Secondary metabolites such as nicotine, strychnine and caffeine are produced by plants for their:

Solution & Explanation

Answer: (A) Defence action. Solution: Nicotine, strychnine and caffeine are alkaloids, which are secondary metabolites. While NCERT notes that many secondary metabolites are useful for human welfare and some have ecological importance, these alkaloids are produced by plants chiefly for defence (deterring herbivores and pathogens). Hence the correct functional role here is defence action. NCERT Reference: Ch 9, p.108, line ~24 — "Some secondary metabolites have ecological importance." (Extension: the defence role of plant alkaloids is the ecological function implied here; NCERT names morphine, codeine, etc. as alkaloid secondary metabolites in Table 9.3, p.108, line ~47.)