The plastid is a major double-membrane organelle found in the meristematic tissues especially inside parenchyma cells of the plants or leaves, and the Parenchyma is present inside the central leaf or mesophyll

Mesophyll
The tissue in a leaf where plastids are present is called the mesophyll. Mesophyll is the inner tissue of a leaf, located between the upper and lower epidermis. It is the main photosynthetic tissue of the leaf and contains chloroplasts, which are a type of plastid responsible for carrying out photosynthesis.

Plastids in Mesophyll
Plastids are specialized organelles found in plant cells, including chloroplasts, chromoplasts, and leucoplasts. Chloroplasts are the most common type of plastid in mesophyll cells and are responsible for the green color of leaves due to the presence of chlorophyll. These chloroplasts play a crucial role in converting light energy into chemical energy during photosynthesis.

Function of Plastids in Mesophyll
Plastids, particularly chloroplasts, are essential for the process of photosynthesis, where they capture light energy and convert it into glucose, a form of energy that plants can use. This process involves the absorption of light by chlorophyll, the conversion of carbon dioxide and water into glucose, and the release of oxygen as a byproduct.

Importance of Mesophyll Tissue
Mesophyll tissue is critical for the overall functioning of a leaf as it houses the majority of chloroplasts responsible for photosynthesis. This tissue is well adapted for efficient gas exchange and light absorption, making it crucial for the plant's survival and growth. The presence of plastids in the mesophyll allows plants to produce their own food and sustain themselves through the process of photosynthesis.