8. Transport In Plants

Question 1

State the function of xylem and phloem

Answer 1

xylem – transport of water and mineral ions,
and support
(b) phloem – transport of sucrose and amino
acids

Question 2

Now are xylem vessels adapted

Answer 2

The walls with lignin- very strong helps keep the plant upright
No cell contents - water can flow easily
Cells joined end to end with no cross walls - to form a long continuous tube

Question 3

Identify in images xylem and phloem

Question 4

Function of root heir cell

Answer 4

To absorb water and mineral ions from the soil

Have long root hairs which increase the surface area-increasing the water uptake by osmosis and absorption of mineral ions by active transport

Question 5

Outline the pathway of water

Answer 5

’ Root hair cell> root cortex cells > xylem> mesophyll cells

water enters the root by osmosis

Travels by osmosis through the cortex cell by cell,
some water also seeps in between

water reaches thw xylem cell and is drawn upwards because pressure at the top is low, & at the bottom is high so water therefore flows up

xylem carries water upto the mesophyl cell

Question 6

Describe transpiration

Answer 6

• loss of water vapour from leaves,.

Question 7

Continuation of water pathway

Answer 7

water evaporates from the surfaces of
the mesophyll cells into the air spaces and then
diffuses out of the leaves through the stomata as
water vapour

Question 8

Water vapour loss is related to

Answer 8

Large internal surface area provided by the interconnecting air spaces between mesopyll cells
Size and number of stomata

Question 9

Explain the mechanism by which water moves upward in xylem

Answer 9

Transpiration pull draws up a coloumu of water molecules held together by forces of attraction between water molecules

Question 10

Explain the conditions that affect transpiration rate

Answer 10

Temperature
Higher the temperature, increased vate of transpiration
greater kinetic energy
Water evaporating faster From surface of mesophyll
cells and diffusing faster out of the leaf

Wind Speed
Good air flow, increased rate of transpiration
the water evaporated is quickly moved away this creates a diffusion gradient between the leaf and the air

Humidity
hisher the humidity, slower the rate of transpiration
decreases the diffusion concentration gradient

Question 11

Explain how and why wilting occurs

Answer 11

if rate of transpiration is high, theres no limiting factor
• plant will loose water faster than it can take up
plant cells become flaccid, turgor pressure decreases, leaves become soft & floppy
this is called wilting

Question 12

Describe translocation

Answer 12

as the movement of
sucrose and amino acids in phloem from sources
to sinks

Question 13

Describe sources and sinks

Answer 13

sources as the parts of plants that release
sucrose or amino acids
sinks as the parts of plants that use or store
sucrose or amino acids

Question 14

Explain why some parts may acts as as source and sinks at different times

Answer 14

when a plant is actively photosynthesizing & growing
Leaves are the sources
roOts & flowers can be sinks (starch/)

During harsh seasons Iplant not grown leaves can’t photosynthesise
roots convert starch to sucrose - acts as
source
other parts of plant are now sinks