Roots and shoots lengthen through activity at :

Options

A. apical meristems
B. vascular cambium
C. lateral meristems
D. cork cambium

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where the lengthening of roots and shoots occurs in plants. This refers to the growth process that increases the length of these structures.

2. **Identifying Key Terms**: The terms "roots," "shoots," "lengthen," and "activity" are crucial. In biological terms, the growth at the tips of roots and shoots is significant.

3. **Recognizing the Role of Meristematic Tissue**: The primary tissue responsible for the lengthening of roots and shoots is called meristematic tissue. There are two main types of meristematic tissue involved in this process:
- **Apical Meristematic Tissue**: This is located at the tips (apices) of roots and shoots. It is responsible for primary growth, which increases the length of the plant.
- **Intercalary Meristematic Tissue**: Found at the base of nodes and internodes, this tissue also contributes to the lengthening of the plant.

4. **Mechanism of Growth**: Apical meristematic cells divide continuously through mitosis. This division results in the formation of new cells, which leads to an increase in the number of cells at the tips of roots and shoots, thereby lengthening them.

5. **Conclusion**: The lengthening of roots and shoots occurs due to the activity of apical meristematic tissue at the tips of these structures. This growth is referred to as primary growth.

**Final Answer**: Roots and shoots lengthen through activity at the apical meristematic tissue located at their tips.

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