Question

In tissue culture, roots can be induced by
a. Lower concentration of cytokinin and higher concentration of auxins
b. Only cytokinin and no auxins
c. No cytokinin and only auxins.
d. Higher concentration of cytokinin and lower concentration of auxins

Answer 1

Hint: Auxins promote the cell division and root differentiation. Cytokinin in higher concentration promotes shoot production. Both these hormones cross link with each other. Cytokinin promotes the cell to switch from the meristematic to differentiated state through inhibiting auxin signaling.

Complete answer:
Plant growth regulators are very important for the growth of the plants. There are mainly five types of plant growth hormones such as auxins, cytokinin, gibberellins, ethylene and abscisic acid.

Tissue culture is the artificial method of growing plants in a lab from the tissues of the plants. They require nutrient medium for this. The nutrient or culture medium contains all the required materials for plant growth such as plant hormones and the nitrogen source. It affects the morphology of the tissues that grow from the initial explants.

Auxins are present at the tips of the plant parts such as young shoot organs, promotes root development and induces vascular differentiation while the cytokinin synthesized in root cap, promotes cytokinesis and vascular cambium.

When the auxin is present in excess amount it results in a proliferation of roots, excess of cytokinin promotes shoot development. A balance of both auxin and cytokine can help in the production of callus. The development of the outgrowth depends on the morphology of the plant species and medium composition. Cytokinin can inhibit the auxin signaling and reduce root proliferation.

From the above information we can say that Lower concentration of cytokinin and higher concentration of auxins can induce roots in tissue culture.

Hence, the correct answer is option (A).

Note: The type of interaction between auxin and cytokinin that governs developmental outputs in plants is known as Antagonism. Another type of interaction between these hormones helps in nodule organogenesis, light mediated leaf initiation and organ positioning. Cytokinin also induces embryogenesis and maintenance of roots and shoots meristem.