Question

Which of the following effects of auxins on the plants is the basis for commercial application?
A. Callus formation
B. Curvature of stem
C. Induction of root formation in stem cuttings
D. All of the above

Answer 1

Hint:-Auxins are a class of plant hormones with some morphogen-like features (or plant-growth regulators). In the coordination of many growth and behavioural processes in plant life cycles, auxins play a cardinal role and are essential for the development of the plant body.

Complete Answer:-Auxins promote elongation of the stem, inhibit lateral bud growth (maintains apical dominance). The stem, buds, and root tips are produced in them. Ex: Indole Acetic Acid (IAA). Auxin is a plant hormone produced at the tip of the stem that promotes elongation of cells. Auxin travels to the darker side of the plant, allowing the cells on the lighter side of the plant to grow bigger than the equivalent cells there. This produces a curve toward the light of the plant stem tip, a plant motion known as phototropism.

In the maintenance of apical dominance, Auxin also plays a role. Most plants are located at nodes (where leaves attach to the stem) with lateral (sometimes called axillary) buds. Buds are embryonic meristems in a dormant state that are retained. This dormancy is preserved by Auxin. The lateral buds remain dormant as long as the apical meristem generates enough auxin. The auxin is no longer produced if the apex of the shoot is removed.

From these discussions we can conclude that auxins will promote Callus formation, Curvature of stem and Induction of root formation in stem cuttings.

Therefore the correct answer is option (D).

Note:- In plant nurseries and for crop production, the commercial use of auxin is widespread. IAA is used to encourage the growth of adventitious roots on cuttings and detached leaves as a rooting hormone. The application of synthetic auxins in greenhouses to tomato plants promotes normal fruit development. Auxin's outdoor application promotes fruit setting and dropping synchronisation, which coordinates the harvesting season. By treating unfertilized plants, fruits such as seedless cucumbers can be induced to produce fruit.