Tag: shoot and root apex

Questions Related to shoot and root apex

The term quiescent centre or zone was proposed by

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Schmidt

  2. Foster

  3. Clowes

  4. Nageli

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Correct Option: C
Explanation:
  • The quiescent centre is that part of the root-promeristems of higher plants 
  • They may consist of four cells (minimum) or can go up to 600 cells which show very low mitotic activity.
  • In closed meristem, QC is hemispherical in shape whereas, in open meristem it is disc-shaped.
  • The QC is unusual in the centre of shoots.
  • Frederick Albert Lionel Clowes was a British biologist.
  • He proposed the term Quiescent centre or cytogenerative centre which represents the region of an apical meristem of the root where cell division is very slow.
  • So, the correct answer is 'Clowes'

Cells of quiescent centre are characterized by

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Dense cytoplasm and prominent nuclei

  2. Light cytoplasm and small nuclei

  3. Dividing regularly to add to the corpus

  4. Dividing regularly to add to tunica

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Correct Option: B
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 'Light cytoplasm and small nuclei'.

Histogen tissues are classified on the basis of _________.

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Plane of division

  2. Type of cells they form

  3. Position

  4. Origin

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Correct Option: B
Explanation:
  • The shoot apical meristem (SAM) form three distinct meristematic zones called the histogens.
  • These histogens are present at the growing tips of a stem or a root.
  • These tips consist of three histogens based on the type of cells they form.
  • Each of these histogens gives rise to tissues which are different from one another- dermatogen, periblem, plerome (principle tissues)
  • The dermatogen or the outer layer gives rise to the epidermis, periblem or middle layer gives rise to the cortex as well as the endodermis, plerome or the inner layer gives rise to vascular tissues.
  • This is called histogen theory which was proposed by Hanstein in 1870.
  • So, the correct answer is 'Type of cells they form'

Quiescent centre is the zone of

biology anatomy of flowering plants theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Least mitotic activity in the root apex

  2. Least mitotic activity in the shoot apex

  3. Maximum mitotic activity in the root apex

  4. Maximum mitotic activity in the shoot apex

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Correct Option: A
Explanation:

A zone of inactive cells is present in the central part of the root apex called quiescent centre.

Reproductive shoot apex is

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Conical or dome shaped

  2. Broad

  3. Broad and flat

  4. Narrow

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Correct Option: C
Explanation:
  • Reproductive shoot apex- At the time of flowering, the vegetative shoot apex transforms into reproductive shoot apex.
  • The summit zone of reproductive shoot apex is active as the rate of cell division is greater and it forms stamens and carpels.
  • Whereas, the flank zone is less active in reproductive shoot apex and it forms sepals and petals.
  • The Reproductive shoot apex is Broad and flat.
  • So, the correct answer is 'Broad and flat'.

Histogen theory was proposed by

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Bailey

  2. Haberlandt

  3. Hanstein

  4. Schmidt

Show answer
Correct Option: C
Explanation:

The histogen theory was given by Hanstein (1870), According to this, there are 3 groups of initials in the shoot apex. According to Hanstein, the three principal tissues of the root; vascular cylinder, cortex and epidermis originate from three groups of initial cells or histogens, in the apical meristem plerome, periblem and dermatogen respectively. A fourth histogen, the calyptrogen produces the root cap.
Therefore, the correct answer is option C.  

Tunica corpus theory is connected with

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Root apex

  2. Root cap

  3. Shoot apex

  4. Secondary growth

Show answer
Correct Option: C
Explanation:
  • The Tunica-corpus theory explains the planes of cell division in the shoot apex.
  • It was proposed by Schmidt in 1924.
  • It was proposed on the basis of the study of shoot apex.
  • This theory is applicable only to shoot apex and not to root. 
  • This theory divides the region (shoot apex) into two tissue zones known as tunica and corpus.
  • The shoot apex is composed of two layers of cells of tunica and corpus  (layer L1, L2 and L3 to denote the outer layer of tunica, the inner layer of tunica and corpus respectively).
  • The plasmodesmata connections exist between the cells of tunica and corpus.
  • So, the correct answer is 'Shoot apex'

According to histogen theory, epidermis is formed by

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Dermatogen

  2. Protoderm

  3. Periblem

  4. Plerome

Show answer
Correct Option: A
Explanation:
  • The histogens at the shoot and root tip in plants as these are derived from the apical meristematic tissues according to the histogen theory given by Hanstein.
  • It consists of three distinct layers:-
  1. Dermatogen is the primary meristem that forms the outer most layer of a plant or a plant part and forms the epidermis.
  2. Periblem is a primary meristem which is located between the plerome and the dermatogen and it forms the cortex.
  3. Plerome is the primary meristem that forms the central core of a plant or plant part which gives rise to the stele (includes the vascular tissue, pith and pericycle).
  • The part of plerome from which vascular tissues are formed is called procambium.
  • So the correct answer is 'Dermatogen'

Concept envisaging three zones of cells in root and stem apices is

botany plant tissues - internal morphology and anatomy theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Histogen theory

  2. Tunica corpus theory

  3. Meristem theory

  4. Dermatogen theory

Show answer
Correct Option: A
Explanation:
  • The shoot apical meristem (SAM) consists of three distinct meristematic zones called the Histogens.
  • This is called histogen theory of tissues which was proposed by Hanstein in 1870 explains the activity of both the root and shoot apical meristem.
  • These histogens are present at the growing tips of a stem or a root.
  • These tips consist of three histogens and each of these histogens gives rise to tissues which are different from one another
1) Dermatogen is the primary meristem that forms the outer most layer of a plant or a plant part and forms the epidermis.
2) Periblem is a primary meristem which is located between the plerome and the dermatogen and it forms the cortex.
3) Plerome is the primary meristem that forms the central core of a plant or plant part which gives rise to the stele (includes the vascular tissue, pith and pericycle).
  • The part of plerome from which vascular tissues are formed is called procambium.
So, the correct answer is 'Histogen theory'

In the root apex, that meristem from which the root cap developsindependently of all other initials of the apical meristem is known as _______________.

biology anatomy of flowering plants theories of meristematic cell development theories of shoot apical meristem development shoot and root apex

  1. Calyptrogen

  2. Casparian strip

  3. Columella

  4. Corpus

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Correct Option: A