Question

Secondary growth is absent in
A. Hydrophytes
B. Mesophytes
C. Halophytes
D. Xerophytes

Answer 1

Plants have two different types of meristems. First one is Apical Meristems that causes the increase of a plant and the second one is Lateral Meristems that causes the Lateral growth of a plant. Lateral meristems are responsible for thickening the stems as well as roots. Lateral meristems are also called Vascular Cambiums.

Complete explanation
Option A. Hydrophytes: The plants which can grow partially or fully submerged in water are called Hydrophytes. They don’t show secondary growth due to the absence of vascular cambium or lateral meristems.
So, Option A. Hydrophytes is the correct answer.
Option B. Mesophytes : Mesophytes are those plants that Can live in an average supply of water. They have Vascular cambium or lateral meristems, so that we can see secondary growth in them.
So, Option B. Mesophytes is not the correct answer.
Option C. Halophytes: Halophytes are the salt-tolerant plants that grow in areas like mangroves and sea shores. They also have Vascular cambium or lateral meristems. So they also have secondary growth.
So, Option C. Halophytes is not the correct answer.
Option D. Xerophytes: Xerophytes are the dessert tolerant plants. Naturally their stems and leaves become fleshy and store water inside. This is an example of Secondary growth and they have vascular cambium that helps them in secondary growth.
So, Option D. Xerophytes is not the correct answer.

So, Option A. Hydrophytes is the correct answer.

Note:
Apical meristems are found at the tips of shoots and roots of a vascular plant. This meristem causes the plant to grow tall. On the other hand the lateral meristems are found in the stems and roots. This meristem makes stems and roots get thicker sidewise.