7. transport in flowering plants

Question 1

relate the structure of xylem cells to their function

Answer 1

transports water from soil to stems and leaves
- long hollow continuous tube
- no cross walls to allow easy flow of water
- lignin in walls - prevent cell from collapsing

Question 2

relate the structure of phloem cells to their function

Answer 2

carry food products from leaves to other parts of the plants
- sieve tubes and cells with cross walls so substances can pass from one cell to another

Question 3

outline the pathway taken by water through the root

Answer 3

1. water is absorbed from the soil through root hair cells by osmosis
2. travels through root cortex cells by osmosis from cell to cell
3. reaches xylem vessels in the middle of root
4. xylem transports it through stem and into mesophyll cells

root hair –> root cortex –> xylem –> mesophyll cells

Question 4

describe ‘transpiration’

Answer 4

the loss of water vapor from leaves.
water vapor evaporates from the surface of the mesophyll cells into air spaces then diffuses out of the leaves through the stomata as water vapor

Question 5

explain the effects of wind speed on transpiration rate

Answer 5

slight wind blows away water vapor around leaves which increases transpiration rate but strong winds reduces transpiration rate due to closing of stomata to reduce water loss

Question 6

explain the effects of temperature on the rate of transpiration

Answer 6

increase in temperature causes an increase in transpiration rate because more heat is available to evaporate water

Question 7

explain the effects of light intensity on transpiration rate

Answer 7

light intensity increases the rate of transpiration as light increases temperature as well as causes opening of stomata

Question 8

explain the effects of humidity on transpiration rate

Answer 8

lower atmospheric humidity outside leaf increases transpiration rate because of difference in gradient which causes faster diffusion of water vapor

Question 9

explain how wilting occurs

Answer 9

wilting occurs when the rate of transpiration is higher than the rate of water uptake which results in loss of turgor pressure in plants causing cells to become flaccid and plasmolyzed

Question 10

explain the mechanism by which water moves upwards in the xylem vessels

Answer 10

when water is taken up from the xylem it creates a tension called transpiration pull which is transmitted all along the xylem vessel and the water in the xylem vessels is continuous and does not break because of the cohesive force of attraction between water molecules

Question 11

describe ‘translocation’

Answer 11

the movement of sucrose and amino acids from parts of plants that make them to parts of plants that use or store them

Question 12

state the function of xylem

Answer 12

transport of water and mineral ions

Question 13

relate structure of xylem to their function

Answer 13

1. thick walls with lignin
2. no cell contents
3. cells joint end to end with no cross walls to form long continuous tube