The narrow cavity or lumen is found in Sclerenchyma tissue.

Sclerenchyma tissue is one of the three types of ground tissue in plants, along with parenchyma and collenchyma. It is characterized by thickened, lignified cell walls that provide strength and support to the plant. Sclerenchyma cells are dead at maturity and lack protoplasts, making their cell walls rigid and durable.

Sclerenchyma tissue can be further classified into two types:
1. Fibers: These are elongated cells with tapering ends. They are found in clusters or bundles and provide mechanical support to the plant.
2. Sclereids: These are shorter, irregularly shaped cells that occur singly or in groups. They are found in various plant parts and impart hardness and strength.

Explanation:
The narrow cavity or lumen referred to in the question is characteristic of sclerenchyma tissue. The term "cavity" or "lumen" refers to the space or void within a cell or tissue. In the case of sclerenchyma, the lumen is narrow due to the thickened cell walls. The cell walls of sclerenchyma cells are heavily lignified, meaning they contain a high amount of lignin, a complex polymer that provides rigidity and strength. The deposition of lignin in the cell walls reduces the size of the lumen, resulting in a narrow cavity.

The narrow lumen in sclerenchyma cells serves an important function. It enhances the mechanical strength and support provided by these cells. The thickened cell walls, along with the narrow lumen, allow sclerenchyma cells to withstand mechanical stress and provide structural support to the plant. They are commonly found in regions of the plant that require rigidity, such as the stems, vascular tissues, and seed coats.

In contrast, parenchyma and collenchyma tissues have larger lumens compared to sclerenchyma. Parenchyma cells are unspecialized and have thin cell walls, while collenchyma cells have unevenly thickened cell walls. These tissues are involved in various functions such as storage, photosynthesis, and tissue repair, but they do not provide the same level of mechanical support as sclerenchyma.

Conclusion:
In conclusion, the narrow cavity or lumen is a characteristic feature of sclerenchyma tissue. The thickened, lignified cell walls in sclerenchyma cells result in a reduced lumen size, enhancing their mechanical strength and support function in plants.

Scelerenchyma