Question

Differentiation of shoot is controlled by ___________

• A. high gibberellin to auxin ratio
• B. high auxin to cytokinin ratio
• C. high gibberellin to cytokinin ratio
• D. high cytokinin to auxin ratio
  

Answer 1

The correct option is D high cytokinin to auxin ratio


One of the major functions of cytokinin is it helps in cell division. Skoog and Miller experimented on the effect of auxin and cytokinin on the growth and differentiation of tissues in culture.

In tissue culture, when a plant part is added to a nutrient medium they dedifferentiate to form a mass of cells called callus which possess meristematic activity.
They can either remain undifferentiated or can differentiate to form roots and shoots. It was observed that cytokinin induces shoot formation while auxin induces in root formation.

It was later experimentally proved that generally:
i. High cytokinin to auxin ratio leads to the differentiation of shoot
ii. Low cytokinin to auxin ratio leads to the differentiation of root
iii. Intermediate cytokinin to auxin ratio leads to the differentiation of both root and shoot
iv. Intermediate cytokinin to low auxin ratio leads to callus formation.