Apical Dominance in higher plants is due to Phytohormones. Phytohormones are naturally occurring organic substances that regulate plant growth and development. They are also known as plant hormones or growth regulators. Phytohormones are synthesized in one part of the plant and transported to other parts where they exert their effects.

Explanation:

1. Definition of Apical Dominance:

Apical dominance is the phenomenon in which the apical bud of a plant inhibits the growth of lateral buds below it. This ensures that the plant grows in a single, upward direction, with a dominant main stem.

2. Role of Phytohormones:

Phytohormones play a crucial role in apical dominance. The apical bud releases a hormone called auxin, which inhibits the growth of lateral buds. Auxin is produced in the apical meristem (the growing tip of the plant) and is transported downwards towards the base of the plant.

3. Mechanism of Phytohormones:

Auxin acts by inhibiting the growth of lateral buds by inducing the production of cytokinins in the roots. Cytokinins are another type of phytohormone that promote cell division and growth. When auxin is transported downwards towards the roots, it induces the production of cytokinins in the roots. These cytokinins are then transported upwards towards the lateral buds, where they promote cell division and growth. However, the concentration of cytokinins is not enough to overcome the inhibitory effect of auxin, so the lateral buds remain dormant.

4. Importance of Apical Dominance:

Apical dominance is an important mechanism for plants because it ensures that the plant grows in a single, upward direction, with a dominant main stem. This is important for plants that need to compete for light and space. By growing upwards, the plant can maximize its exposure to sunlight and outcompete other plants for resources.

Conclusion:

In conclusion, Apical Dominance in higher plants is due to Phytohormones. Auxin is the hormone responsible for inhibiting the growth of lateral buds, while cytokinins promote cell division and growth. The balance between these two hormones ensures that the plant grows in a single, upward direction, with a dominant main stem.