Question

The rate of photosynthesis is higher in
A. Very high light
B. Red light
C. Green light
G. Continuous light

Answer 1

Hint: Rate of photosynthesis depends on the wavelength of light. In the visible region of the electromagnetic spectrum, the rate of photosynthesis shows peaks at the two extreme colors of the spectrum.

Complete answer:
The colour of the leaves which we see is not due to a single pigment. This has been found by chromatographic separation. There are four pigments that are present in the leaves which give it its colour. These pigments are chlorophyll a, chlorophyll b, xanthophylls, and carotenoids. Chlorophyll a is bright or blue-green colour; chlorophyll b is yellow-green; xanthophyll is yellow and carotenoid is yellow to yellow-orange in colour.
The role of the pigments is to absorb light at specific wavelengths which is essential for the process of photosynthesis. Chlorophyll a is the chief pigment and other pigments act as accessory pigments. The first action spectrum of photosynthesis was given by T.W.Engelmann and it said that most of the photosynthesis occurred in blue and red regions of the spectrum. Some photosynthesis takes place at other wavelengths also but it is less.
Chlorophyll a being the chief pigment is responsible for trapping the light, and other pigments which are the accessory pigments also absorb light and transfer the energy to chlorophyll a.
Accessory pigments like chlorophyll b, xanthophyll, and carotenoid protect chlorophyll a from photo-oxidation and also enable a wider range of wavelengths of light which has to be utilized for photosynthesis. This light energy is utilized in the light reaction of photosynthesis also called the photochemical phase. These reactions include light absorption, water splitting, oxygen release, and formation of ATP and NADPH.
The formation of ATP and NADPH takes place by electron transport system in which proton gradient is created and then by chemiosmosis, the gradient is broken to release energy. The rate of photosynthesis is measured by the amount of oxygen released during the light reaction. Oxygen gas comes from the water molecule and not from the \[CO_2\] as was believed earlier.
Hence, the correct answer is option B.

Note: Chlorophyll and carotenoid pigments are present in chloroplast whereas xanthophyll pigment is present in chromoplast. Carotenoid and xanthophyll are fat-soluble pigments. These pigments are present inside the thylakoids.