Identify the chemicals produced by Calotropis that provide defense against grazers and browsers.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Cardiac glycosides
Many plants make poisonous chemicals as a defence against herbivores, the animals that graze and browse on them. The weed Calotropis makes highly poisonous cardiac glycosides. This is why cattle and goats are never seen browsing on it.
(1) Strychnine — Incorrect. It is also a plant defence chemical, but it is made by the Strychnos tree, not by Calotropis.
(2) Quinine — Incorrect. It is the defence chemical of the Cinchona tree. It is used to treat malaria.
(3) Cardiac glycosides — Correct. They are the poisons that protect Calotropis from grazers.
(4) Caffeine — Incorrect. It is made by plants such as coffee and tea, not by Calotropis.
NCERT Extract:
Population Interactions – “… Many plants produce and store chemicals that make the herbivore sick when they are eaten, inhibit feeding or digestion, disrupt its reproduction or even kill it. You must have seen the weed Calotropis growing in abandoned fields. The plant produces highly poisonous cardiac glycosides and that is why you never see any cattle or goats browsing on this plant.”