Support And Transport In Plants Flashcards
What is the main function of roots
Anchorage
Absorption of water and minerals from soil
What is the function of each part of the root (externally)
Mature region - lateral roots develop and branch off
Root hair region (maturation) - has root hairs that increase SA for absorption
Region of cell elongation - new cells elongate in this region
Meristematic region - cells continuously dividing to form new cells
Root cap - surrounds and protects growing point
what is the structure of the epidermis
Single .after of cells
Has root hair extensions
What is the structure of the cortex
Broad band of thin walled parenchyma a cells
Can store starch
Allow for water to move to steel
Have inner layer = endodermis
Walls of endodermal tissue can be thickened with cork to form casperian strips which control move ent of water to the stele
What is the pericycle
Single layer of cells which are able to divide to form the lateral roots
What is the function of xylem
Transports water up the root and gives support to plant
What is the function of phloem
Transports manufactured food (photosynthesis) from plant to root
What are the functions of the stem
Holds leaves, flowers and fruits in best position for photosynthesis, pollination and seed dispersal respectively
Transports water from roots to rest of plant
Transports organic food from leaves to rest of plants
Stores reserve nutrients and water
What is the external structure of stems
Comprised of nodes and internodes
Leaves and side branches grow from nodes
Terminal bud contains meristematic tissue that allows for stem to grow longer
What is the structure and Fu action of the epidermis in stem
Single layer of cells with waxy cuticle layer on top
Protects stem from physical damage and dessication
What is the structure and function of the cortex in the stem
Has three layers:
Collenchyma - have thickened corners and support stem
Parenchyma - thin walled cells for storage
Endodoermis - single layer rectangular cells that store starch
What is the structure and function of vascular bundles
Vascular tissue is in circles of vascular bundles each containing:
Sclerenchyma cap - support
Phloem - transport of food
Xylem - transport of water and support
Cambium - has meristematic tissue that forms new xylem and phloem and result in secondary thickening (growth in widthof stem)
What is the structure and function of vascular bundles
Vascular tissue is in circles of vascular bundles each containing:
Sclerenchyma cap - support
Phloem - transport of food
Xylem - transport of water and support
Cambium - has meristematic tissue that forms new xylem and phloem and result in secondary thickening (growth in widthof stem)
What is the structure of the pith
At centre of stem and consists of parenchyma
What is the structure of the medullary ray
Found between the vascular bundles and consists of parenchyma
Differentiate between primary growth and secondary growth
Primary growth: growth in length that happens in the meristematic regions at the top of root (meristematic region) and stem (terminal bud)
Secondary growth: growth in width that happens in cambium
Differentiate between primary growth and secondary growth
Primary growth: growth in length that happens in the meristematic regions at the top of root (meristematic region) and stem (terminal bud)
Secondary growth: growth in width that happens in cambium
How does bark in plants occur
Outer layer of cortex (collenchyma) becomes meristematic and is called cork cambium. It divides to frm cork cells aka bark
What are the properties and processes of secondary growth
First, cambium is only found within vascular bundles = fascicular cambium
Then it grows and forms a continuous ring that extends across medullary ray = inter-fascicular cambium
Cambium divides forming new xylem and phloem = secondary xylem and phloem
Cambium forms new layer each year ; phloem remains Thin layer just beneath bark
Xylem builds up a new layer each year that is visible as annual rings
Age of tree can be determined by counting annual rings (lighter ring = grew rapidly in spring, darker ring = grew slowly in autumn)
Older xylem in centre can get blocked with lignin and lose its water transport function = heartwood
Xylem on outside still conducting water = sapwood
What three steps can uptake of water and mineral salts be broken down into
Uptake of water and mineral salts by the roots
Movement of water to the xylem of the root
Upward movement of water in the xylem
Which adaptation of the plant makes uptake of water and mineral salts in the soil easy and how
Root hairs:
Increase SA
Surrounded by selectively permeable membrane
Grow between soil particles = close contact with capillary water between soil particles
What does ‘selectively permeable’ mean
A membrane that has tiny pored to allow or water to move through but not for larger molecules such as mineral salts
What is osmosis
Movement of water across a selectively permeable membrane from an area of high water potential to snares of low water potential in an attempt to reach equilibrium
How does water et into the roots of a plant
Cell sap of roots has more dissolved substances than soil water = lower water potential
Gradient allows for watter to move from soil to roots via osmosis
Mineral salts actively pumped tonroots
What is turgor pressure
Pressure exerted on a cell wall membrane by water in the cell
How does water move to the xylem of the root
Water potential in root hairs is higher = water moves down diffusion gradient into cortex
Water can move through the cell walls and intercellular spaces
Water blocked by csperian strip when it reacts endodermis = forces water to move through passage cells to pericycle and then xylem
Which three forces are responsible for upward movement of water from roots to leaves
Capillarity
Root pressure
Transpiration pull
What is capillarity and how does it move water upwards
Capillarity: phenomenon where water spontaneously moves up narrow tubes
Happens because of forces of cohesion and adhesion
What is root pressure and how does it get water up
Root pressure: force that develops in roots
Does not play huge role in upward movement of water
How does transpiration work
Loss of water through stoma creates water potential gradient = water moves to stoma
Force of cohesion forces wholewater column up
Water moving up carries dissolved minerals with it
Transpiration pull = main force moving water upward
Why is transpiration important
Plays important role in movement of water and mineral salts up from the roots
Evaporation of water from the leaves cools the plant
How are leaves adapted to limit transpiration
Size of leaves - smaller leaves = smaller SA for evaporation
Thorns - leaves reduced to thorns to reduce transpiration eg cacti
Leaf organization - leaves may grow vertically to expose less SA to sun or arranged so that lower leaves are directly under top leaves
Position of stomata - position n underside of the tree = less exposure to sunlight
Hairs on leaves - water vapour trapped between hairs = water potential gradient decreased
Thickened cuticle - thicker cuticle = Less transpiration
How do external factors influence
Temperature - high temp raises kinetic energy of water molecules in the intercellular spaces of the leaf = water transpires easily
Light intensity = stomata open in light and close in darkness = changes rate of transpiration
Humidity - lots of moisture in the air = decreases diffusion gradient = transpiration decreases
Wind -wind removes the water vapour just outside the lead making the diffusion gradient steeper and increasing transpiration
Why does wilting happen
When plant loses more water than the roots absorb, the cells lose their turgor pressure and leaves and young stems droop down due to gravity
