Plants harness the energy in sunlight to make sugars from carbon dioxide and water. This process is called photosynthesis. A number of environmental factors affect the rate of photosynthesis. These are:

Light Wavelength: Red and blue wavelengths are most effective for photosynthesis. Green (500nm) is least effective.

Light Intensity: Photosynthesis is faster in more intense light until limited by some other factor. Once the reactions are going as fast as they can, more intense light has no effect.

Humidity: If the humidity is low, the stomata will close to reduce water loss through transpiration. Closed stomata limit gas exchange, and photosynthesis is slowed by a reduction in carbon dioxide availability.

Temperature: The rate of photosynthesis increases with temperature. Above the optimum temperature for photosynthetic enzyme function, photosynthesis is inhibited or shut down completely.

Carbon Dioxide Concentration: More carbon dioxide in the air allows more photosynthetic conversion into sugar, until limited by another factor.

Water: Compared to the amount of water needed to sustain a plant, the amount needed for photosynthesis is small. However, a dehydrated plant cannot perform efficient photosynthesis.