Chapter 8 - Transport in plants

xylem

• transport of water and mineral ions, and support

• thick walls with lignin

• no cell contents

• cells joined end to end with no cross walls to form a long continuous tube'

• vascular tissue

phloem

transport of sucrose and amino acids

what are the characteristics of root hair cell?

• large surface area - increase uptake of water & mineral ions

• thin cell wall - easier transfer of water & nutrients by osmosis & active transport

pathway of water through root → stem → leaf

1. root hair cell

2. root cortex cells

3. xylem - moves up in a column

4. leaf mesophyll cells

Investigation: water movement in plants

1. place plant in beaker of water with colouring added

2. after few hours leaves of plant turns same colour as water - shows water taken up by plant

3. if cross section of plant cut, only certain areas of stalk stained (xylem)

transpiration

loss of water vapour from leaves

explain how transpiration works

• water evaporates from surfaces of mesophyll cells into air spaces

• diffuses out of leaves through stomata as water vapour

Explain how water vapour loss is related to

• large internal surface area from interconnecting air spaces between mesophyll cells

• size and num of stomata

translocation

movement of sucrose & amino acids in phloem from source to sink

source

parts of plants that release sucrose or amino acids

sinks

parts of plants that use or store sucrose or amino acids

explain why some parts of a plant may act as a source and a sink at different times [6]

1. leaf typically functions as a source when it is mature, producing sugars through photosynthesis.

2. sugars transported to different parts of the plant - act as sinks (roots/ fruits)

3. same leaf can become a sink during growth phase/during repair damage

4. requires energy & nutrients for its development - receives from other parts of the plant acting as sources.

5. shows plant's ability to adapt resource allocation based on developmental stage & environmental conditions

investigate Effect of Temperature & Wind Speed on Transpiration Rate

1. Set up the potometer in water & leave the tap for the reservoir of water open - prevent air bubbles entering equipment.

2. cut the stem of the plant at a slant under water - prevent air from entering the xylem & slant increase surface area where water is absorbed.

3. Lift potometer out of the water but leave the opening end of capillary tube submerged in the water - the water that will supply the plant.

4. Double check that the entire equipment is airtight and watertight. You don’t want any air bubbles or extra water interfering with your experiment.

5. Give time for the plant to adapt to new setting & pat dry its leaves.

6. Close tap for the reservoir of water.

7. Remove the capillary tube end from the water until one air bubble enters and then immediately place the capillary tube end back in the water.

8. Measure and record the starting position of the air bubble and start the stopwatch.

9. Time how long it takes the bubble to move a certain distance and calculate the rate of transpiration

effect of temp, wind speed, humidity on transpiration

• as temp increase, transpiration increase

• wind speed increase, transpiration increase

• humidity increase, transpiration decrease

explain effect of high humidity on stomata

• stomata will take longer to close

• reduced water vapour concentration

• guard cells lose less water and remain turgid, keeping stomata open longer.

cohesion

attraction between water and water

adhesion

attraction between water and xylem