The rate of photosynthesis is now constant and increasing
light will not increase the rate of photosynthesis.
At this point, light is no longer limiting the rate. Another
factor (eg. carbon dioxide being in low supply) is now
limiting the rate of photosynthesis.
As light intensity increases, so does the rate of
photosynthesis. This is because the chlorophyll can absorb
more light so there is more energy for the chemical reaction
to take place.
This graph depicts that in the beginning, when carbon
dioxide concentrations were low, it was a contributing factor
to the rate of photosynthesis; however at some point when
there is a higher concentration of carbon dioxide, the rate of
photosynthesis becomes constant and concentration stops
being a limiting factor because there is enough carbon
dioxide for the plant to perform its respiratory and
generational functions.
As a result, another factor has taken over (eg. Temperature
being high) to become limiting to the rate of photosynthesis.
At the higher temperature, the rate of photosynthesis
increases which means that the temperature was at some
point a limiting factor because an increase in temperature
allows the molecules in the plant to gain kinetic energy which
helps to excite the electrons in the chlorophyll molecules in
the plant and overall increase the rate of photosynthesis.
However, at the peak of the graph where the temperature is
considered too high for the plant and the enzymes start to
break down, the rate of photosynthesis begins to decrease
again as the temperature continues to increase.
