Question

Why does cells of sclerenchyma tissue have a narrow layer of lumen?(please give an explanation).

Answer 1

The lumen is the vacuole of the sclerenchyma cells. They form a bulk of mechanical tissues 

Answer 2

every cell is having vacuole, as sclrenchyma cells are dead, the vacuole of the cell is represented by an empty sapce called lumen, which runs through out the length of the cell.