Leaf structure (Plant nutrition)

Question 1

How leaf is adapted for photosynthesis

Answer 1

1. Petiole
2. Thin broad lamina
3. Waxy cuticle on upper and lower epidermis
4. Stomata present in epidermal layers (mainly underside)
5. Chloroplasts containing chlorophyll in all mesophyll cells
6. More chloroplasts in upper palisade tissue
7. Interconnecting system of air spaces in spongy mesophyll

Question 2

Petiole (adaptation)

Answer 2

• hold leaf in position

- absorb max light energy

Question 3

Thin broad lamina (adaptation)

Answer 3

• short diffusion distance for gaseous exchange
• enables light to reach all mesophyll cells
• large SA, max absorption of light

Question 4

Waxy cuticle on upper and lower epidermis (adaptation)

Answer 4

• reduce water loss thru evaporation frm leaf

- transparent: allow light to enter leaf

Question 5

Chloroplasts containing chlorophyll in all mesophyll cells

Answer 5

• chlorophyll absorbs, converts light energy to chemical energy
• used to make glucose

Question 6

More chloroplast in upper palisde tissue

Answer 6

• more light energy absorbed near leaf surface

Question 7

Interconnecting system of air spaces in spongy mesophyll (adaptation)

Answer 7

• rapid diffusion of CO2 and O2 into and out of mesophyll cells

Question 8

How guard cells control size of stomata (sunlight)

Answer 8

• guard ells photosynthesise
• convert light energy to chemical energy
• chem energy used to pump K+ ions from neighbouring epidermal cells into guard cell
• guard cell wp falls
• water from neighbouring epidermal cells move in via osmosis
• increase guard cell turgidity, become swollen
• guard cells thick cell wall on one side of cell (side arnd stomatal pore)
• swollen gc become more curved, pull stoma open

Question 9

How guard cells control size of stomata (night)

Answer 9

• K+ ions accumulated in gc during day diffuses out
• wp of gc rises
• water leaves gc via osmosis
• gc become flaacid, stoma closes
• also when weather v hot, excessive rate of evaporation, gc become flaccid)

Question 10

How CO2 enter leaf

Answer 10

• CO2 used during photosynthesis in presence of light, rapidly used up
• CO2 conc lower than atmospheric air
• diffusion gradient exists
• CO2 diffuses frm surrounding air thru stomata into air spaces of leaf
• surfaces of mesophyll cells covered by thin film of water, CO2 can dissolv in it
• dissolved CO2 diffuses into cells

Question 11

Xylem transports water and mineral salts into leaf

Answer 11

• water and mineral salts move from cell to cell thru mesophyll of leaf