Parenchyma

Abstract In plants, parenchyma refers to a tissue composed of living cells, usually having only thin, primary cell walls and varying widely by morphology and metabolism. Parenchyma in the primary plant body often occurs as a continuous mass, such as in the cortex or pith of stems and roots, the mesophyll of leaves and the flesh of fruits. In vascular tissue parenchyma cells form axial strands that run along the length of the plant body and, where secondary growth occurs, in radial files that run from the outer tissues towards the pith. The unifying characteristic of all parenchyma cells is that they are living at maturity and capable of cell division, giving them important roles in regeneration and wound healing. Other key functions of these cells include photosynthesis, storage, secretion and transport. Key Concepts: Parenchyma refers to both a cell type and a simple tissue and is found within all three tissue systems of vascular plants: the dermal, ground (fundamental) and vascular tissue systems. Parenchyma functions are diverse and dependant on both location within the plant and morphological specialisation. Parenchyma forms the bulk of plant ground tissue, where they may be specialised to function in photosynthesis, storage, or transport. Parenchyma is integral to vascular tissue, where it provides a route of exchange for materials within and between the xylem and the phloem. Parenchyma is composed of living cells that retain the ability to divide and hence play a key role in several developmental processes, as well in plant response to wounding.