Chapter 35 Flashcards
Primary growth
Extension of shoots and roots
Why do plants exhibit indeterminate growth?
they have meristems
Meristems
populations of undifferentiated cells that are able to continuously divide and produce new cells
populations of undifferentiated cells that are able to continuously divide and produce new cells
Meristems
Extension of shoots and roots
Primary growth
Apical meristems
located at the tip of each root and shoot (RAM and SAM)
What happens as cells in the apical meristem divide, enlarge, and differentiate
root and shoot tips extend
During primary growth, cells produced by the meristem give rise to three…
primary meristems
Primary meristems
Produce the mature tissues of the plant
Three types of primary meristems
- Protoderm
- Ground Meristem
- Procambium
Tissue system that forms from protoderm
Dermal tissue
Tissue system that forms from ground meristem
ground tissue
Tissue system that forms from procambium
Vascular tissue
What is RAM protected by?
root cap
What does the root cap do?
sense gravity and determine direction of growth
What does the root cap secrete
mucigel
Mucigel
helps lubricate root tip as it moves through the soil
Zone of cellular division
production of new root cells
Zone of cellular elongation
composed of cells that are dividing to increase in length
What is the zone of cellular elongation responsible for?
movement of roots in soil (push RAM through soil)
Zone of differentiation (maturation)
where older cells complete differentiation into distinct cell types
Where are the youngest cells during root growth?
Near the root tip
What does 1st degree root growth produce?
epidermis, ground tissue, and vascular tissue
Ground tissue (root system)`
mostly parenchyma cells - cortex
Cortex
region between vascular cylinder and epidermis
Function of the cortex
extracellular diffusion of water, minerals, and O2 from root hairs
Endodermis (root system)
innermost region of cortex
What does the endodermis surround
vascular cylinder
What does the endodermis function in?
regulating passage of substances from soil into vascular system
Eudicot root structure
- Dermal Tissue System
- Ground Tissue System
- Vascular Tissue System
Dermal Tissue System (Eudicot root structue)
Epidermis
Ground Tissue System (Eudicot root structue)
- cortex (contains starch grains - purple)
2. endodermis (surrounds vascular cylinder/column)
Vascular Tissue System (Eudicot root structue)
- Pericycle
- Xylem Tissue
- Phloem Tissue
Pericycle (vascular tissue system)
production of lateral roots
Xylem tissue (vascular tissue system)
conducts water
Phloem tissue (vascular tissue system)
conducts photosynthates (between the ‘arms’)
Dermal Tissue System (monocot root structure)
Epidermis
Ground Tissue System (monocot root structure)
Cortex, endodermis, and pith
Vascular tissue system (monocot root structure)
- vascular cylinder
- pericycle
xylem and phloem for rings around core of parenchyma cells (pith)
pericycle
outermost cell layer of vascular cylinder just inside endodermis
SAM
dome-shaped mass of dividing cells at shoot tip
Leaf primordia
site of leaf development
When does leaf primordia take place?
during SAM
What happens during leaf primordia
within buds, young leaves are close together. Shoot elongation results from lengthening of internodes
Apical dominance
Axillary buds remain dormant due to inhibition by apical bud
What does branching result from?
releasing apical dominance (pruning/herbivory)
What does 1st degree growth in shoots give rise to?
dermal, ground, and vascular tissues
In stems, vascular tissues are…
grouped into vascular bundles that run length of stem
Dermal Tissue System in primary shoot system in eudicots
epidermis
Ground tissue system in primary shoot system in eudicots
- pith
- cortex
- mostly parenchyma cells
- collenchyma cells below epidermis
- sclerenchyma cells
Pith in ground tissue system of eudicot shoot
in center
cortex in ground tissue system of eudicot shoot
external to vascular tissue
Collenchyma cells below epidermis
provide strength during growth
Sclerenchyma cells in eudicot shoot system
provide strength to stems no longer elongating
Vascular tissue system in eudicot shoot system
vascular bundles arranged in a ring
- xylem
- phloem
- vascular cambium
Dermal tissue system in monocot stem
epidermis
Ground tissue system in monocot stem
- no formal cortex
- similar to dicots (regarding tissue/cell types)
Vascular tissue system in monocot stem structure
vascular bundles scattered throughout stem
Dermal tissue system in leaves
- epidermis (covered by cuticle)
- guard cells (surround opening called stomata - for gas exchange)
Ground tissue system in eudicot leaf structure
- Mesophyll (middle leaf)
- Palisade mesophyll
- Spongy mesophyll
Mesophyll (ground tissue system in eudicot leaf structure)
made up of parenchyma cells that function in photosynthesis
Palisade mesophyll (ground tissue system in eudicot leaf structure)
elongated parenchyma cells on upper part of leaf
Spongy mesophyll
loosely arranged parenchyma cells with air spaces for gas exchange
Ground tissue in monocot leaf structure
only spongy mesophyll
Vascular tissue system of leaves
continuous with that of stem
- xylem
- phloem
- veins enclosed by bundle of sheath
Xylem of leaves
brings H2O in for psyn
Phloem of leaves
transports photosynthates to other parts of plant
Veins enclosed by bundle sheath does what?
regulates movement of substances between vascular tissue and mesophyll
Vascular system of eudicots
have net venation
Vascular system of monocots
have parallel venation
What does secondary growth increase?
the width of the plant body via lateral meristems
What do lateral meristems/secondary growth function in?
increasing the amount of conducting tissue available and provides structural support for extensive primary growth
What does secondary growth produce
wood
Where does secondary growth occur
in species that have a cambium in addition to apical meristems
Cambium (secondary meristem/lateral meristem)
- made of thin layers of meristematic cells that form cylinders that run the length of a root or stem
- can divide to increase width of roots and shoots
- two types (vascular and cork)
Apical meristem (first degree growth)
- form dome-shaped cell clusters localized in root and shoot tips
- cells divide to extend root and shoot tips
- two locations: root tips (RAM) and shoot tips (SAM)
Vascular cambium
- produces secondary phloem to the outside
2. produces secondary xylem to the inside
Initials oriented perpendicular to the stem/root produce…
vascular rays
Vascular rays
connect secondary xylem and phloem
Do we observe second degree growth in monocots?
No
Indeterminate growth
Plants never stop growing
Plant hierarchial organization
system
organs
tissues systems/tissues
cells
Shoot system
stems and leaves (organs)
Root system
Roots (organ)
Characteristics of root system
- underground
- anchor plant to soil
- absorb water and minerals from soil
- conducts water and minerals to shoot
- stores carbohydrates and other reserves
Characteristics of shoot system
- above ground biomass
- harvests light and carbon dioxide to produce sugars
- elevate reproductive organs
- exports photosynthates (sugar and other carbohydrates) to root system
Characteristics of leaves
- vast majority of photosythesis occurs here
- exchange gases with atmosphere
- dissipate heat
- defend against herbivores and pathogens
How do roots rely on the shoot system?
they rely on sugar produced via photosynthesis in shoot system
How do shoots rely on the shoot system?
they rely on water and minerals absorbed by the root system
Primary root (first root)
emerges from seed embryo
Lateral branches
extend from primary root (increase ability to anchor/aquire nutrients)
Root hairs on elongating roots
increase root surface area and are primary site of nutrient absorption
Where are root hairs found?
on the tip of the root
Where does most absorption take place?
Tip of the root
Taproot system
- primary root becomes taproot
- prevents toppling over
- absorption is primarily funcion of lateral roots
Where are taproots often seen?
In dicots
Fibrous root system
primary root dies early and does not form a taproot
Adventitious roots
Many small roots emerge from stem (part of fibrous root system)
Where is the fibrous root system often seen?
in monocots
What are root systems of different plants…
are adapted to environment and minimize competition
What can roots change in response to?
environmental conditions
Major organs of the shoot system
stems and leaves
What does the stem consist of?
nodes and internodes
Apical buds
elongate stems
Axillary buds
develop branching
What do shoot systems do?
adapt to the environment and minimize competition
What happens if you remove a terminal/apical bud?
apical dominance (lateral branches begin to grow)
Blade
wide, expanded, flat portion of the leaf
Petiole
the stalk of the leaf that joins leaf to stem
All organs are made up of _____ that form ______.
tissues; tissues system
Tissue type to dermal tissue system
epidermis
Tissue types of vascular tissue system
xylem and phloem
Tissue types to ground tissue system
parnchyme, collenchyma, and sclerenchyma
Functions of the dermal tissue system
to protect the plant from water loss, disease, and herbivores
What is the dermal tissue system made up of?
Epidermal tissue
What cell types does the epidermal tissue contain?
Epidermal cells, guard cells (surround stomata), trichomes
Epidermal cells
secrete the cuticle that covers the shoot system, protectsleaves, and reduces water loss
Stomata
allow carbon dioxide to ender photosynthetically active tissues
What does the stomata consist of?
two guard cells which change shape to open or close the pore
Trichomes
protective hairlike structures made up of specialized epidermal cells
Funcions of the vascular tissue system
support and long distance transport of water and nutrients
What is the vascular tissue system collectively called?
the stele (or vascular cylinder/column)
Xylem tissue
contain tracheids and vessel elements
Phloem tissue
contain sieve-tube elements and companion cells
What does xylem tissue do?
conduct water and nutrients from root to shoot (also side to side)
All xylem cells are…
dead at maturity and filled with fluid instead of cytoplasm
Xylem cells - tracheids
- long and slender
- tapered ends
- water moves through pits
- spindle shaped
Xylem cells - vessel elements
- short and wide
- aligned end to end (joined at perforation plate)
- water flows through perforation plates (and pits)
What does phloem tissue do?
conduct sugars (photosynthates) throughout plant body (not uniderectional like xylem)
Phloem cells are…
alive at maturity
Phloem cells - sieve tube elements (members)
- long, thin cells
- no nuclei and most other organelles (easier to transport nutrients…)
- sugars and nutrients transported from cell to cell through sieve plates
Phloem cells - companion cells
- don’t conduct material
- assist with loading and unloading carbohydrates and nutrients from solution inside sieve tube members
- their organelles serve the sieve-tube members as well
Functions of the ground tissue system
photosynthesis, carbohydrate storage, support, and short-distance transport
Parenchyma cells
- thin primary cell walls
- primary site of photosythesis (leaves)
- store starch (roots)
- mature cells are alive and still able to divide (wound repair)
Collenchyma cells
- thickness of primar cell wall varies (some area of secondary wall thickening)
- can elongate even when mature (are alive)
- Funcion in “flexible” support (grouped in strands)
- Found in elongating stems andn petioles of leaves
Sclerenchyma cells
- thin primary wall
- can’t elongate
- funcion in support (many dead at maturity)
- produce thick secondary cell wall containing lignin
Two types of sclerenchyma cells
fibers, sclereids
Fibers
extremely elongated for support
Sclereids
relatively short for protection
