Question

Write notes on
(a) Emerson enhancement effect

(b) Warburg effect

(c) Red drop

(d) Photorespiration.

Answer 1

a. The Emerson effect is the increase in the rate of photosynthesis after chloroplasts are exposed to the light of wavelength 680 nm (deep red spectrum) and more than 680 nm (far red spectrum). When simultaneously exposed to a light of both wavelengths, the rate of photosynthesis is far higher than the sum of the red light and far-red light photosynthesis rates.

b. The Warburg effect is the decrease in the rate of photosynthesis due to high oxygen concentrations. Oxygen is a competitive inhibitor of carbon dioxide fixation by RuBisCO which initiates photosynthesis. Furthermore, oxygen stimulates photorespiration which reduces photosynthetic output.

c. Red Drop Effect: Wavelengths beyond 700nm are apparently of insufficient energy to drive any part of photosynthesis. So a huge drop in efficiency has been noticed at 700nm. This phenomenon is called as RED DROP EFFECT. In other words, there is a sharp decrease in quantum yield at wavelengths greater than 680nm.

d. Photorespiration: a respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis.