Which invasive alien weed, introduced into India as a contaminant in imported PL-480 wheat from the USA, produces airborne pollen that triggers severe chronic respiratory allergies (asthma and rhinitis)?

Answer and explanation

Correct answer: C. Parthenium hysterophorus (Carrot grass)

  1. Step 1: Parthenium hysterophorus (commonly called congress grass or carrot grass) arrived in India in the 1950s as a seed contaminant in imported wheat shipments.
  2. Step 2: It proliferates aggressively across open wastelands and disturbed soils.
  3. Step 3: Its abundant, lightweight pollen grains contain sesquiterpene lactones that cause severe allergic contact dermatitis, allergic rhinitis (hay fever), and bronchial asthma.
Answer
Parthenium hysterophorus (Carrot grass)
Why not the others: 'Eichhornia crassipes (Water hyacinth)' is an aquatic invasive macrophyte dubbed the 'Terror of Bengal' causing water choking and eutrophication, not airborne pollen allergy; 'Lantana camara' is an invasive toxic shrub; 'Prosopis juliflora' is an invasive thorny mesquite.

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