Source organs during phloem translocation in healthy plants are:
That points to C: Mature leaves. Compared with the other options, Mature leaves is the one that correctly describes the PSS- Sec-F-Transport concept. The wrong ones are A) Roots; B) Developing fruits; D) Young leaves. If you’re stuck, eliminate anything that contradicts a basic fact you already know for this topic.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.