What are parenchyma, collenchyma and sclerenchyma?
Parenchyma, collenchyma and sclerenchyma are three types of simple permanent tissues, collectively called ground tissue in plants.
This tissue is present in all organs of the plants e.g. roots, stems, leaves, flowers, fruits, and seeds. It is a versatile ground tissue that generally constitutes the filler tissue in soft parts of the plants. It forms the cortex and pith of stems, cortex of roots, mesophyll of leaves, the pulp of fruits and the endosperm of seeds. Tissues that specialise in food storage are commonly formed of parenchyma.
It is generally found as 3 - 4 layered hypodermis of herbaceous dicotyledonous stem. They are absent in monocot stems. They are mostly found adjacent to outer growing tissues such as vascular cambium. Collenchyma provides structural support, particularly in growing shoots and leaves. For example they make up the resilient strands of celery.
They are usually associated with the xylem and phloem of the vascular bundles. Sclerenchyma fibres are of great economic importance and are present in hypodermis of monocot stems, in pericycle of many dicots, in secondary wood, in vascular bundle sheath in monocot stems and hypodermis of many leaves.
Bundles of sclerenchyma (sclerids) form durable layers such as the shell of nuts and seeds as well as stones of drupes. They also constitute the core of apples and the gritty structure of pears.