induces highest rate of photosynthesis and green light induces lowest rate of photosynthesis. . Carbon dioxide CO is found only . % in the atmosphere but plays a vital role.
Increase in concentration of CO increases the rate of photosynthesis (CO concentration in the atmosphere is ppm). If concentration is increased beyond 500ppm, rate of photosynthesis will be affected showing the inhibitory effect. . Oxygen The rate of photosynthesis decreases when there is an increase of oxygen concentration.
This Inhibitory effect of oxygen was first discovered by Warburg ( ) using green algae Chlorella. . Temperature The optimum temperature for photosynthesis varies from plant to plant. Temperature is not uniform in all places.
In general, the optimum temperature for photosynthesis is o C to o C. This is not applicable for all plants. The ideal temperature for plants like Opuntia is o C, Lichens o C and Algae growing in hot spring photosynthesis is o C. Whether high temperature or low temperature it will close the stomata as well as inactivate the enzymes responsible for photosynthesis (Figure .
). In , Blackman put forth the importance of smallest factor. Blackman’s law of limiting factor is actually a modified Law proposed by Liebig’s Law of minimum . According to Blackman, “When a process is conditioned as to its rapidity by a number of separate factors, the rate of the process is limited by the pace of the lowest factor”.
To conclude in an easy way “at any given point of time the lowest factor among essentials will limit the rate of photosynthesis”. For example, when even sufficient light intensity is available, photosynthesis may be low due to low CO in the atmosphere. Here, CO acts as a limiting factor. If CO is increased in the atmosphere the rate of photosynthesis also increases.
Further increase in photosynthesis is possible only if the available light intensity is also increased proportionately (Figure . ). Factors affecting photosynthesis are further grouped into External or Environmental factors and Internal factors. I.
External factors: Light, carbon dioxide, temperature,