Question

The pigment involved in red-far red light interconversion is
A) Cytochrome
B) Xanthophyll
C) Lycopene
D) Phytochrome

Answer 1

Hint: Plants have photoreceptors, which are basically proteins that are specially designed to perceive light and produce certain biological effects in the plant. These proteins can detect different types of wavelength as plants use different types of wavelength for different purposes.

Complete Answer:
Phytochromes are chromoproteins which act as photoreceptors. They help in developmental processes and are involved in photoplasty, chlorophyll-synthesis, seedling-elongation and also govern the shape, size, count and leaf movement. They are involved in photomorphogenesis too. The phytochrome is a protein which is covalently bonded to a chromophore. These wavelengths are detected by the phytochrome receptors. Phytochrome exists in two forms-Pfr and Pr: P biologically active form is the Pfr and absorbs far-red. It is converted to Pr when far-red light is absorbed. Pr absorbs red wavelengths. Pr is converted to Pfr when red light is absorbed.
Cytochrome, are a group of hemoprotein cell components that can undergo reduction and oxidation (gain and loss of electrons) with the aid of enzymes.
Xanthophyll is an accessory pigment which absorbs the wavelength that chlorophyll cannot absorb and provides yellow pigment to the leaves.
Lycopene is a bright red carotenoid hydrocarbon with antioxidant properties. It's the pigment which gives colour to tomatoes and watermelon.

So the correct answer is Option D.

Notes:
A plant has the following types of photoreceptors:
1. Phytochrome
2. Cryptochrome
3. Phototropin
4. UVR8
Photomorphogenesis is the process of development of plants in accordance with the plant spectrum of light.
The plant responds to light signals in the following two ways:
1. Phytochrome-mediated photoresponse
2. Blue-light response or cryptochrome-mediated photoresponse