NCERT Class 11-Biology: Chapter –6 Anatomy of Flowering Plants Part 4

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Question 10:

Arrange the following in the sequence you would find them in a plant starting from the periphery – phellem, phellogen, and phelloderm.

Answer:

Phellem or cork is the outer most layers, followed by phellogen (cork cambium) which in turn is followed by phelloderm (secondary cortex).

Hence the sequence is as follows:

Phellem → Phellogen → Phelloderm

Question 11:

If one debarks a tree, what parts of the plant is being removed?

Answer:

If one debarks a tree then periderm part (i.e., all tissues exterior to vascular cambium) of the plant is being removed.

Periderm contains phellogen, phellem and phelloderm.

Bark also contains secondary phloem.

Question 12:

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?

Answer:

The cross-section is of dicot root.

Vascular bundles are present are arranged in alternate manner on separate radii thus called radial arrangement.

Protoxylem is towards periphery of root thus making exarch condition.

Question 13:

What do hard wood and soft wood stand for?

Answer:

Hard wood are wood from angiosperm, whereas soft wood are wood from gymnosperm.

Soft wood are soft due to absence of vessels also known as non-porous wood. It mainly contains tracheid’s.

Hard wood contains abundant of vessels. In this no tracheid’s is present.

Short Answer Type Questions

Question 1:

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?

Answer:

The stone like structures present in peach or pear are stone cells also known as Sclereids.

Sclereids are type of Sclerenchyma which provides mechanical support to organs.

The Sclereids are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities (lumen).

Question 2:

What is the commercial source of cork? How is it formed in the plant?

Answer:

The commercial source of cork is cork tissue of Quercus suber.

Due to the activity of vascular cambium the stem increases in girth. So the outer cortical and epidermis layers get broken and need to be replaced by new protective cell layers. Hence another meristematic tissue called cork cambium or phellogen develops in the cortex region.

Phellogen is a couple of layers thick. It is made of narrow, thin-walled and nearly rectangular cells. Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem while the inner cells differentiate into secondary cortex or phelloderm.

The cork is impervious to water due to suberin deposition in the cell wall and provides protection to the underlying tissues.

Question 3:

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

a. Coir

b. Hemp

c. Cotton

d. Jute

Answer:

a. Coir is natural fibre obtained from coconut husk. Coir is mesocarp of coconut. It is the fibrous mesoderm of the coconut fruit Cocosnucifera.

b. Hemp fibre is obtained from the stem of cannabis sativa. It is the best fibre (soft or stem fibre) obtained from secondary phloem.

c. Cotton fibre is obtained from epidermal growth of cotton seeds. It is elongated structure made up of cellulose.

d. Jute is natural best fibre is obtained from stem of Corchorus Capsularis. It is made up of cellulose and lignin.

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