Sclerenchyma tissues are the strengthening tissues found in plants having dead cells. Their walls are thick because they have lignin deposited in their walls.
Parenchyma are living tissues found in all organs of a plant, concerned with storage of food. Collenchyma tissues are living tissues that are thickened at angles. They provide mechanical support to plant and epithelial tissues are living cells found as the outermost layer of an organ that function in secretion, protection, absorption, sensing etc.