Tag: root - external morphology

Questions Related to root - external morphology

Quiescent centre is found in

botany root - external morphology morphology of the root root system in plants root

  1. Stem tip

  2. Root tip

  3. Leaf tip

  4. None of the above

Show answer
Correct Option: B
Explanation:

A quiescent centre is a small group of cells with low mitotic activity (no cell division). Quiescent centre is to be found at the tips of growing roots, in the root meristem and are surrounded by groups of dividing cells.
So, the correct answer is 'Root tip'.

The root cap is not used in absorption of water due to

botany root - external morphology morphology of the root root system in plants root

  1. Presence of root hairs

  2. Absence of root hairs

  3. Its presence in elongation zone

  4. None of the above

Show answer
Correct Option: B
Explanation:

The external protective layer in dicot root is called as epiblema or piliferous layer. The cells of epidermis extend into unicellular root hairs. In the root cap there is no root hair present. In absence of root hairs water absorption is not possible. So, the correct answer is option B.

The layer of cells outside the phloem meant for giving rise to the root branches is called as

botany root - external morphology morphology of the root root system in plants root

  1. Cambium

  2. Carpus

  3. Endodermis

  4. Pericycle

Show answer
Correct Option: D
Explanation:

The vascular cylinder is interior to the endodermis and is surrounded by the pericycle, a layer of cells that gives rise to branch roots. 
Pericycle is the region consisting of one or more layers of cells, found external to central cylinder (stele). Pericycle is composed of parenchyma cells or sclerenchyma cells or both. Lateral branches and phellogen arise from pericycle.

Root hairs are found

botany root - external morphology morphology of the root root system in plants root

  1. In the zone of maturation

  2. Adventitious roots

  3. On the root cap

  4. Apical meristem

Show answer
Correct Option: A
Explanation:
A root hair, or absorbent hair, the rhizoid of a vascular plant, is a tubular outgrowth of a trichoblast, a hair-forming cell on the epidermis of a plant root.
Root hair cells vary between 15 and 17 micrometres in diameter, and 80 to 1,500 micrometres in length. 
They are found only in the zone of maturation, and not the zone of elongation, possibly because any root hairs that arise are sheared off as the root elongates and moves through the soil.

The function of root cap is to

botany root - external morphology morphology of the root root system in plants root

  1. Protect the root tip

  2. Protect the root hairs

  3. Cover the root

  4. Growth of the root

Show answer
Correct Option: A
Explanation:
  • At the terminal region of the root tip is a cup-like or a thimble-like structure called the root cap which is formed from calyptrogen (specialized internal meristematic cells).
  • It is also known as calyptra.
  • It contains statocytes which help in gravity perception in plants that help in the growth of root towards the soil.
  • The root apex is protected by this root cap as it penetrates into the soil.
The root cap is formed by a specialized internal meristematic which is part of the histogen and is called calyptrogen
So, the correct answer is 'Protect the root tip'

Root cap regenerates$/$ dead torn cells of root cap are replaced by the activity of

botany root - external morphology morphology of the root root system in plants root

  1. Plerome

  2. Dermatogen

  3. Calyptrogen

  4. Periblem

Show answer
Correct Option: C
Explanation:
  • At the terminal region of the root tip is a cup-like or a thimble-like structure called the root cap which is formed from calyptrogen (specialized internal meristematic cells).
  • The root apex is protected by this root cap.
  • The root cap is formed by a specialized internal meristematic which is part of the histogen and is called calyptrogen.
  • The calyptrogen continuously divide to form the root cap and also helps in the regeneration of root cap in case of injury.
  • So, the correct answer is 'Calyptrogen'.

Quiescent centre shows

botany root - external morphology morphology of the root root system in plants root

  1. Rapid divisions

  2. High metabolic activity

  3. Little meristematic activity

  4. Development of lateral appendages

Show answer
Correct Option: C
Explanation:
  • The quiescent centre is that part of the root-promeristems that contains the initials of epidermis, cortex and stele.
  • These cells divide less frequently as they are inactive and are present at the pole of cortex and stele.
  • The cells with QC have small dictyosomes, nuclei and nucleoli with little cytoplasm.
  • These cells also have little endoplasmic reticulum, mitochondria and contain low concentrations of RNA, DNA and protein than the other cells of the root apex.
  • So, the correct answer is 'Little meristematic activity'.

Casparian thickenings are found in the cells of

botany root - external morphology morphology of the root root system in plants root

  1. Pericycle of the root

  2. Endodermis of the root

  3. Pericycle of the stem

  4. Endodermis of the stem

Show answer
Correct Option: B
Explanation:

The radial walls of the endodermis are marked by characteristic thickenings, called the casparian strips. These thickenings contain lignin, suberin and phenolic oxidation products that gives the strips a dark colour. The endodermis is a typical cell layer of roots. In roots, it is localized at the periphery of the vascular cylinder. 

Root hairs develop from

botany root - external morphology morphology of the root root system in plants root

  1. Region of maturation

  2. Zone of elongation

  3. Meristematic region

  4. Region of mature cells

Show answer
Correct Option: A
Explanation:

This region represents the zone of differentiation or maturation because different types of primary tissues differtiate or mature in this region. Root hair zone is 1 - 6 cm in length. Most of the water absorption occurs in this region. Some of the outer cells of this zone give rise to lateral tubular outgrowths called root hairs. The root hairs increase the exposed surface of the root for absorption.

Root hairs occur in the zone of 

botany root - external morphology morphology of the root root system in plants root

  1. Cell division

  2. Cell elongation

  3. Cell maturation

  4. Mature cells

Show answer
Correct Option: C
Explanation:

Root consist of four parts:-

  1.  Root cap which protects the root and secrete mucilage which lubricates the root.
  2. Region of meristematic activity where apical meristem is present and increase the length of root.
  3. Region of elongation where the newly-formed cells increase in length, thereby lengthening the root.
  4. Region of maturation that bears unicellular root hairs which increases the surface area and helps in the absorption of water.
So, the correct option is 'Cell maturation'.