Introduction:
Dicotyledonous plants are a group of flowering plants that possess two embryonic leaves known as cotyledons. These plants exhibit a variety of root systems, including taproot systems, which are characteristic of the majority of dicotyledon plants. The direct elongation of the radicle, the embryonic root, plays a crucial role in the formation of different types of roots in dicotyledon plants.

Formation of tertiary roots:
The direct elongation of the radicle in dicotyledon plants leads to the formation of tertiary roots. Tertiary roots are the small lateral roots that arise from the primary root or the taproot. They branch out from the primary root and spread in various directions, providing additional surface area for absorption of water and nutrients. Tertiary roots are responsible for anchoring the plant firmly in the soil and improving its overall stability.

Primary roots:
The primary root is the first root that emerges from the seed during germination. It grows vertically downwards and serves as the main root of the plant. In dicotyledon plants, the primary root usually undergoes elongation and thickening to develop into a taproot system.

Taproot system:
The direct elongation of the radicle in dicotyledon plants ultimately leads to the formation of a taproot system. The taproot is a large, central root that grows vertically into the soil. It acts as the primary anchoring structure and provides mechanical support to the plant. The taproot system also serves as a storage organ for nutrients, allowing the plant to survive in adverse conditions. From the taproot, secondary roots, also known as lateral roots, arise horizontally. These secondary roots further branch out into tertiary roots, forming a complex network that enhances water and nutrient absorption.

Secondary roots:
Secondary roots are lateral roots that arise from the primary root or taproot. They grow horizontally and help in the absorption of water and nutrients from a larger area of the soil. Secondary roots play a vital role in maintaining the plant's water balance and facilitating efficient nutrient uptake.

Conclusion:
In the majority of dicotyledon plants, the direct elongation of the radicle leads to the formation of tertiary roots, which branch out from the primary root or taproot. The primary root develops into a taproot system, consisting of a large central root and secondary roots that arise horizontally. The secondary roots further branch out into tertiary roots, forming a complex network that enhances water and nutrient absorption. This well-developed root system provides support, stability, and efficient nutrient uptake for dicotyledon plants.