collenchyma

Collenchyma is a type of simple plant tissue that provides mechanical support to growing parts of the plant. It is composed of elongated living cells with unevenly thickened primary cell walls, typically thickened at the corners. The thickening is due to cellulose and pectic substances, and the walls are not lignified, allowing flexibility as the organ grows. Collenchyma cells remain alive at maturity and often contain substantial cytoplasm.

Collenchyma is derived from the ground meristem during primary growth and is commonly found in the stems, petioles, and leaf stalks of herbaceous dicots. It usually lies beneath the epidermis and around vascular bundles, forming continuous cylinders or strands that elongate with the organ. The tissue is particularly important in regions undergoing rapid elongation, where rigid support would hinder growth.

Types of collenchyma are distinguished by the pattern of wall thickening. Angular collenchyma shows thickening at the corners of cells; lamellar collenchyma thickens along the walls in parallel layers; lacunar collenchyma features intercellular spaces or lacunae. These variants contribute to differing mechanical properties and space arrangement within tissues.

Functionally, collenchyma provides flexible, elastic support that helps maintain organ integrity while accommodating growth. It contrasts with sclerenchyma, whose cells are lignified and typically dead at maturity, and with parenchyma, which is usually storey and less structurally specialized.