Q.Collenchyma is a type of ................. tissue.

Simple permanent tissue is built from a single type of cell performing a single kind of function, and includes three named tissues that between them cover the full range from purely living-and-flexible to purely dead-and-rigid. Parenchyma is thin-walled, living, cellulosic, and only lightly specialised — its cells are isodiametric to elongated with a prominent nucleus and a large vacuole, and small intercellular spaces are typical; besides basic storage, parenchyma is the tissue most capable of dedifferentiating back into a meristem (for instance, into vascular or cork cambium during secondary growth). Collenchyma is also living, but its cellulose-and-pectin wall is thickened unevenly, concentrated at the corners where cells meet, and its cells are packed with no intercellular gaps; because this uneven thickening is flexible rather than rigid, collenchyma functions as a living mechanical tissue that lets young stems and petioles bend and stretch without tearing — it is notably absent from monocot stems and dicot roots. Sclerenchyma, finally, is dead at maturity: its walls are uniformly thickened with lignin, and it occurs as two forms — narrow, tapering, bundle-forming fibres that provide tensile strength (and are the source of commercial plant fibres like jute and hemp), and broad, blunt-ended sclereids, arising from thickened parenchyma, that provide stiffness rather than tensile strength.