- Which one of the following statements is correct for the transport of cytokinin in plants?
(1) It takes place only from root to shoot.
(2) it takes place only from shoot to root
(3) Root and shoot make their own cytqk,n, therefore. no transport is required.
(4) Transport can occur from root to shoot and vice versa.
Correct answer: (4) Transport can occur from root to shoot and vice versa.
Cytokinin is synthesized mainly in root apical meristems but also in various shoot tissues, and it is a mobile hormone. It moves upward from roots to shoots largely in the xylem (especially trans-zeatin–type cytokinins) and also downward from shoots to roots through the phloem (mainly iP- and cZ-type cytokinins). This bidirectional movement coordinates growth and development between above-ground and below-ground organs.
Explanation of options:
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(1) “Only from root to shoot” – incomplete. Root-to-shoot xylem transport is important but not exclusive; shoot-derived cytokinins also move to roots.
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(2) “Only from shoot to root” – also incomplete; it ignores well-established xylem transport from roots.
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(3) “Root and shoot make their own cytokinin, therefore no transport is required” – incorrect. Both organs can synthesize cytokinin, but long-distance transport is essential for systemic signaling and integration of environmental cues.
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(4) “Transport can occur from root to shoot and vice versa” – correct. Cytokinin is transported acropetally and basipetally via xylem, phloem, and cell‑to‑cell pathways.
