Vascular Plant Structure, Growth, and Development
Cell: fundamental unit of life
Tissue: group of cells consisting of 1+ cell types that perform a specialized function
Organ: consists of several type of tissues that carry out particular functions
Vascular Plants: plants that can transport things up and down
Root system: underground
Roots rely on sugar produced by photosynthesis in the shoot system (cannot make sugar by themselves)
Root: organ with important functions
anchoring the plant
absorbing minerals and water
storing carbs (excess made in photosynthesis
because plants aren’t always guaranteed to have sunlight
Lateral roots: roots that emerge from the sides
Help anchor
Spread, help absorb nutrients
Primary root: first root to emerge from the seed
Taproot System: one main root and branches
Taproot: develops from primary root & anchors plant in soil
Fibrous root system: lots of small roots (no need for strong anchor)
Adventitious roots: side roots that arise from the stem & give rise to branching lateral roots
Root hairs: extensions of epidermal cells forming near root tip
Increase surface area, more absorption
Mycorrhizal associations: roots have fungus living in it that help them transform something they cannot use into something they can
ex/ Break down unusable nitrogen (symbiotic relationship)
Types of Roots
Prop roots: more anchorage
Storage roots: store carbs
Pneumatophores: some can do gas exchange (similar to leaves)
“Strangling” aerial roots: add further anchorage
Buttress roots: very tall and thin roots above ground, typically in forests and jungles (spread far and wide)
Shoot system: above ground
Shoots rely on water and minerals absorbed by the root system
Stem: plant organ consisting of nodes & internodes
Nodes: points at which leaves are attached
Internodes: space between nodes
Apical bud: causes elongation of a young shoot
where plant grows taller
Axillary bud: structure that can form a lateral branch, thorn, or flower
not main bud for height, additional buds for leaves, flowers, etc.
Leaf: main photosynthetic organ
Intercept light, exchange gases, dissipate heat, and defend the plant from herbivores and pathogens
ex/ chemical coat prevents fungus from attacking plant
Consist of blade and petiole
Blade: flat part
Petiole: stalk that joins leaf to node of stem
Chloroplasts in leaf
light shines & photosynthesis occurs
Why are leaves flat?
To maximize surface area and sun exposure
Monocot: 1 thing comes out of seed
Parallel veins
Vascular bundles are scattered throughout the ground tissue
Eudicot: 2+ things come out of seed
Branching veins
Vascular tissue consists of vascular bundles arranged in a ring
Vein: the vascular tissue of leaves
How do we categorize plants?
Determine if monocot or eudicot
What do the flowers look like?
What do the leaves look like?
Simple leaf: 1 leaf
Compound leaf: has several individual leaflets
Evolutionary Adaptations of Leaves
Tendrils: help anchor it above the ground
Spines: defend
Storage leaves: store carbs
Reproductive leaves: leaves can reproduce
Tissue system: interconnected leaf, stem, and root
Dermal tissue system
Nonwoody plants
Dermal tissue system: protection of the plant, consists of epidermis
Cuticle: waxy coating that helps prevent water loss from the epidermis (too hot from the sun)
No periderm
Woody plants
Periderm: outer layer protective tissues that replace epidermis in older regions of stems and roots
They have both periderm & epidermis
Guard cells: epidermal cells that facilitate gas exchange in shoots
too hot→ close
prevent water loss
cold→ open
Trichomes: outgrowths of the shoot epidermis that can reduce water loss and reflect light, also defend against insects
Vascular tissue system: facilitates transport of materials through the plant & provides mechanical support
Xylem: conducts water & dissolved minerals upwards from roots to shoots
Phloem: transports sugars from leaves (where they are made) to storage/sites of growth (down)
Stele: everything except the leaves
In angiosperms, stele of root is central solid vascular cylinder (in the middle)
Angiosperms: plants that make flowers
Ground tissue system: tissues that are neither dermal nor vascular
Cells specialized for storage, photosynthesis, support, and transport (everything else)
Pith: ground tissue inside vascular tissue
Cortex: ground tissue outside vascular tissue
Stem cells are not differentiated
Structure changes depending on function
Indeterminate growth: plant grows until death
Determinate growth: stop growing after certain age/size
Meristems: unspecialized tissues made of dividing cells
how plants grow continuously
Apical Meristems: located at tips of roots and shoots (up and down)
Primary growth: growing vertically
Lateral Meristems: grow sides/in diameter/in width (secondary growth)
Vascular Cambium: adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
Cork Cambium: replaces epidermis with periderm (thicker and tougher)
Initials: stem cells (new cells) that remain in meristem and produce more cells
unspecialized
the farther from meristem, they get specialized
Primary Meristems
Protoderm: produces dermal tissue
Ground meristem: produces ground tissue
Procambium: produces vascular tissue
Classification of Angiosperms
Annuals: complete life cycle in <=1 yr
Biennials: require 2 growing seasons
Perennials: live for many years
“Life cycle”- moment of sprouting→ reproduction
Root Cap: collection of cells that protects root apical meristem as root pushes through soil
Primary Growth of Shoots
Shoot apical meristem: dome-shaped mass of dividing cells at shoot tip
leaves of apical bud protect meristem
Axillary buds develop from meristematic cells left at the bases of lead primordia (collection of cells that were told to become leaves)
Kept dormant by chemical communication from apical bud (apical dominance)
If axillary bud + apical bud closer→ more inhibited
Released if shoot tip removed or shaded
Leaf Growth and Anatomy
Leaves develop from lead primordia along sides of shoot apical meristem
Epidermis (outer dermal tissue) in leaves interrupted by stomata (pores that allow CO2 and O2 exchange between air and photosynthetic cells)
Major evaporative loss of water, so located on bottom of leaf
Each stomatal pore has 2 guard cells to regulate opening and closing
Mesophyll: where photosynthesis occurs; ground tissue of leaf
Between upper and lower epidermis
2 layers:
Palisade mesophyll: upper part of leaf
Spongy mesophyll: lower part of leaf (loose for gas exchange)
Veins are leaf’s vascular bundles; skeleton of leaf
Each vein enclosed by protective bundle sheath (xylem & phloem)
Why?
If xylem and phloem damaged, no transport can occur
Secondary Growth
Growth in thickness produced by lateral meristems
Occurs in gymnosperms (don’t make flowers) & many eudicots; RARE in monocots
Occurs in stems and roots of woody plants; RARELY in leaves
Consists of growth of tissues produced by vascular cambium and cork cambium
Growth, Morphogenesis, and Cell Differentiation Produce the Plant Body
Developmental plasticity: effect of environment on development
Plant can change form depending on environmental triggers
Morphogenesis: form body shapes
Growth is irreversible
Cell differentiation
Certain genes become accessible/inaccessible for the lifetime of the cell
Model
Arabidopsis
Why is it a model?
Small size, short generation time, abundant seed production, small genome size
Appearance changes depending on environment (genes on/off)
Easily transformed with transgenes (genes from different organism)
Increases # of cells & potential for growth
Cell elongation: process responsible for increase in plant size
Prophase: nucleus dissolves
Metaphase: chromosomes line up in middle
Anaphase: chromosomes separated by microtubules
Microtubules: pull apart chromosomes; become concentrated into ring called preprophase band that predicts future plane of cell division
Telophase: cell dividing
Cytokinesis: pinching off middle part
Transverse cell division: left and right
Longitudinal cell division: up and down
Symmetry of cell division & distribution of cytoplasm affects cell fate
Concentration of chemicals→ different genes turn on
Axis of division is predetermined
Polarity: condition of having structural/chemical differences at opposite ends of organism
Asymmetrical cell divisions
Uneven distribution of molecules→ determine what is the root and what is the shoot
Plant cells grow fast by intake and storage of water in large central vacuole
Cellulose microfibrils in cell wall restrict direction of cell elongation (prevent from lysing)
Morphogenesis & Pattern Formation
Pattern formation: development of specific structures in specific locations
Lineage-based mechanisms: cell fate determined early in development and passed on to daughter cells (animals)
Position-based mechanisms: cell fate determined by final position (plants)
Homeotic (Hox) Genes: affect # and placement of appendages in embryos
MADS-box genes: position & # of plant organs
KNOTTED-1: development of lead morphology (3d shape)
Different cells have different proteins
Different structure→ different function
Gene activation/inactivation depends on cell-to-cell communication (hormones and signals)
Phase changes: developmental stages
Juvenile phase→ adult vegetative stage→ adult reproductive stage
Occur within shoot apical meristem
Flower Formation: phase change from vegetative growth→ reproductive growth
Triggered by environmental cues & internal signals
ex/ sudden increase in water
Associated with switching on of floral meristem identity genes
takes energy to flower
Order of primordium’s emergence determines its fate:
Sepal: supports flower after blooming
Petal: attract pollinators
Stamen: male reproductive part; make pollen
Carpel: female reproductive part
3 classes of floral organ identity genes
ABC Hypothesis: how floral organ identity genes direct the formation of the four types of floral organs
A→ sepal
A+B→ petal
B+C→ stamen
C→ carpel
Cell: fundamental unit of life
Tissue: group of cells consisting of 1+ cell types that perform a specialized function
Organ: consists of several type of tissues that carry out particular functions
Vascular Plants: plants that can transport things up and down
Root system: underground
Roots rely on sugar produced by photosynthesis in the shoot system (cannot make sugar by themselves)
Root: organ with important functions
anchoring the plant
absorbing minerals and water
storing carbs (excess made in photosynthesis
because plants aren’t always guaranteed to have sunlight
Lateral roots: roots that emerge from the sides
Help anchor
Spread, help absorb nutrients
Primary root: first root to emerge from the seed
Taproot System: one main root and branches
Taproot: develops from primary root & anchors plant in soil
Fibrous root system: lots of small roots (no need for strong anchor)
Adventitious roots: side roots that arise from the stem & give rise to branching lateral roots
Root hairs: extensions of epidermal cells forming near root tip
Increase surface area, more absorption
Mycorrhizal associations: roots have fungus living in it that help them transform something they cannot use into something they can
ex/ Break down unusable nitrogen (symbiotic relationship)
Types of Roots
Prop roots: more anchorage
Storage roots: store carbs
Pneumatophores: some can do gas exchange (similar to leaves)
“Strangling” aerial roots: add further anchorage
Buttress roots: very tall and thin roots above ground, typically in forests and jungles (spread far and wide)
Shoot system: above ground
Shoots rely on water and minerals absorbed by the root system
Stem: plant organ consisting of nodes & internodes
Nodes: points at which leaves are attached
Internodes: space between nodes
Apical bud: causes elongation of a young shoot
where plant grows taller
Axillary bud: structure that can form a lateral branch, thorn, or flower
not main bud for height, additional buds for leaves, flowers, etc.
Leaf: main photosynthetic organ
Intercept light, exchange gases, dissipate heat, and defend the plant from herbivores and pathogens
ex/ chemical coat prevents fungus from attacking plant
Consist of blade and petiole
Blade: flat part
Petiole: stalk that joins leaf to node of stem
Chloroplasts in leaf
light shines & photosynthesis occurs
Why are leaves flat?
To maximize surface area and sun exposure
Monocot: 1 thing comes out of seed
Parallel veins
Vascular bundles are scattered throughout the ground tissue
Eudicot: 2+ things come out of seed
Branching veins
Vascular tissue consists of vascular bundles arranged in a ring
Vein: the vascular tissue of leaves
How do we categorize plants?
Determine if monocot or eudicot
What do the flowers look like?
What do the leaves look like?
Simple leaf: 1 leaf
Compound leaf: has several individual leaflets
Evolutionary Adaptations of Leaves
Tendrils: help anchor it above the ground
Spines: defend
Storage leaves: store carbs
Reproductive leaves: leaves can reproduce
Tissue system: interconnected leaf, stem, and root
Dermal tissue system
Nonwoody plants
Dermal tissue system: protection of the plant, consists of epidermis
Cuticle: waxy coating that helps prevent water loss from the epidermis (too hot from the sun)
No periderm
Woody plants
Periderm: outer layer protective tissues that replace epidermis in older regions of stems and roots
They have both periderm & epidermis
Guard cells: epidermal cells that facilitate gas exchange in shoots
too hot→ close
prevent water loss
cold→ open
Trichomes: outgrowths of the shoot epidermis that can reduce water loss and reflect light, also defend against insects
Vascular tissue system: facilitates transport of materials through the plant & provides mechanical support
Xylem: conducts water & dissolved minerals upwards from roots to shoots
Phloem: transports sugars from leaves (where they are made) to storage/sites of growth (down)
Stele: everything except the leaves
In angiosperms, stele of root is central solid vascular cylinder (in the middle)
Angiosperms: plants that make flowers
Ground tissue system: tissues that are neither dermal nor vascular
Cells specialized for storage, photosynthesis, support, and transport (everything else)
Pith: ground tissue inside vascular tissue
Cortex: ground tissue outside vascular tissue
Stem cells are not differentiated
Structure changes depending on function
Indeterminate growth: plant grows until death
Determinate growth: stop growing after certain age/size
Meristems: unspecialized tissues made of dividing cells
how plants grow continuously
Apical Meristems: located at tips of roots and shoots (up and down)
Primary growth: growing vertically
Lateral Meristems: grow sides/in diameter/in width (secondary growth)
Vascular Cambium: adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
Cork Cambium: replaces epidermis with periderm (thicker and tougher)
Initials: stem cells (new cells) that remain in meristem and produce more cells
unspecialized
the farther from meristem, they get specialized
Primary Meristems
Protoderm: produces dermal tissue
Ground meristem: produces ground tissue
Procambium: produces vascular tissue
Classification of Angiosperms
Annuals: complete life cycle in <=1 yr
Biennials: require 2 growing seasons
Perennials: live for many years
“Life cycle”- moment of sprouting→ reproduction
Root Cap: collection of cells that protects root apical meristem as root pushes through soil
Primary Growth of Shoots
Shoot apical meristem: dome-shaped mass of dividing cells at shoot tip
leaves of apical bud protect meristem
Axillary buds develop from meristematic cells left at the bases of lead primordia (collection of cells that were told to become leaves)
Kept dormant by chemical communication from apical bud (apical dominance)
If axillary bud + apical bud closer→ more inhibited
Released if shoot tip removed or shaded
Leaf Growth and Anatomy
Leaves develop from lead primordia along sides of shoot apical meristem
Epidermis (outer dermal tissue) in leaves interrupted by stomata (pores that allow CO2 and O2 exchange between air and photosynthetic cells)
Major evaporative loss of water, so located on bottom of leaf
Each stomatal pore has 2 guard cells to regulate opening and closing
Mesophyll: where photosynthesis occurs; ground tissue of leaf
Between upper and lower epidermis
2 layers:
Palisade mesophyll: upper part of leaf
Spongy mesophyll: lower part of leaf (loose for gas exchange)
Veins are leaf’s vascular bundles; skeleton of leaf
Each vein enclosed by protective bundle sheath (xylem & phloem)
Why?
If xylem and phloem damaged, no transport can occur
Secondary Growth
Growth in thickness produced by lateral meristems
Occurs in gymnosperms (don’t make flowers) & many eudicots; RARE in monocots
Occurs in stems and roots of woody plants; RARELY in leaves
Consists of growth of tissues produced by vascular cambium and cork cambium
Growth, Morphogenesis, and Cell Differentiation Produce the Plant Body
Developmental plasticity: effect of environment on development
Plant can change form depending on environmental triggers
Morphogenesis: form body shapes
Growth is irreversible
Cell differentiation
Certain genes become accessible/inaccessible for the lifetime of the cell
Model
Arabidopsis
Why is it a model?
Small size, short generation time, abundant seed production, small genome size
Appearance changes depending on environment (genes on/off)
Easily transformed with transgenes (genes from different organism)
Increases # of cells & potential for growth
Cell elongation: process responsible for increase in plant size
Prophase: nucleus dissolves
Metaphase: chromosomes line up in middle
Anaphase: chromosomes separated by microtubules
Microtubules: pull apart chromosomes; become concentrated into ring called preprophase band that predicts future plane of cell division
Telophase: cell dividing
Cytokinesis: pinching off middle part
Transverse cell division: left and right
Longitudinal cell division: up and down
Symmetry of cell division & distribution of cytoplasm affects cell fate
Concentration of chemicals→ different genes turn on
Axis of division is predetermined
Polarity: condition of having structural/chemical differences at opposite ends of organism
Asymmetrical cell divisions
Uneven distribution of molecules→ determine what is the root and what is the shoot
Plant cells grow fast by intake and storage of water in large central vacuole
Cellulose microfibrils in cell wall restrict direction of cell elongation (prevent from lysing)
Morphogenesis & Pattern Formation
Pattern formation: development of specific structures in specific locations
Lineage-based mechanisms: cell fate determined early in development and passed on to daughter cells (animals)
Position-based mechanisms: cell fate determined by final position (plants)
Homeotic (Hox) Genes: affect # and placement of appendages in embryos
MADS-box genes: position & # of plant organs
KNOTTED-1: development of lead morphology (3d shape)
Different cells have different proteins
Different structure→ different function
Gene activation/inactivation depends on cell-to-cell communication (hormones and signals)
Phase changes: developmental stages
Juvenile phase→ adult vegetative stage→ adult reproductive stage
Occur within shoot apical meristem
Flower Formation: phase change from vegetative growth→ reproductive growth
Triggered by environmental cues & internal signals
ex/ sudden increase in water
Associated with switching on of floral meristem identity genes
takes energy to flower
Order of primordium’s emergence determines its fate:
Sepal: supports flower after blooming
Petal: attract pollinators
Stamen: male reproductive part; make pollen
Carpel: female reproductive part
3 classes of floral organ identity genes
ABC Hypothesis: how floral organ identity genes direct the formation of the four types of floral organs
A→ sepal
A+B→ petal
B+C→ stamen
C→ carpel