Transcript
Plant Structure and Function
Plant Structure and Function
Kareen SturgeonProfessor Emerita, Biology
DepartmentLinfield College
ksturg@linfield.edu
Kareen SturgeonProfessor Emerita, Biology
DepartmentLinfield College
ksturg@linfield.edu
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
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