Question

In callus culture, shoots can be induced by the supply of
A. Auxin and no cytokinin
B. Higher concentration of auxin and the lower concentration of cytokinin
C. Higher concentration of cytokinin and the lower concentration of auxin
D. Both auxin and cytokinin in equal amounts

Answer 1

Hint: For the growth of plants there are mainly five types of hormones required. from them, some are the promoter and some are inhibitors. but here we have to think about the function of only two I.e. cytokinin and auxin which both are growth promoters.

Complete answer:
AUXIN:
(1)Apical Dominance: In most higher plants, the growing apical bud inhibits the growth of the lateral buds, a phenomenon called apical dominance. Removal of shoot tips(decapitation) usually results in the growth of lateral buds. It is widely applied in Tea plantations and hedge-making.
(2)Root initiation- Auxins help to initiate rooting in stem cuttings. This application is widely used for plant propagation.
(3) Flowering: Auxins promote flowering in pineapple.
(4) Abscission: Auxins help to prevent fruit and leaf drop at early stages but promote the abscission of older mature leaves and fruits.
(5)Parthenocarpy: Auxin induces parthenocarpy in tomatoes.
(6)Herbicide/weedicide: Auxins used as herbicides. 2,4 D widely used to kill dicotyledonous weeds. 2.4 D does not affect mature monocotyledonous plants. It is used to prepare weed-free lawns by gardeners.
(7)Xylem differentiation : Auxin controls xylem differentiation.
(8)Cell division: Auxins helps in cell division
(9) Potato dormancy: MH (maleic hydrazide) and an NAA keep lateral buds of potato tubers dormant. Thus potato tubers can be stored for longer durations.

CYTOKININ:
(1)Cell division: Cytokinins have specific effects on cytokinesis (cytoplasmic division). It is considered as the most important biological effect of cytokinins.
(2) Overcome apical dominance: Cytokinins promote the growth of lateral buds. This role of cytokinin is an antagonist to auxin.
(3) Senescence: Cytokinins promote nutrient mobilisation towards vuong parts which helps in the delay of leaf senescence.
(4) Help to produce new leaves.
(5) Help to produce chloroplast in leaves.
(6) Promote lateral shoot growth.and adventitious shoot formation of leaves.
(7) Induce opening of stomata.
So from above the function of two enzymes, we come to know that CYTOKININ helps in mitosis and formation of shoots and lateral buds and AUXIN is helped in rooting.

Hence, the correct answer is option (C).

Note: The hormone which helps in shooting must be secreted in the high amount on the other hand the hormone which helps in rooting must have in less amount. Hence as per question for shooting cytokinin must have in its highest concentration.