Transport in plants

Question 1

Functions of the xylem

Answer 1

-Transport of water and minerals
-Provides mechanical support

Question 2

Describe the structure of xylem vessels

Answer 2

-Made up of cells end to end, lignified cellulose cell wall which is impermeable to water and solutes. Contain pits (that have no lignin)

Question 3

What is meristem tissue?

Answer 3

Found in the root and shoot tips and in the cambium of the vasculr bundles. It is an area of undifferentiated cells which can divide and differentiate into other cell types.

Question 4

What is mass flow?

Answer 4

The bulk transport of material from one point to another as a result of pressure differences between two points

Question 5

Pure water has a water potential of …

Answer 5

0

Question 6

What is the importance of water in plants?

Answer 6

-evaporative water loss cools plants
-mineral ions and photosynthetic products are transported in aqueous solution
-water is a raw material for photosynthesis
osmosis provides turgor pressure which provides a hydrostatic skeleton to support stems and leaves

Question 7

How are root hair cells adapted for their function?

Answer 7

-have a large surface area and thin walls to provide a short diffusion distance
-contain many mitochondria to provide ATP for active transport
-High solute concentration to maintain high water potential gradient
-contain many different solutes to lower the water potential so water moves in by osmosis

Question 8

What are the two pathways water can take between cells?

Answer 8

-Apoplast pathway- cell walls
-Symplast pathway - cell membrane, cytoplasm

Question 9

What factors affect rate of transpiration?

Answer 9

-no. leaves - more leaves = more stomata so more water loss
-no., size and position of stomata
-presence of waxy cuticle- thicker waxy cuticle = slower rate of transpiration
-light intensity
-temperature - higher temperatures there is faster rate of evaporation from cell surface
-relative humidity - higher humidity = less of a water potential gradient for evaporation
-wind

Question 10

What apparatus do you use to measure the rate of transpiration?

Answer 10

Potometer

Question 11

What are the precautions when using a potometer?

Answer 11

1. cut shoot under water and at an angle (so no air bubble)
2. make sure to choose healthy shoot
3. insert shoot into capillary tube ander water (air tight)
4. put vasaline around joints (water tight)
5. make sure leaves dont get wet
6. introduce an air bubble
7. leave to acclimatise
8. use a syring to reset air bubble