structure of a leaf

Question 1

what does the leaf having a large surface area and being thin mean for rate of photosynthesis?

Answer 1

• maximises absorption of sunlight by the photosynthetic cells
• increases number of stomata- carbon dioxide can diffuse quicker

Question 2

what does the upper epidermis being transparent do?

Answer 2

light can penetrate to the mesophyll

Question 3

the palisade cells are….

Answer 3

long, thin and tightly packed

Question 4

palisade cells contain large numbers of…
( what does this do for the rate of photosynthesis?)

Answer 4

• chloroplasts
• this maximises the absorption of sunlight energy

Question 5

where is the main site of photosynthesis?

Answer 5

the palisade mesophyll

Question 6

what does the stomata allow?

Answer 6

• gases to diffuse into the air spaces of the leaf
• provides a short diffusion distance for CO2

Question 7

what does the xylem do?

Answer 7

• transports water (absorbed in the roots) into the leaves
• provides a short distance for water to diffuse into the photosynthesising cells

Question 8

what does the phloem do?

Answer 8

• transports sugars made in photosynthesis to other parts of the plant

Question 9

what gases move into and out of the leaf?

Answer 9

• water vapour
• oxygen
• carbon dioxide

Question 10

water vapour is lost in…

Answer 10

transpiration

Question 11

what forms the stomata?

Answer 11

guard cells

Question 12

guard cells can change shape which does what for the stomata?

Answer 12

altering the size of the stomata

Question 13

when do the stomata close?

Answer 13

to reduce water loss and gas exchange

Question 14

what happens when the plant has lost too much water?

Answer 14

• the stomata close
• the guard cells become flaccid so the cell walls are not held apart and the stomata shrink

Question 15

what are stomata?

Answer 15

holes in the surface of the leaf

Question 16

where are stomata mainly found?

Answer 16

on the bottom surface

Question 17

what are on either side of the stomata?

Answer 17

two guard cells

Question 18

each guard cell has what type of cell wall on the stomatal side?

Answer 18

a thickened, inflexible, inner cell wall

Question 19

what happens when the guard cells photosynthesise?

Answer 19

• the concentration of sugars increase
• the water potential in the guard cells falls- water moves into the guard cells via osmosis
• they become turgid- causes guard cells to become banana shaped- due to the inflexible cell wall and opens the stomata

Question 20

what happens when photosynthesis stops in the dark?

Answer 20

• sugar concentration falls (due to respiration)
• water potential increases - water moves out of the guard cells
• guard cells become flaccid and the stomata close