The photoreceptor involved in photoperiodism is:
Answer: C) Phytochrome. For PHOTOPERIODISM, remember the key idea and you’ll land on this option; the distractors usually swap cause and effect or confuse similar terms. Avoid: A) Chlorophyll; B) Carotenoid; D) Cryptochrome. Name the process first, then pick the option that describes it — don’t reverse cause and effect.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.