in submerged hydrophytes,the stems are extremely weak due to

Options

A. absence of phloem
B. absence of xylem
C. presence of aerenchyma
D. poor development of xylem and mechanical tissue.

Answer

**Step-by-Step Solution:**

1. **Understanding Hydrophytes**: Begin by recognizing that hydrophytes are plants that grow in water. They have adapted to their aquatic environment, which influences their structure and function.

2. **Analyzing the Options**: The question provides several options regarding why the stems of submerged hydrophytes are weak. We need to evaluate each option carefully.

3. **Evaluating Absence of Phloem**: The first option states that the stems are weak due to the absence of phloem. This is incorrect because phloem is essential for transporting food throughout the plant. Without it, the plant would not survive.

4. **Evaluating Absence of Xylem**: The second option mentions the absence of xylem. This is also incorrect, as xylem is crucial for water transport. A lack of xylem would lead to the plant's death due to insufficient water supply.

5. **Evaluating Presence of Aerenchyma**: The third option refers to the presence of aerenchyma. Aerenchyma are specialized parenchyma cells that contain air spaces, providing buoyancy to the plant. This option is incorrect because aerenchyma actually help support the plant in water, rather than weaken it.

6. **Evaluating Poor Development of Xylem and Mechanical Tissue**: The fourth option states that the stems are weak due to the poor development of xylem and mechanical tissues. This is the correct answer. In submerged hydrophytes, the pressure and stress experienced by the plant are minimal, leading to reduced development of these supportive tissues.

7. **Conclusion**: Based on the analysis, the stems of submerged hydrophytes are extremely weak due to the poor development of xylem and mechanical tissues.

**Final Answer**: The stems are extremely weak due to the poor development of xylem and mechanical tissues.

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