Question

Commercial cork is obtained from
A)Berberis/Barberry
B)Salix/Willow
C)Quercus/Oak
D)Betula/Birch

Answer 1

Hint: Due to its lightweight, high compressibility, durability, moisture resistance, low thermal conductivity, vibration absorption power, etc.cork is economically significant.

Complete answer:
Commercial cork is derived from the periderm layers of a Quercus suber plant (cork oak tree). The plant typically exhibits extra stelar secondary growth and shapes the cork layers. But when the plant is around 20 years old, these virgin cork layers are removed by stripping. Tissues that are exposed dry out. Under the dry layers, the plant now establishes a phellogen layer and rapidly produces large amounts of higher quality cork cells.

This new cork layer attains ample thickness for commercial use after 9 to 10 years and is removed. The consistency of this cork is higher than virgin cork. Some stripping takes place until the plant is 150 years old. The cork quality after the second stripping, however is bad.

After the original rough outer bark is removed, cork is collected from the new outer sheath of bark produced by the inner bark. Then the outer sheath will be stripped and will form again. The outer bark, or cork, is not essential to the survival of the tree, unlike the inner bark, and acts merely to shield it from the Mediterranean summer heat and dry winds.

Repeated stripping of cork is possible since a particularly uniform and continuous regenerative tissue grows in the inner bark of the cork oak. This tissue proliferates ample cork cells to the outside after the outer bark has been peeled, so that in a healthy tree, 2.5-5 cm (1-2 inches) of uniform new cork sheathing develops in 3 to 10 years. Stripping this regenerated layer yields slabs of industrial cork.

Hence, the correct answer is option (C)

Note: The cork is processed to various thicknesses and sizes. The presence of air in its cells accounts for much of the cork's characteristics. Cork is used to make bobbins, rollers, materials for soundproofing, chambers for cooling, caps, insulators, shock absorbers, etc.