Transport In Plants

Question 1

Adaptations of Xylem

Answer 1

1. Hollow w/ no cross walls
   - Allows movement of water & dissolved mineral salts w/o obstruction
   ——
2. Narrow lumen
   - Allows water to rise up via capillary action
   ——
3. Walls of xylem thickened with lignin
   - Strengthens cell walls of xylem cells
   - SO Prevents collaspe
   - When bundled tgt, give mechanical support for plant

Question 2

Adaptations of phloem

Answer 2

1. Has companion cells w/ mitochondria
   - Comp cells can carry out aerobic respiration to release energy to load sugar from mesophyll cells into sieve tubes
   ——
2. Has sieve plates
   - To facilitate the movement of manufactured food substances

Question 3

Define transpiration

Answer 3

It is the evaporation of the thin film of moisture on the spongy mesophyll cells. It is also the diffusion of water vapour from a region of higher concentration in the intercellular air spaces of the leaf to a region of lower concentration outside the leaf

Question 4

Guards cells increasing size of stomata in presence of light

Answer 4

• In presence of light, chlorophyll containing chloroplasts in the guard cells convert light energy from the sun into chemical energy in the form of glucose
• This lowers the water potential of the guard cells
• Surrounding cells have a higher water potential than the guard cell
• Water molecules will move from the neighbouring cells to the guards cells through a partially permeable membrane, via osmosis
• Guards cells will have a higher WP & become turgid
• Size of stomata increases