Support And Transport In Plants

Question 1

What is the main function of roots

Answer 1

Anchorage
Absorption of water and minerals from soil

Question 2

What is the function of each part of the root (externally)

Answer 2

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

Question 3

what is the structure of the epidermis

Answer 3

Single .after of cells
Has root hair extensions

Question 4

What is the structure of the cortex

Answer 4

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

Question 5

What is the pericycle

Answer 5

Single layer of cells which are able to divide to form the lateral roots

Question 6

What is the function of xylem

Answer 6

Transports water up the root and gives support to plant

Question 7

What is the function of phloem

Answer 7

Transports manufactured food (photosynthesis) from plant to root

Question 8

What are the functions of the stem

Answer 8

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

Question 9

What is the external structure of stems

Answer 9

Comprised of nodes and internodes
Leaves and side branches grow from nodes
Terminal bud contains meristematic tissue that allows for stem to grow longer

Question 10

What is the structure and Fu action of the epidermis in stem

Answer 10

Single layer of cells with waxy cuticle layer on top
Protects stem from physical damage and dessication

Question 11

What is the structure and function of the cortex in the stem

Answer 11

Has three layers:
Collenchyma - have thickened corners and support stem
Parenchyma - thin walled cells for storage
Endodoermis - single layer rectangular cells that store starch

Question 12

What is the structure and function of vascular bundles

Answer 12

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)

Question 13

What is the structure and function of vascular bundles

Answer 13

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)

Question 14

What is the structure of the pith

Answer 14

At centre of stem and consists of parenchyma

Question 15

What is the structure of the medullary ray

Answer 15

Found between the vascular bundles and consists of parenchyma

Question 16

Differentiate between primary growth and secondary growth

Answer 16

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

Question 17

Differentiate between primary growth and secondary growth

Answer 17

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

Question 18

How does bark in plants occur

Answer 18

Outer layer of cortex (collenchyma) becomes meristematic and is called cork cambium. It divides to frm cork cells aka bark

Question 19

What are the properties and processes of secondary growth

Answer 19

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

Question 20

What three steps can uptake of water and mineral salts be broken down into

Answer 20

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

Question 21

Which adaptation of the plant makes uptake of water and mineral salts in the soil easy and how

Answer 21

Root hairs:
Increase SA
Surrounded by selectively permeable membrane
Grow between soil particles = close contact with capillary water between soil particles

Question 22

What does ‘selectively permeable’ mean

Answer 22

A membrane that has tiny pored to allow or water to move through but not for larger molecules such as mineral salts

Question 23

What is osmosis

Answer 23

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

Question 24

How does water et into the roots of a plant

Answer 24

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

Question 25

What is turgor pressure

Answer 25

Pressure exerted on a cell wall membrane by water in the cell

Question 26

How does water move to the xylem of the root

Answer 26

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

Question 27

Which three forces are responsible for upward movement of water from roots to leaves

Answer 27

Capillarity
Root pressure
Transpiration pull

Question 28

What is capillarity and how does it move water upwards

Answer 28

Capillarity: phenomenon where water spontaneously moves up narrow tubes
Happens because of forces of cohesion and adhesion

Question 29

What is root pressure and how does it get water up

Answer 29

Root pressure: force that develops in roots
Does not play huge role in upward movement of water

Question 30

How does transpiration work

Answer 30

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

Question 31

Why is transpiration important

Answer 31

Plays important role in movement of water and mineral salts up from the roots
Evaporation of water from the leaves cools the plant

Question 32

How are leaves adapted to limit transpiration

Answer 32

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

Question 33

How do external factors influence

Answer 33

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

Question 34

Why does wilting happen

Answer 34

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