Question

The Grittiness in the pulp of pears and guava is due to .............. of sclerenchyma tissue.

Answer 1

Hint: Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified cellular walls that form small bundles of durable layers of tissue in most plants.


Complete answer:
1. The presence of numerous sclereids form the cores of apples and produce the gritty texture of guavas and pears. Sclerenchyma, in plants, support tissue composed of any of various kinds of hard woody cells.
2. Mature sclerenchyma cells are usually dead cells that have heavily thickened secondary walls containing lignin. The cells are rigid and non stretchable and are usually found in nongrowing regions of plant bodies, such as the bark or mature stems.
3. Sclerenchyma is one of the three types of ground, or fundamental, tissue in plants; the other two types are parenchyma (living thin-walled tissue) and collenchyma (living support tissue with irregular walls).
4. Sclerenchyma cells occur in many different shapes and sizes, but two main types occur: fibres and sclereids. Fibres are greatly elongated cells whose long, tapering ends interlock, thus providing maximum support to a plant.
5. They often occur in bundles or strands and can be found almost anywhere in the plant body, including the stem, the roots, and the vascular bundles in leaves. Many of these fibres, including seed hairs, leaf fibres, and bast fibres, are important sources of raw material for textiles and other woven goods.
6. Sclereids are extremely variable in shape and are present in various tissues of the plant, such as the periderm, cortex, pith, xylem, and phloem. They also occur in leaves and fruits and constitute the hard shell of nuts and the outer hard coat of many seeds.
7. Sometimes known as stone cells, sclereids are also responsible for the gritty texture of pears and guavas. Although sclereids are variable in shape, the cells are generally isodiametric, prosenchymatic, forked, or elaborately branched.
8. They can be grouped into bundles, can form complete tubes located at the periphery, or can occur as single cells or small groups of cells within parenchyma tissues. An isolated sclereid cell is known as an idioblast.
9. Sclereids are typically found in the epidermis, ground tissue, and vascular tissue. The presence of numerous sclereids form the cores of apples and produce the gritty texture of guavas.
10. Lumpy, bumpy pears might indicate scab disease, or may be a result of fluctuating soil moisture during fruit formation. Scab is a fungal disease that can be prevented with regular applications of lime-sulfur.
11. We get a crunchy and granular feeling when we chew pear fruit because of the presence of sclerenchyma tissue. The sclerenchyma cells are of two types- fibres and sclereids. The sclereids give a crunchy feeling to the pear fruit because it provides support and hardens the tissue.
12. Fibre bundles are often several feet long and composed of overlapping cellulose fibres and a cohesive gum, or pectin, which strengthens plant stems. The fibres are located between the epidermis, or bark surface, and an inner woody core.
13. In harvesting bast fibres, the plant stalks are cut off close to the base or pulled up. The fibres are usually freed from the stalk by retting but are sometimes obtained by decortication, a manual or mechanical peeling operation.

Note: The tissue is found chiefly in the cortex of stems and in leaves and is the primary supporting tissue for many herbaceous plants. In plants with secondary growth, the collenchyma tissue is only temporarily functional and becomes crushed as woody tissue develops. It often constitutes the ridges and angles of stems and commonly borders the veins in eudicot leaves.