• Rates of photosynthesis are affected by a combination of environmental factors.Roine Magnusson/Photodisc/Getty Images
  
  Photosynthesis is the process of absorbing sunlight and converting it into sugars and oxygen. Green plants are the only structures that are able to accomplish this feat, and as such are the basis for all life on earth. The production of oxygen by green plants is what produced the conditions that allowed the appearance of animal life on Earth.
  
  

Nutrients

• Plants are able to convert sunlight into other elements and need sunlight to survive, however, they require other things as well. The levels of nutrients in the soil that the plant grows in will affect its health and vigor and has a limiting effect on its rate of photosynthesis if there are nutrients lacking in the soil. Healthy soil is produced by plants dying, rotting and composting back into the soil, so when there are a lot of plants growing in a location, that soil tends to be healthier and produce plants that can engage in high levels of photosynthesis.
  
  

Water

• Periods of drought will cause plants to wither and die if the adverse conditions continue for too long. Along with sunlight and soil nutrients, all plants require water to survive, although the amounts required by different plants can vary widely. Desert cacti and other succulents have meaty green leaves that can both store water and photosynthesize. These plants require far less water than broad leaved trees. A balance of rain and sun will lead to maximum photosynthesis by a green plant: rain to fill its water needs, and direct sunlight to allow it maximum opportunity for photosynthesis.
  
  

Temperature

• Every plant has an optimum temperature at which it will photosynthesize at a maximum rate. As the temperature drops below this level, or rises above it, rates of photosynthesis will decrease. If the temperature drops below or rises above the temperature that the plant is able to tolerate, the plant will die.
  
  

Light Levels

• Since photosynthesis is the direct conversion of sunlight into sugars and oxygen, the level of sunlight that a plant is exposed to will have the most direct effect on its levels of photosynthesis. During cloudy days, early mornings and late afternoons, photosynthesis will occur because there is sunlight present, but not at the same rate as when the plant is exposed to direct sunlight. Similarly, if a plant is growing in the shade, it will photosynthesize at a slower rate.