Question

The rate of photosynthesis is maximum in which colour of light?
A. In the green light
B. In the red light
C. In the yellow light
D. In purple light

Answer 1

Photosynthesis is the process of energy production by plants utilizing sunlight, carbon dioxide, and water. Light in the wavelength range of 680 to 700 nm shows an increased rate of photosynthesis. Other factors that affect the rate of photosynthesis are temperature, climate, and water availability.

Complete answer: Photosynthesis is a biological process of energy production by converting light energy into chemical energy. The light source for photosynthesis is sunlight and this light reaction takes place in the grana of the chloroplast. The light gets converted into ATP which is an energy molecule along with NADPH. The chlorophyll pigment in the chloroplast is the key unit that absorbs the light in the visible light spectrum. The visible light ranges from 380 nm to 760 nm. Chlorophyll is more sensitive to absorb blue light and red light. When exposed to red and blue light, plants show an increase in the rate of photosynthesis. The green light shows the minimum effect on the rate of photosynthesis. But the maximum sensitivity of chlorophyll is towards red light which ranges between 680 nm to 700 nm wavelengths. This has been proven by the Emerson enhancement effect which states that the rate of photosynthesis increases on exposure to red light. The range included 680 nm which indicates deep red light and 700 nm which indicates far-red light. The P680 and P700 photopigments of chloroplast absorb actively in these regions of wavelength.
Hence, the correct answer is option B.

Note: The Cyanobacteria also perform photosynthesis but as they reside several meters underwater, they are not able to receive the right wavelength. Correct wavelength is required for photoinduced charge separation in photosynthetic pigments. A series of proteins having different pigments surround the reaction centre in Cyanobacteria to combat this problem.