Calotropis, a weed growing in abandoned fields, produces one of the following biochemicals as a defense against grazers and browsers:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Cardiac glycosides
Plants cannot run away from herbivores, so many have chemical defences: substances that make the animal sick or even kill it.
Option (1) Nicotine — Incorrect. Nicotine comes from the tobacco plant. It is also a defence chemical, but not the one Calotropis makes.
Option (2) Opium — Incorrect. Opium comes from the latex of the poppy plant, Papaver somniferum.
Option (3) Cardiac glycosides — Correct. Calotropis makes highly poisonous cardiac glycosides. That is why cattle and goats never browse on it.
Option (4) Strychnine — Incorrect. Strychnine is a poison from the seeds of Strychnos plants, not from 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.”