Answer:
Light was a limiting factor for photosynthesis under the given conditions. Light is required for photosynthesis.
Explanation:
According to Blackman's principle of limiting factors, the rate of photosynthesis is regulated by the factor which is present below the minimal value. Photosynthesis is regulated by many factors such as CO2 concentration, temperature, light intensity, etc. However, under particular conditions, the factor present below the minimum levels regulate its rate.
In the experiment, when the light intensity was present below its minimum levels, an increase in the light intensity increased the rate of photosynthesis. Here, light intensity was the limiting factor and no other factors such as CO2 or temperature would affect the rate of photosynthesis.
Once the light intensity reaches its optimal levels, other factors become limiting and there is no further increase in the rate of photosynthesis by increasing the light intensity.