Cytokinins are plant growth promoters that mainly help cell division (cytokinesis) and delay the ageing (senescence) of leaves. They are made where cells divide fast: root tips, developing shoot buds and young fruits. Memory hook: "Cyto-KIN-esis KEEPS leaves young" — cytoKINins do KINesis (cell division) and KEEP leaves fresh by moving nutrients to them.
Cytokinins are made in regions of rapid cell division (root apices, shoot buds, young fruits). They drive cell division, form new leaves and chloroplasts, overcome apical dominance, and delay leaf senescence by mobilising nutrients toward the leaf.
Your doubts, answered
Does cytokinin promote or delay senescence? This confuses me.
Cytokinin DELAYS senescence (delays leaf ageing). It does this by promoting nutrient mobilisation — it pulls nutrients toward the leaf, so the leaf stays green and healthy for longer. Do not mix it up with ethylene, which PROMOTES senescence and abscission. This exact point was asked in NEET 2025.
Is kinetin the same as cytokinin? Is it natural?
Kinetin was the first cytokinin discovered (from autoclaved herring sperm DNA) and it is a modified form of adenine (a purine). But NCERT clearly states kinetin does NOT occur naturally in plants. The natural cytokinin is zeatin, isolated from corn kernels and coconut milk. So kinetin = synthetic/lab, zeatin = natural.
Where are cytokinins synthesised in the plant?
In regions of rapid cell division: root apices (root tips), developing shoot buds and young fruits. This is a common NEET fact — remember cytokinins are made where cells are dividing fast, matching their cell-division function.
How does cytokinin overcome apical dominance while auxin causes it?
Auxin from the shoot tip suppresses the growth of lower (axillary/lateral) buds — this is apical dominance. Cytokinins do the opposite: they promote lateral shoot growth and help axillary buds grow, so they overcome apical dominance. They are antagonistic here.
Why do you add both auxin and cytokinin in tissue culture?
The auxin-to-cytokinin RATIO decides organ formation from callus. A balanced combination of auxin and cytokinin induces both shoots and roots. High cytokinin favours shoots, high auxin favours roots. NEET 2016 asked exactly this — the answer was auxin and cytokinin.
⚠️ The NEET trap ✗ Cytokinin promotes senescence and abscission of leaves. ✓ Cytokinin DELAYS leaf senescence (via nutrient mobilisation). ETHYLENE is the one that promotes senescence and abscission. 🧠 Cytokinin = keeps leaves young. Ethylene = ages and drops leaves. Swap them in your head and you will lose an easy mark.
Real NEET questions
NEET 2025
Which one of the following phytohormones promotes nutrient mobilization which helps in the delay of leaf senescence in plants?
A · Gibberellin
B · Cytokinin ✓
C · Ethylene
D · Abscisic acid
Solution: Cytokinins promote nutrient mobilisation, which pulls nutrients toward the leaf and so delays leaf senescence. Gibberellins delay senescence but by a different route, ethylene actually promotes senescence and abscission, and ABA is a stress hormone/inhibitor. NCERT: cytokinins 'promote nutrient mobilisation which helps in the delay of leaf senescence'.
NEET 2016
You are given a tissue with its potential for differentiation in an artificial culture. Which of the following pairs of hormones would you add to the medium to secure shoots as well as roots?
A · IAA and gibberellin
B · Auxin and cytokinin ✓
C · Auxin and abscisic acid
D · Gibberellin and abscisic acid
Solution: In plant tissue culture, the auxin-to-cytokinin ratio decides organ formation. A balanced combination of auxin and cytokinin induces both shoot and root differentiation from the callus. Gibberellin and ABA are not used for this, and ABA is an inhibitor, so the other pairs are wrong.
Solved Plant Growth and Development NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Cytokinins mainly promote cell division (cytokinesis). They also help produce new leaves, chloroplasts in leaves, lateral shoot growth and adventitious shoots, overcome apical dominance, and delay leaf senescence through nutrient mobilisation.
Which is the natural cytokinin?
Zeatin is the natural cytokinin, first isolated from corn kernels and coconut milk. Kinetin, though discovered first, does not occur naturally in plants.
How do cytokinins delay senescence?
They promote nutrient mobilisation — nutrients are moved toward the leaf, keeping it green and functional, which delays the leaf's ageing (senescence).
Do cytokinins overcome apical dominance?
Yes. Cytokinins promote lateral shoot growth and help axillary buds grow, so they overcome the apical dominance caused by auxin.
Is cytokinin a growth promoter or inhibitor?
Cytokinin is a growth promoter, along with auxins and gibberellins. Abscisic acid is the main inhibitor, and ethylene is largely an inhibitor of growth.
