Question

23. Find the correct application of cytokinin.
[NCERT Pg. 248-250]
(1) Acts as antitranspirant and induces closure of
stomata
(2) To promote root development on various types
of cuttings
139 In tea plantation for giving bushy appearance
(4) Promotes parthenocarpy in fruits like banana
and grapes​

Answer 1

Answer:

It promotes bud in the plant

Answer 2

Answer:

(1) Acts as antitranspirant and induces closure of stomata

Explanation:

• While ABA is the antitranspirant which promotes stomatal closure under water stress, cytokinin is the antagonist to ABA promoting stomatal opening.

• The opening and closing of stomata are regulated by the increases or decreases of solutes in the guard cells. The stomata open and close because of water and ion movements.

• During photosynthesis, the potassium ($K^{+}$) ions transfer into the guard cells and form a gradient. For this absorption of potassium ions, it needs protons ($H^{+}$) to balance and replace it.

• The absorption of potassium ions refers to influx into the guard cells and the forward movement of protons is called efflux.

• This active ionic change needs ATP and cytokinin which help potassium ions to move in the guard cells, resulting in low proton concentrations in the same. As a result guard cells swell up and stomata open.

• Cytokinin is the major phytohormone involved in plant growth and development. This phytohormone is known to antagonize the effects of abscisic acid on stomatal movement. Hence cytokinin is anti to the effects of antitranspirant.

Therefore the correct application of cytokinin is option 1).