Question

Red drop phenomenon and Emerson’s enhancement effect have been helpful in the discovery of

• A. photophosphorylation and non-cyclic electron transport
• B. two photosystems operating simultaneously
• C. source of oxygen released during photosynthesis
• D. oxidative phosphorylation

Answer 1

The correct option is B two photosystems operating simultaneously

Robert Emerson and Charlton Lewis illuminated the green algae with 680 nm and higher than 680 nm wavelength of light and and measured the amount of oxygen produced. This quantity was known as quantum yield.

Quantum yield is the number of oxygen molecules produced per photon absorbed.

They observed a sharp decrease in the number of oxygen molecules produced when the wavelength of light was higher than 680 nm, also known as the far-red region. This is known as the red drop phenomenon.

Emerson, later on, observed that when the green algae was illuminated by two beams of light simultaneously- one in the red region or 680 nm and other in far-red region or wavelengths greater than 680 nm, the rate of photosynthesis was greater than the sum of rates obtained when illuminated by each beam separately. This was known as Emerson enhancement effect.

This showed that photosynthesis is carried out by two photosystems which are functional at two different wavelengths and also that they are working in tandem.