Factors Affecting the Rate of Photosynthesis

Contributed by:
Sharp Tutor
This presentation will discuss the factors that affect the rate of photosynthesis. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities.
2. 1) LIGHT
As light intensity increases, the
rate of photosynthesis initially
increases, and thereafter, levels
off to a plateau.
3. • This plateau represents the maximum rate of
photosynthesis ---as seen in the diagram.
• Higher light intensity initially causes more
electrons in the chlorophyll molecules to become
excited (gain energy).
Modern Biology (Holt)
4. • As more and more electrons are excited, the
light reactions occur more rapidly.
• At a certain light intensity, however, all the
available electrons are excited and a further
increase in light intensity will not increase
the rate of photosynthesis.
Modern Biology (Holt)
5. 2) Carbon dioxide
Like increasing light intensity, increasing levels
of carbon dioxide around the plant stimulates
photosynthesis until it reaches a plateau. This
graph would resemble that of light intensity.
Modern Biology (Holt)
6. 3) Temperature
a) Raising the temperature accelerates
various chemical reactions of
photosynthesis. As a result, the rate of
photosynthesis increases, over a certain
Modern Biology (Holt)
7. • b) The rate of photosynthesis generally
peaks at a certain temperature, as seen
in the graph.
• c) Above this temperature, the rate
8. d) As the temperature increases, the stomates
begin to close, to limit water loss. This will have
the effect of stopping the carbon dioxide from
entering the leaf. This will also decrease the
rate of photosynthesis. (Also: Enzymes do not
function well at too high a temperature.)
9. 4) Water
• A lack of water will also slow the rate
of photosynthesis. Stomata can close
from water loss.
• Plants such as the cactus have
adaptations to prevent water loss in
dry, desert climates.