Question

In plant tissue culture experiments, high auxin to cytokinin ratio favours …………… development and high cytokinin to auxin ratio favours ……………development.
A. Root, shoot
B. Shoot, root
C. Root, root
D. Shoot, shoot

Answer 1

Hint: Auxins and cytokinins are phytohormones or plant hormones. They are also called plant regulators as they regulate growth and development in plants. Plant hormones are chemical compounds found in plant parts in very low concentration. Besides auxin and cytokinins, gibberellins, abscisic acid and ethylene are other naturally occurring plant hormones. The development of the root, stem, leaf and flower, shedding of leaves and the development and ripening of fruits are some of the roles of plant homes.

Complete answer:
Both auxin and cytokinin work either synergistically (together) or antagonistically (opposite) in controlling several significant physiological processes in plants. The ratio of auxin to cytokinin plays an important role in plant growth. When tissue is cultured with auxin but no cytokinin, they grow into a callus. A callus is an unorganized, undifferentiated mass of cells. But no division in the callus cells. When cytokinin is added, cell division occurs and callus differentiates. If the concentration of cytokinins is more than auxin, it favours the development of shoot buds. If the concentration of auxin is more than cytokinins, it favours the development of roots. Therefore, shoot development is promoted by more cytokinin such as BAP (Benzylaminopurine) than auxin such as NAA (Naphthalene acetic acid). Whereas, root development is promoted by more auxin than cytokinin.

Thus, option A Root, the shoot is the correct answer.

Note:
The shoot and root development in culture is controlled by auxin-cytokinin balance. More auxins promote root development and more cytokinins promote shoot development.