Question

Emerson’s enhancement effect and Red drop have been instrumental in the discovery of:

• A. Photophosphorylation and non – cyclic electron transport
• B. Two photosystems operating simultaneously
• C. Photophosphorylation and cyclic electron transport
• D. Oxidative phosphorylation

Answer 1

The correct option is B Two photosystems operating simultaneously

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. This effect was first of all noticed by Robert Emerson of Illinois University.
Later on Emerson and his group observed that if chlorella plants are given the inefficient far red light and red light of shorter wavelengths in alternate fashion, the quantum yields were greater than could be expected from adding the rates found when either colour was provided alone. This synergistic effect or enhancement is known as Emerson enhancement effect.
This was the first good evidence that there are two photo systems; one absorbs far red light and other red light and both of them must operate to drive photosynthesis most effectively.