How plants turn sunlight into food.
Select a card to see the details.
The energy source
Chlorophyll absorbs mostly red and blue-violet light and reflects green, which is why leaves look green.
More light means faster photosynthesis, up to the light saturation point, where the rate levels off.
The carbon source
It enters through stomata on the underside of the leaf. When stomata close, for example at midday in dry weather, photosynthesis slows sharply.
The source of hydrogen and electrons
Roots absorb it and xylem carries it to the leaves. All the oxygen released in photosynthesis comes from water, not from carbon dioxide.
On the thylakoid membranes
Water is split and oxygen is released. ATP and NADPH are produced to power the next stage.
In the stroma
ATP and NADPH are used to fix carbon dioxide and reduce it to sugar. It does not need light directly, but it depends on the products of the light reactions.
Where does the oxygen released in photosynthesis come from?
The light reactions split water, and that is where the oxygen comes from. The carbon and oxygen of carbon dioxide end up in the sugar.
Why do growers cool their greenhouses at night?
At night there is no photosynthesis, only respiration using up stored sugars. Lower temperatures slow respiration.