Planty bits (:

Dicotelydon - 2 cotelydon- two seed leaf
Monocotelydon - one seed leaf.
In a plant, water and CO2 go in, and glucose and oxygen out go out. Oxygen and carbon dioxide are the gas exchange products.

Photosynthesis takes place in daylight hours.

Respiration takes place all the time, as all cells need to respire.

Stoma (singular)
Stomata (plural)

- Large surface area = numerous stomata.
- Thin= Short diffusion distance.
- Concentration gradient is great.

Spongy mesophyll, lots of air spaces.

Layer of moisture, gas dissolves and gas diffuse through membrane.

Vascular bundle, where xylem and phloem are. Xylem brings water into the leaf.

Gases enter the leaf through the stomata, usually in the lower surface. Stomata are enclosed by guard cells that can swell up and close the stomata to reduce water loss. The gases then diffuse through the air spaces in the leaf which are in direct contact with the spongy pallisade mesophyll cells. Plants do not need a ventilation mechanism as their leaves are exposed, so the air surrounding them is constantly being replaced.
During the hours of daylight, photosynthesis increases the oxygen concentration in the sub-stomal airspaces.
When a green plant is expose to bright light, both photosynthetic and respiritory gas exchange are taking place in the leaves. However, since the rate of photosynthesis exceeds the rate of respiration during the day, there is a net uptake of carbon dioxide and release of oxygen.
In the dark, the non photosythetic parts of the plant, that respire, there is a net uptake of oxygen and a net release of carbon dioxide.

• Long thin pallisade cells, large Surface Area.
• loosely packed, whole surface covered.
• moist layer, gases can dissolve and diffuse easily.
  
• air spaces give a constant circulation of air.
  
• thin - short diffusion distance.
  
• numerous stomata.