Question:

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion (A): Libriform fibres are true fibres. 

Reason (R): Libriform fibres develop from non-functional tracheids by reduction.

In the light of the above statements, choose the correct answer from the options given below

Updated On: Aug 4, 2023
  • Both Assertion and Reason are true and Reason is the explanation of Assertion
  • Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • Assertion is true but Reason is false
  • Assertion is false but Reason is true
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The Correct Option is C

Solution and Explanation

When the fibres possess very thick walls and reduced simple pits, they are known as libriform wood fibres because of their similarity to phloem fibres. Libriform wood fibres chiefly occur in woody dicotyledons. There are many transitional forms between the fibres and normal tracheids. These transitional forms are designated as fibre tracheids. A line of demarcation cannot be drawn between tracheids and fiber tracheids.
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Concepts Used:

Anatomy of Dicotyledonous and Monocotyledonous Plants

Dicot Root:

  • Dicot plants have the taproot system.
  • The outermost layer is called the epidermis. The epidermal cells sometimes project out which appear as the root hairs.
  • The epidermis is followed by the multi-layered cortex, loosely made of the parenchyma cells with intercellular spaces.
  • The inner layer of the cortex is called endodermis, which is tightly packed by the barrel shaped-cells.
  • Endodermis is followed by pericycle, which are a few layers of thick-walled parenchyma cells.
  • In dicots, the central pith is not distinct.
  • There are two to four xylem and phloem.
  • The xylem and phloem are remarked by a layer of parenchymatous cells known as conjunctive tissue.

Monocot Root:

Monocot roots do not show much difference in the anatomy from that of the dicot roots.

  • Monocot plants possess an adventitious root system.
  • As in the dicots, the epidermis forms the outermost layer, followed by cortex, pericycle, endodermis, vascular bundles (xylem and phloem) and pith (random order).
  • Pith is conspicuous and large.
  • The number of xylem in a monocot is six or more.
  • Secondary growth is not seen in the monocot plants.