6.Cytokinin synthesis is maximum in
(1) Roots (2) Leaves
(3) Shoots tip (4) Fruits
Cytokinin synthesis is maximum in: (1) Roots.
Correct concept
In most vascular plants, cytokinins are synthesized primarily in the root apical meristems and other actively dividing root tissues. From there, they are transported via the xylem to shoots, leaves, buds, fruits, and seeds, where they promote cell division, delay senescence, and support sink strength.
So, the best single answer among the options is roots.
Explanation of each option
(1) Roots – Correct
-
Root tips contain actively dividing meristematic cells that express key cytokinin biosynthesis enzymes (such as IPTs).
-
Cytokinins produced here move upward in the transpiration stream and regulate shoot growth, bud activation, and leaf expansion.
-
That is why standard plant physiology texts state that the major site of cytokinin synthesis is roots.
(2) Leaves
-
Young leaves can synthesize some cytokinins, especially in their meristematic regions, but they are not usually the primary or maximum source.
-
Much of the cytokinin found in leaves has been transported from roots.
(3) Shoot tip
-
Shoot apical meristems also produce cytokinins and are important local sources for shoot and leaf development.
-
However, in most exam contexts, roots are emphasized as the main site of cytokinin biosynthesis, with shoot tips considered secondary sources.
(4) Fruits
-
Developing fruits and seeds often have high cytokinin concentrations, which promote intensive cell division and sink strength.
-
But a significant part of this cytokinin pool is supplied from roots; fruits are major targets and sometimes auxiliary sites, not usually cited as the maximal synthesis site in basic MCQs.
