7- transport in plants

Question 1

Parenchyma

Answer 1

• cells serve to support plant when turgid
• prevent plant from wilting
• packing+storage
• cells carry out photosynthesis

Question 2

collenchyma

Answer 2

living cells with unevenly thickened cellulose cell walls- responsible for providing support

Question 3

schlerenchyma

Answer 3

dead cells with lignified walls- support

Question 4

What is the main function of companion cells in phloem tissue?

Answer 4

release energy for sieve tube elements

Question 5

xylem vessel features

Answer 5

• elongated cells with end walls broken down,
• located in vascular bundles in stem+centrally in roots

Question 6

vascular tissue in leaf

Answer 6

transport water and nutrients

Question 7

companion cell features

Answer 7

release energy for sieve tube elements

Question 8

what is the relationship between humidity and the water vapour gradient between the leaf and atmosphere

Answer 8

high humidity decreases the water vapour gradient

Question 9

describe the adhesion of water molecules in the xylem

Answer 9

hydrogen bonding between polar water molecules and non-polar cellulose in xylem vessel walls

Question 10

what do stomata do in the water movement process in plants

Answer 10

allow water to evaporate from leaves

Question 11

According to the mass flow hypothesis, what happens at the source to initiate translocation?

Answer 11

solutes like sucrose are actively loaded into sieve tube elements

Question 12

Which of the following is a source of assimilates for translocation?

Answer 12

leaves

Question 13

How are hydrogen ions (H+) involved in the active loading of sucrose into the phloem?

Answer 13

co-transported with sucrose into companion cell

Question 14

Describe the difference in leaves of monocotyledon and dicotyledon?

Answer 14

leaves in monocotyledon are long, narrow - have no petiole and have parallel veins (grass)
The leaves in dicotyledon are leaves with blades, they are wide, petiole is present and have branched veins

Question 15

Describe the difference in the stem of monocotyledon and dicotyledon?

Answer 15

Monocotyledon have scattered vascular bundles or as dicotyledon have vascular bundles which are arranged in a ring

Question 16

where are xylem + phloem distributed in the stems, roots, leaves of plants

Answer 16

stems: vascular bundles arranged forming ring around outer part of stem
roots: vascular bundles found in centre
leaves: form networks of veins in leaf

Question 17

how does companion cell structure relate to function

Answer 17

large number of mitochondria+ribosomes, provide energy and proteins for active transport of substances

Question 18

what are diff tissues in a typical plant leaf and their functions

Answer 18

upper epidermis with waxy cuticle: reduces water VAPOUR loss
palisade mesophyll: photosynthesis
spongy mesophyll: has air spaces for gas diffusion
lower epidermis: has stomata surrounded by guard cells for gas exchange
vascular tissue: transports water and nutrients

Question 19

State two environmental factors that affect the rate of transpiration.
For each factor given, explain how it affects the rate of transpiration

Answer 19

Temperature: increased temperature increases the rate of evaporation/diffusion OR at high temperatures, stomata close so transpiration stops
Humidity: increased humidity decreases rate of transpiration as the water potential gradient is less steep
wind speed OR air movement: Higher wind speed causes a steeper water potential gradient OR at high wind speed, stomata close and transpiration stops
water availability: reduced water availability causes stomata to close and transpiration stops OR when more water is available, there is a steeper water potential gradient between roots and leaves, so transpiration is faster
light intensity: higher light intensity increases transpiration rate as more stomata open OR at very high light intensity, stomata close so transpiration stops

Question 20

function of vascular tissues

Answer 20

form transport systems in plants. Xylem transports water and minerals whereas phloem is used for TRANSLOCATION of sucrose and amino acids from the source to the sink

Question 21

location of xylem

Answer 21

• in stem facing the center and arranged in vascular bundles
• in roots, it has a series of arms between which the phloem is found

Question 22

location of phloem

Answer 22

in stem together with xylem forming vascular bundles that are surrounded by sclerenchyma, as phloem faces outwards.
in roots, found between a series of arms made of xylem vessels

Question 23

What is the xylem vessel element?

Answer 23

dead, lignified cell found in xylem so specialized for transporting water and for support The ends of the cells break down and join with neighboring elements to form long tubes called xylem vessels

Question 24

xylem vessel

Answer 24

dead empty tube with lignified walls through which water is transported in plants it is formed by xylem vessel elements lined up end to end

Question 25

Describe the apoplast pathway

Answer 25

water enters cell wall+moves through intercellular spaces only

Question 26

Describe the symplast pathway

Answer 26

water enters cytoplasm by osmosis through CSM(partially permeable) moves in vacuole sap through tonoplast+cell-cell through plasmodesmata, adjacent CSM+CW cells

Question 27

what are magnesium ions used for in plant

Answer 27

gives chlorophyll green colour translation

Question 28

Lignified cell walls -> function

Answer 28

Adds strength to **withstand hydrostatic pressure** so vessels do not collapse. Impermeable to water

Question 29

no end plates -> function in xylem

Answer 29

Allows for **mass flow** of water and dissolved solutes as cohesive (between water molecules) and adhesive (between water molecules and xylem wall)**forces are not impeded**

Question 30

no protoplasm- cells are dead when mature

Answer 30

Does not impede the mass flow of water and dissolved solutes

Question 31

pits in walls-> xylem function

Answer 31

**Lateral movement** of water allows for continuous flow in case of air bubbles forming in the vessel

Question 32

phloem made of

Answer 32

made up of **sieve tube elements** which are the main conducting cells and **companion** cells - **parenchyma** for storage and strengthening fibres

Question 33

function of phloem tissue in a plantis

Answer 33

Transport organic compounds (assimilates), particularly sucrose,from the source (e.g. leaf)to the sink (e.g. roots). **organic compounds** are **dissolved in water** to form sap

Question 34

sieve tube elements

Answer 34

elements line up end to end to form a continuous tube They transport sugars and nutrients up and down the plants in sieve cells

Question 35

adaptations of sieve tubes for transport pores cellulose CW no nucleus, ribosomes, vacuole in mature cells thin cytoplasm

Answer 35

- allows continuous movement of organic substances - strengthens wall to withstand hydrostatic pressures moving assimilates - maximises space for assimilate movement - reduces friction to facilitate movement of assimilates

Question 36

companion cells: Each sieve tube element has companion cell to

Answer 36

**control metabolism** of associated sieve tube member load+**unload sugars**

Question 37

features of companion cell - nucleus +other organelles - transport proteins in plasma membranes - large numbers of mitochondria - plasmodesmata

Answer 37

- provide metabolic support to sieve tube elements- helps with loading+unloading of assimilates - moves assimilates in+out sieve tube elements - provides ATP for active transport of assimilates -allowing organic compounds to move from the companion cells into the sieve tube elements

Question 38

transpiration

Answer 38

loss of water from LEAVES/ STEM

Question 39

xerophytic

Answer 39

adapted to dry conditions- adaptations maximise water conservation

Question 40

fleshy succulent leaves

Answer 40

stores water for times of low availability

Question 41

hinge cells shrink when flaccid

Answer 41

leaves roll, exposing thick cuticle to air, creating humid space in middle of leaf

Question 42

leaves reduced to thin needles

Answer 42

reduces SA so reduced transpiration

Question 43

stomata close during light, open at night

Answer 43

daytime water loss minimised CO2 fixed at night

Question 44

source of assimilates

Answer 44

- green leaves+stem - storage organs (tubers+roots) - food stores(germinating seeds)

Question 45

sinks could be

Answer 45

- meristems actively dividing - growing roots/actively absorbing mineral ions - any part of plant where assimilates are being stored