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30

The cross-section of a plant material showed the following features when viewed under the microscope.

(a) The vascular bundles were radially arranged.

(b) Four xylem strands with exarch condition of protoxylem. To which organ should it be assigned?

Explanation
Root is the organ which shows the features given in the question. Vascular bundles are present on separate radii thus called radial arrangement. Protoxylem is towards periphery of root thus making exarch condition.
31
What do hardwood and softwood stand for?
Explanation

Distinguish between softwood and hardwood is as

Softwood Hardwood
Gymnospermic wood is soft wood
It chiefly contains trachieds
Vessels are absent.
Angiospermic wood is hard wood It chiefly contain both trachieds and vessels Trachieds are absent.

32
While eating peach or pear it is usually seen that some stone like structures get entangled in the teeth, what are these stone like structures called?
Explanation

The pulpy part of fruit of peach and pear, the stone cells are present, which are an sclerenchymatous cells and which are dead in nature. Their function is to give mechanical support to the soft tissue.

33
What is the commercial source of cork? How is it formed in the plant?
Explanation
The commerical cork is obtained from the cork tissue of Quercus suber, which yields bottle cork. Cork is formed by cork cambium or phellogen cell. Cork cambium cells divide periclinally, cutting cells towards the inside and outside. The cells cut off twowards the outside become suberised and dead. These are compactly packed in radial rows without intercellullar spaces and form cork of phellem. Cork is impervious to water due to suberin and provides protection to the underlying tissues.
34

Below is a list of plant fibres. From which part of the plant these are obtained

(a) coir (b) hemp (c) cotton (d) jute

Explanation

(a) Coir It is a natural fibre obtained from husk of coconut. It is the fibrous mesoderm of the coconut fruit Cocos nucifera.

(b) Hemp The fibre is obtained from the stems of Cannabis sativa. It is the bast fibre (soft or stem fibre) obtained from secondary phloem.

(c) Cotton The fibre is the epidermal growth of cotton (Gossypium hirsutum) seed. It is elongated structure made up of cellulose.

(d) Jute It is a natural bast fibre obtained from Corchorus capsularis and made up of cellulose and lignin.