and figure creditsPhoto and figure credits Campbell & Reece, 2005, Biology, 7th

edition, Pearson/Benjamin Cummings.

Judd et al., 2008, Systematics: A Phylogenetic Approach, 3rd edition, Sinauer Associates, Inc.

Oregon Flora Project Photo Gallery: http://oregonflora.org/gallery.php

Campbell & Reece, 2005, Biology, 7th edition, Pearson/Benjamin Cummings.

Judd et al., 2008, Systematics: A Phylogenetic Approach, 3rd edition, Sinauer Associates, Inc.

Oregon Flora Project Photo Gallery: http://oregonflora.org/gallery.php

Lecture OutlineLecture Outline

Plant morphology: root, stem, leafPlant anatomy: tissues and their

arrangement in the root, stem, & leafPlant function: reproduction,

transport, nutrition, response to stimuli, coevolution

Plant morphology: root, stem, leafPlant anatomy: tissues and their

arrangement in the root, stem, & leafPlant function: reproduction,

transport, nutrition, response to stimuli, coevolution

Structure reflects functionStructure reflects function

Structure includes:Morphology: external structureAnatomy: internal anatomy

Structure includes:Morphology: external structureAnatomy: internal anatomy

Plant morphology

Shoot system: stem, leaves, flowers

Root system: taproot with lateral roots, or fibrous roots (adventitious)

Plant morphology

Shoot system: stem, leaves, flowers

Root system: taproot with lateral roots, or fibrous roots (adventitious)

Plant growthPlant growth

Primary growth: growth in height (herbaceous plants)

Primary growth: growth in height (herbaceous plants)

Secondary growth: growth in girth (woody plants)

Secondary growth: growth in girth (woody plants)

Root primary growthRoot primary growth

Root hair zoneRoot hair zone

The place where absorption occurs!

Disturbance results in transplant shock.

Avoid transplant shock by digging up as much of the root as possible, keeping the root ball moist, and pruning the canopy.

The place where absorption occurs!

Disturbance results in transplant shock.

Avoid transplant shock by digging up as much of the root as possible, keeping the root ball moist, and pruning the canopy.

Nitrogen-fixationNitrogen-fixation Rhizobium bacteria, living in nodules on the roots of legumes, convert atmospheric nitrogen gas (N2) into nitrates (NO3

-) and ammonium ions (NH4

+), forms of nitrogen that plants can use.Why is this process important for life on Earth?

Rhizobium bacteria, living in nodules on the roots of legumes, convert atmospheric nitrogen gas (N2) into nitrates (NO3

-) and ammonium ions (NH4

+), forms of nitrogen that plants can use.Why is this process important for life on Earth?

Mycorrhizal fungi: aid in absorption of water & minerals, especially phosphorus

Mycorrhizal fungi: aid in absorption of water & minerals, especially phosphorus

(arbuscular)

15% of species; eg. pine, oak, willow, birch, walnut; PNW forests!

85% of species; e.g. corn, wheat, legumes; old term, now divided into 3 classes: -arbuscular -ericoid -orchioid

Growth benefits of mycorrhizal associations

Growth benefits of mycorrhizal associations

L: Soybean plant is growing in soil sterilized with a fungicide.

R: Plant is growing in soil inoculated with mycorrhizal fungi.

The first land plants were associated with mycorrhizal fungi.

L: Soybean plant is growing in soil sterilized with a fungicide.

R: Plant is growing in soil inoculated with mycorrhizal fungi.

The first land plants were associated with mycorrhizal fungi.

Shoot primary growthShoot primary growth Identify:

Apical meristem Nodes with leaf and

axillary bud primordia Internodes Dermal, ground, and

vascular tissues How does shoot

anatomy differ from root anatomy?

How do the structural differences in the root and shoot reflect their different functions?

Identify: Apical meristem Nodes with leaf and

axillary bud primordia Internodes Dermal, ground, and

vascular tissues How does shoot

anatomy differ from root anatomy?

How do the structural differences in the root and shoot reflect their different functions?

Stem tissue layersStem tissue layers

Eudicot: vascular bundles in a cylinder

Monocot: vascular bundles scattered

Secondary growth: growth in girth

Secondary growth: growth in girth

Identify: Bark:

Outer: cork (mostly dead tissue)

Inner: 2° phloem (living tissue)

Vascular cambium (a lateral meristem)

2° xylem (wood); growth ring with spring & summer wood

Pith How old is this stem? What tissues are

affected when a tree is girdled?

Identify: Bark:

Outer: cork (mostly dead tissue)

Inner: 2° phloem (living tissue)

Vascular cambium (a lateral meristem)

2° xylem (wood); growth ring with spring & summer wood

Pith How old is this stem? What tissues are

affected when a tree is girdled?

Woody stemWoody stem

Cork

Woody stem

morphology

Woody stem

morphologyOn the stems

provided, identify the features depicted on this slide.

On the stems provided, identify the features depicted on this slide.

Monocot trees: lack of 2° xylem gives them flexibilityMonocot trees: lack of 2°

xylem gives them flexibility

Leaf anatomyLeaf anatomy

During photosynthesis, stomates must remain open. Why?Under what environmental conditions would it be advantageous for plants to keep their stomates closed? Come up with some ideas for how plants might deal with these conflicting demands.

Dilemma: open or close stomates?

Leaf structure and environment

Leaf structure and environment

Deciduous forest

Coniferous forestDesert

Flowering plant reproductionFlowering plant reproductionPistil, composed of 1-many carpels

Pedicel

Calyx

Corolla

Flowering plant life cycleFlowering plant life cycle

Cross-pollination is the rule

Cross-pollination is the rule

Cross-pollination = the transfer of pollen from one plant to the stigma of another plant

Benefits :Increased genetic

diversity among offspring.

Harmful genes are not expressed (recessive alleles are hidden in heterozygotes).

Cross-pollination = the transfer of pollen from one plant to the stigma of another plant

Benefits :Increased genetic

diversity among offspring.

Harmful genes are not expressed (recessive alleles are hidden in heterozygotes).

Barriers to self-fertilization: structural, physiological, geneticBarriers to self-fertilization:

structural, physiological, genetic

Barriers to self-fertilization: Dichogamy: floral parts mature at different timesBarriers to self-fertilization:

Dichogamy: floral parts mature at different times

Barriers to self-fertilization: monoecious and dioecious plants with unisexual

flowers

Barriers to self-fertilization: monoecious and dioecious plants with unisexual

flowers

Monoecious = “one house”: male and female flowers on the same plant

Dioecious = “two houses”: male and female flowers on different plants

Monoecious = “one house”: male and female flowers on the same plant

Dioecious = “two houses”: male and female flowers on different plants

Red alder

Begonia

anthers stigmas

Amorphophallus inflorescence: monoecious and

dichogamous

Amorphophallus inflorescence: monoecious and

dichogamous

Spadix

Fruit development & dispersalFruit development & dispersalFruit = an

enlarged ovary containing seeds

Fruits and/or their seeds are dispersed by wind and animals, especially birds and mammals.

Why do you think it is beneficial for seeds to be dispersed away from their parents?

Fruit = an enlarged ovary containing seeds

Fruits and/or their seeds are dispersed by wind and animals, especially birds and mammals.

Why do you think it is beneficial for seeds to be dispersed away from their parents?

Seed dormancy & germination

Seed dormancy & germination

Dormancy: suspension of growth and development; low metabolic rate.

Germination: resumption of embryo growth.

Requirements: Oxygen Water Temperature Other: heat, cold, abrasion

(mechanical, chemical)

Soil seed pool/bank: natural storage of seeds, often dormant, in soil

Dormancy: suspension of growth and development; low metabolic rate.

Germination: resumption of embryo growth.

Requirements: Oxygen Water Temperature Other: heat, cold, abrasion

(mechanical, chemical)

Soil seed pool/bank: natural storage of seeds, often dormant, in soil

Eudicot

Monocot

Germination requirements: fireGermination requirements: fire

Serotinous cones of lodgepole pine: cones open in heat of fire; seeds require bare, mineral soils to germinate

Serotinous cones of lodgepole pine: cones open in heat of fire; seeds require bare, mineral soils to germinate

Fire-adapted plant communities: fire required for seed germination and/or plant regeneration; e.g. chaparral

Asexual reproductionAsexual reproduction

Root sproutBulb

Stolon (runner) Rhizome

Bulbil

Transport: how does

water get to the tops of

trees?

Transport: how does

water get to the tops of

trees?

Water transport is a passive process

Water transport is a passive process

Xylem is a (mostly) dead tissue.

Water is pulled by evapotranspiration from leaf surfaces.

Pull creates tension. Water molecules can

withstand the tension because they cohere to each other and adhere to the xylem cell walls.

What happens if the tension is broken?

Xylem is a (mostly) dead tissue.

Water is pulled by evapotranspiration from leaf surfaces.

Pull creates tension. Water molecules can

withstand the tension because they cohere to each other and adhere to the xylem cell walls.

What happens if the tension is broken?

Sugar transport is an active process (requiring energy)

Sugar transport is an active process (requiring energy)

Plants expend energy to transport sugar (made by photosynthesis) in phloem, a living tissue.

Movement is bi-directional, depending upon where sugar is needed.

What happens to sugar transport if a tree is girdled?

Plants expend energy to transport sugar (made by photosynthesis) in phloem, a living tissue.

Movement is bi-directional, depending upon where sugar is needed.

What happens to sugar transport if a tree is girdled?

Plant nutritionNutrient = a mineral necessary for plant health

Plant nutritionNutrient = a mineral necessary for plant health

Macronutrients: needed in large quantities: Carbon Oxygen Hydrogen Nitrogen Phosphorus Potassium Sulfur Calcium Magnesium

Macronutrients: needed in large quantities: Carbon Oxygen Hydrogen Nitrogen Phosphorus Potassium Sulfur Calcium Magnesium

Micronutrients: needed in small quantities:ChlorineManganeseIronBoronZincCopperNickelMolybdenum

Micronutrients: needed in small quantities:ChlorineManganeseIronBoronZincCopperNickelMolybdenum

Nutrient deficiency symptoms

Nutrient deficiency symptoms

What to look for:

Where on the leaf: along margins, veins?

In old or young leaves? e.g. N, P, K = phloem mobile nutrients, so deficiencies appear in older leaves.

What color: yellow (chlorosis), blue-red anthocyanins?

Plant responses to their internal & external environments

Plant responses to their internal & external environments

In contrast to animals, plants cope with change in their environment by changing how they grow.

Plants are developmentally plastic as a result of two features:They have indeterminate growth.Their cells are totipotent.

Plant development is mediated by hormones.

In contrast to animals, plants cope with change in their environment by changing how they grow.

Plants are developmentally plastic as a result of two features:They have indeterminate growth.Their cells are totipotent.

Plant development is mediated by hormones.

Plant hormonesPlant hormones Hormone: a substance produced in one

part of the plant body and transported to another part where it elicits a physiological response.

Types:1. Auxin (IAA)2. Cytokinins3. Gibberellins4. Brassinosteroids5. Abscisic acid6. Ethylene

Hormone: a substance produced in one part of the plant body and transported to another part where it elicits a physiological response.

Types:1. Auxin (IAA)2. Cytokinins3. Gibberellins4. Brassinosteroids5. Abscisic acid6. Ethylene

Auxin: phototropismAuxin: phototropism

Auxin: apical dominanceAuxin: apical dominance

Auxin as herbicide: 2,4-DAuxin as herbicide: 2,4-D

Arrowleaf balsamroot, Balsamorhiza sagittata

Leaf abscission: complex hormonal interactions

Leaf abscission: complex hormonal interactions

Abscission = shedding of leaves in preparation for dormancy.

The process is influenced by three hormones: ethylene, auxin, & abscisic acid

Abscission = shedding of leaves in preparation for dormancy.

The process is influenced by three hormones: ethylene, auxin, & abscisic acid

GibberellinsGibberellinsCommercial applications:1. Produces larger fruit

and looser clusters in Thompson Seedless grapes

2. Causes bolting in biennial plants; used for seed production

3. Development of parthenocarpic fruits (e.g. apples, currants, cucumbers, eggplants)

Commercial applications:1. Produces larger fruit

and looser clusters in Thompson Seedless grapes

2. Causes bolting in biennial plants; used for seed production

3. Development of parthenocarpic fruits (e.g. apples, currants, cucumbers, eggplants)

Anticipating seasonal change

Anticipating seasonal change

Clearly, plants can anticipate the seasons and change their pattern of growth and development accordingly.

What do you think is the most important environmental cue that plants use to know when to flower or to go dormant?

Clearly, plants can anticipate the seasons and change their pattern of growth and development accordingly.

What do you think is the most important environmental cue that plants use to know when to flower or to go dormant?

Photoperiod: relative proportion of light to

dark in a 24 hour period

Photoperiod: relative proportion of light to

dark in a 24 hour period

Photoperiodism: growth responses to seasonal changes in

the photoperiod

Photoperiodism: growth responses to seasonal changes in

the photoperiod

Secondary plant metabolites

Secondary plant metabolites

Angiosperms produce an incredible array of chemicals, called secondary metabolites (AKA secondary products).

Three classes:1. Alkaloids; e.g. nicotine, caffeine, morphine,

quinine2. Terpenoids; e.g. essential oils3. Phenolics; e.g. flavonoids, anthocyanins,

coumarins, tannins Why function do these substances serve in

plants?

Angiosperms produce an incredible array of chemicals, called secondary metabolites (AKA secondary products).

Three classes:1. Alkaloids; e.g. nicotine, caffeine, morphine,

quinine2. Terpenoids; e.g. essential oils3. Phenolics; e.g. flavonoids, anthocyanins,

coumarins, tannins Why function do these substances serve in

plants?

Butterflies and plants: biochemical coevolutionButterflies and plants:

biochemical coevolution

Coevolution: the evolution of adaptations in two or more populations that interact closely

Certain compounds characterize whole families of angiosperms; for example,o Plants in the Family Brassicaceae contain toxic mustard oil glycosides.o Thus, most insects ignore this family; but certain groups feed only on this

family; e.g. the butterfly subfamily Pierinae (cabbage whites)o How do you suppose this association came about?

Coevolution: the evolution of adaptations in two or more populations that interact closely

Certain compounds characterize whole families of angiosperms; for example,o Plants in the Family Brassicaceae contain toxic mustard oil glycosides.o Thus, most insects ignore this family; but certain groups feed only on this

family; e.g. the butterfly subfamily Pierinae (cabbage whites)o How do you suppose this association came about?

Coevolution in our own backyard

Coevolution in our own backyard

Fender’s blue butterfly (endangered)

Fender’s blue butterfly (endangered)

Larval host plant, Kincaid’s lupine (threatened)

Larval host plant, Kincaid’s lupine (threatened)

Protecting species = protecting ecosystemsProtecting species =

protecting ecosystems Butterfly is federally

listed as endangered. ESA requires that its

critical habitat be protected. This requires:1. Protecting the larval host

plant & adult nectar sources.

2. Restoring prairies.3. Reintroducing fire.

Thus, protecting species means restoring ecosystem structure and ecological processes.

Butterfly is federally listed as endangered.

ESA requires that its critical habitat be protected. This requires:1. Protecting the larval host

plant & adult nectar sources.

2. Restoring prairies.3. Reintroducing fire.

Thus, protecting species means restoring ecosystem structure and ecological processes.

Calochortus tolmiei

Dichelostemma congestum