Plants

• Waxy cuticle is transparent allowing light through, prevents water loss
• Chloroplasts carry out photosynthesis and maintain steep diffusion gradient
• Spongy mesophyll has short diffusion distance and large surface area
• Air space in the spongy mesophyll increase contact with gases
• Stomata increase area for gas exchange
• Guard cells control opening/closing of stomata
• Guard cells are open when the cell is turgid
• Guard cells lose water through osmosis, become flaccid and close the stoma
• Stomatas closing prevents further water loss
• Compensation point is when the rate of photosynthesis is equal to the rate of respiration
• In the day the rate of photosynthesis is higher than respiration
• At night the rate of respiration is higher than photosynthesis