Apoplastic pathway is blocked at endodermis by:
C fits best: Casparian strip. Keep the WATER TRANSPORT basics straight and Casparian strip stands out as the precise answer. Avoid: A) Suberin lamella; B) Middle lamella; D) Plasmodesmata. Light and flowering items often hinge on which photoreceptor or day-length rule is in play.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.