Question

Phytoalexins are toxins, like antifungal or fungi static substances produced by the host as defensive measure after infection and are generally
(A) Lipids
(B) Glycoproteins
(C) Phenolic compounds
(D) Proteins

Answer 1

Phytoalexins are toxic substances produced by the plants in response to the infection. Apart from antifungal property, it exhibits anti-microbial and anti-oxidative properties as well. Usually, the compounds produced by plants are made of phenols, tannins, etc. They are often classified under phytochemicals that are involved in the plant's defence mechanism.

Complete answer:
Phytoalexins are produced by hosts, usually plants which are antimicrobial and anti-oxidative in nature. They are produced in response to any infection and are often accumulated at the site of infection. These are considered as broad spectrum inhibitors whose property varies according to the plant species. Phytoalexins are classified under several classes including phenols, terpenoids, alkaloids, etc. based on the chemical nature. They inhibit the microbial infection by disrupting their cell wall, growth and metabolism. Moreover, it has the ability to prevent reproduction of the infectious microbe.
Phytoalexins are produced by the plants even when they are under continuous stress like draught, high salt conditions, etc. Most of the phytoalexins are phenolic compounds which contain hydroxylated aromatic rings. High levels of polyphenols or phytoalexins are produced in certain wood, as a way of naturally preserving the wood against rot.

Hence the correct answer is option(C)

Note: The easy way to remember is that most of the substances which are produced by plants contain phenolic compounds or simply polyphenols. Usually phenolic compounds are a part of a plant's defence mechanism which possess anti-fungal, anti-microbial, anti-oxidative and anti-cancerous properties naturally.