Question

Removal of apical bud results in
A. Formation of new apical bud
B. Elongation of the main stem
C. Death of plant
D. Formation of lateral branching

Answer 1

Hint: Plant growth regulator auxin is present at the shoot apices and it causes apical dominance in plants. On removal of apical bud apical dominance is no longer observed and this technique is used in hedge making.

Complete answer:
The apical bud when present does not allow the growth of axillary or vegetative buds. This phenomenon is known as apical dominance, the apical bud causes suppression of the axillary buds and therefore only the main stem gets elongated. When the apical bud is removed by decapitation, apical dominance is also removed, and therefore lateral buds show growth resulting in the formation of lateral branches. The hormone responsible for apical dominance is an auxin named IAA or indole-3-acetic acid.

Additional Information:
> This technique where apical bud is removed resulting in the removal of apical dominance is widely used in tea plantations.
> The hormone auxin is a plant growth regulator and it exhibits several other physiological effects on plants as mentioned below:
- Cell elongation and cell division: Auxin promotes elongation and division of cells. It helps is solubilization and distribution of carbohydrates, and increases flexibility of cell wall microfibrils and thus helps in cell elongation. Stimulates cell division and therefore it is used in tissue culture technique.
- Auxin also promotes xylem differentiation.
- Weed removal: Auxins act as weedicides and help in eradication of unwanted weeds from the agricultural fields. 2,4-D and 2,4,5-T are commonly used weedicides which are chemically auxins.
- Parthenocarpy: Helps in the formation of seedless fruits.
- Fruit Sweetener: Auxins like maleic hydrazide and Indole-3-butyric acid help in the sweetening of fruits.

So, the correct answer is, “ Removal of apical bud results in the formation of lateral branching.”

Note: Bioassay is a technique used for testing biological processes like growth, maturation promoted in a living sample by the use of a chemical compound. It is used to understand how a particular chemical substance may affect some physiological processes in a certain living sample. Two types of bioassay are done for auxin, Avena curvature test, and cress root inhibition test. Cell to cell movement of auxins can happen by both passive and active discussion.