Plants

Question 1

Briefly describe gas exchange in a plant

Answer 1

Plants need co2 for photosynthesis and produce o2 as a waste gas
Gas exchange occurs at the surface of a palisade mesophyll cells. The cells are where most of the photosynthesis occurs

Question 2

Explain the adaptations for plants

Answer 2

Large surface area - large flat leaf and tall long palisade mesophyll cells
Short diffusion pathway- thin leaf and air spaces
Concentration gradient - mesophyll cells use the co2 maintaining low conc in cells and a concentration gradient

Question 3

What do stomata do and how do plants reduce water loss

Answer 3

Stomata can open (allow gasses through) and close (to reduce water loss)
The guards cells control the opening/closing of the somata
All plants can reduce water loss
-water can be lost through transpiration
Stomata can close when the guard cell becomes flaccid reducing water loss
The leaf is covered in hydrophobic , waxy cuticle which reduces water loss by evaporation
Most stomata are on the lower surface of leaf as this reduces evaporation

Question 4

Explain how xerophytes are adapted for hot dry conditions

Answer 4

• rolled leaf shape as upper epidermis is facing inwards to trap humid air
  -reduced surface area for transpiration
  Sunken stomata , humid air is trapped reducing water gradient
  No stomata exposed
  Thick waxy cuticle reducing evaporation