I. Helps in the formation of middle
II. Needed in spindle fibre formation
III. Accumulates in older leaves
IV. Involved in normal functioning of cell membrane
V. Activates certain enzymes like succinate dehydrogenase.
The above list is associated with -

Options

A. Fe
B. Mg
C. Ca
D. Cu

Answer

To solve the question regarding the association of the given points with a specific element, we can analyze each statement step by step:

### Step-by-Step Solution:

1. **Formation of Middle Lamella**:
- The middle lamella is a layer that cements adjacent plant cells together. It is primarily composed of pectins and requires calcium for its formation. Calcium ions help in stabilizing the structure of the middle lamella.

**Hint**: Think about which mineral is known for its structural role in plant cell walls.

2. **Spindle Fiber Formation**:
- During cell division, spindle fibers are crucial for the separation of chromosomes. Calcium plays a role in the formation and function of these fibers, facilitating the process of mitosis.

**Hint**: Consider the importance of calcium in cellular processes, especially during division.

3. **Accumulation in Older Leaves**:
- Calcium is considered an immobile element in plants, meaning it does not move from older tissues to younger ones when there is a deficiency. As a result, it tends to accumulate in older leaves.

**Hint**: Reflect on the mobility of nutrients in plants and how that affects their distribution.

4. **Normal Functioning of Cell Membrane**:
- Calcium is essential for maintaining the integrity and function of cell membranes. It helps in stabilizing the membrane structure and is involved in signaling pathways.

**Hint**: Think about how calcium ions interact with cell membranes and their role in cellular signaling.

5. **Activation of Enzymes like Succinate Dehydrogenase**:
- Calcium ions are known to activate various enzymes, including succinate dehydrogenase, which is involved in the Krebs cycle and energy production in cells.

**Hint**: Consider the role of calcium in metabolic pathways and enzyme activation.

### Conclusion:
Based on the analysis of the points provided, all the statements are associated with **Calcium**. Therefore, the correct answer to the question is **Calcium**.