Question

What is phytochrome? How does it differ from chlorophyll and cytochrome? Give a brief account of phytochrome mediated processes in plants.

Answer 1

Hint:Light has a profound effect on the growth and development of plants. Light acts as a signal to initiate and regulate photomorphogenesis (light-mediated changes in plants independent of photosynthesis). There are certain pigments in plants that are responsible for this process to perform an action. Signals for light are photoreceptors.

Complete step by step answer:Phytochrome is a photomorphogenic pigment that absorbs red and far-end light and causes photomorphogenesis. It absorbs blue light. This pigment is found in most plants where the sole purpose is to regulate and developmental processes. These include-
Leaf abscission (detachment of leaves), Seed germination, Stem elongation, Chloroplast development (not chlorophyll synthesis), etc.
These are also found in bacteria and fungi.
Chlorophyll is the green pigment found in plants that absorbs light and hence leads to photosynthesis and Cytochrome are the proteins found in plants according to their function. They are found as globular and membrane proteins. The main function is involved in the electron transport system.
There are different processes mediated in plants such as-
1. Fast responses- These happen inside a time interval of seconds to minutes.
2. Slow responses- These include slow reactions that take hours to days to show themselves. Slow reactions like seed germination, hypocotyl prolongation, leaf extension, abscission, blooming, fruiting have been demonstrated to be under phytochrome control. A portion of the moderate reactions constrained by phytochrome is-
a. Inversion of red light animated seed germination by a long shot red light.
b. Exhibit of control of internodal extending by phytochrome, the impacts were seen following eight days. The plants kept in the light-dull cycle got either R or FR light and so on.

Note:Phytochrome, Chlorophyll, and Cytochrome are found in plants as pigments. Phytochrome is a photomorphogenic pigment, Chlorophyll is a green pigment and cytochrome is present as a protein according to the structure. Phytochrome pigment is found to be present in two photoreversible forms. It is responsible for chlorophyll development but not for chlorophyll synthesis.