The middle lamella is a thin layer of pectin and other polysaccharides that holds together adjacent plant cells. It is composed of a variety of elements, but the most abundant element present in the middle lamella is calcium (Ca).

Explanation:

Composition of middle lamella:

- The middle lamella is composed of a variety of polysaccharides, including pectin, hemicellulose, and cellulose.
- It also contains various proteins and enzymes, as well as minerals such as calcium (Ca) and magnesium (Mg).

Role of calcium in middle lamella:

- Calcium plays a crucial role in the formation and maintenance of the middle lamella.
- It acts as a cementing agent, binding adjacent plant cells together.
- Calcium ions are positively charged and can form cross-links with negatively charged pectin molecules in the middle lamella, strengthening the cell wall and providing structural support to the plant.

Other elements present in middle lamella:

- Apart from calcium, other elements such as potassium (K), magnesium (Mg), and sodium (Na) are also present in the middle lamella, but in much smaller quantities.
- These elements play important roles in various cellular processes, such as ion transport, enzyme activation, and osmoregulation.

Conclusion:

Thus, the correct answer is option 'C' (Ca), as calcium is the most abundant element present in the middle lamella and plays a crucial role in maintaining the structural integrity of plant cells.