Question

Tertiary roots are
A. Positively geotropic
B. Negatively geotropic
C. Plagiogeotropic
D. Ageotropic

Answer 1

Hint: The primary root develops horizontally into the soil. On the primary root, smaller lateral roots known as the secondary roots are formed. Tertiary roots are formed by secondary roots in turn. Such roots grow in different directions and help to fix the plant securely in the soil.

Complete answer: The tertiary root system consists of two or more genetically and functionally different root groups, smaller than 0.6 mm in diameter, which affect the functionality found in developed root systems. The lateral roots are none other than roots that grow horizontally from the radical primary root and help to properly anchor the plant in the soil. This branching is essential for the absorption of water, promoting the uptake of nutrients. The secondary and tertiary roots comprise lateral roots. Tertiary roots are considered the branches of the secondary roots. There is little or no geotropic sensitivity in some of the lateral organs. It is, therefore, referred to as being ageotropic. An example of such a plant: the Cycas of the coralloid root. The taproot is the primary root that grows from the embryo's radicle elongation and remains throughout the plant's existence. This produces lateral or secondary roots that further break to form tertiary roots.
Hence, the correct answer is option D.

Note: The primary root that persists as the main root throughout the life of a plant and grows straight downwards in the soil is the taproot. Other branches originate from the taproot, such as secondary roots, tertiary roots, rootlets, etc are examples of the taproot system. Most generally, the taproot system is present in dicots. Mangifera, Azadirachta, Gossypium, for instance, etc.