Ch.7 Plant Growth and Mineral Nutrition

 

Prof.Dr.Sadhana Nikam
Vice Principal
Rashtriya Jr. College, Chalisgaon
Biology Subject
Notes of XII Science

Ch.7 Plant Growth and Mineral
Nutrition

Introduction :

*Growth has two aspects as quantitative and qualitative.

*Growth can be defined as permanent  irreversible  increase  in weight of an

 organism with change in their form.

7.9  Growth Hormones :

Q. Who coined the term Hormone(1 Mark)

Starling first coined the term hormone in 1906. 

Q.Define Growth hormones (1 Mark)

The internal factors that influence growth are called Growth Hormones. 

Q.Why  Growth hormones  are  called  Growth regulators     (1 Mark)  

As Growth hormones  inhibit  promote  or  modify  the plant growth  they  are

called  as  Growth  regulators.  

Q. Enlist  the  names  of  Growth  Promoters (1 Mark)

      

Growth  promoters  are  Auxins, Gibberellins (GA) and  Cytokinins (CK).

Q. Enlist  the  names  of  Growth  inhibitors (1 Mark)

Growth  inhibitors  are  Ethylene  and  Abscissic  acid 

Q.Define Plant  Hormones (1 Mark)

Organic substances produced naturally in higher plants which affect growth or

other physiological function away  from its site of production and active in very

minute concentration are called Plant  Hormones 

(Thimann and  Pincus,1948)

Auxins :

Q. Who first  used the  term  Auxins (1 Mark)

F.W.Went  in 1931, first  used  the  term  Auxins.

Q. From  which  source  Auxins  isolated (1 Mark)

Auxins  were  isolated  from  urine  of  a  person  suffering  from  Pellagra.

Q. Which  is important  natural  auxin (1 Mark)

The most  common  and  important  natural  auxin  is  Indole-3-acetic  acid (IAA).

Q. Give full  form  of  IAA (1 Mark)

The  full form  of  IAA  is  Indole - 3 - acetic  acid.

Q.Which is the primary precurser of IAA ( 1 Mark)

•   Tryptophan is the primary precurser of IAA in plants. 

Q. Give  applications  of  Auxins (3 Marks)

•      1. Auxins promote  cell  division  and  cell  elongation.

•      2. Auxins  promote  root  initiation.

•      3. Auxins  promote  apical  dominance.

•      4. Auxins  stimulate  parthenocarpy  in orange, lemon, grapes.

•      5. Auxins like 2,4-D kills dicot  weeds without  affecting  monocot crop plants.

•      6. Auxins  break  seed  dormancy  and  promote  seed  germination.

•      7. Auxins  prevent  premature  fruit  drop  in  apple, pear  and  oranges.

 Gibberellins :

Q. From  which  fungus  Gibberellins  were  isolated (1 Mark)

•      Gibberellins  were  isolated  from  the  fungus  Gibberella  fujikuroi  by  Japani  scientist  Kurosava.

Q. Which  is  common  Gibberellin (1 Mark)

•      GA 3  is  most  common  and  biologically  active  Gibberellin.

Q. Give  applications  of  Gibberellins( 3 Marks)

•      1. Gibberellins  stimulate  cell  elongation.

•      2. Gibberellins  break  seed  dormancy.

•      3. Gibberellins  promote  seed  germination  in monocot  plants.

•      4. Gibberellins  promote  leaf  expansion.

•      5. Gibberellins  increase  fruit  size  and  bunch length  of grapes.

•      6. Gibberellins  stimulate  parthenocarpy.

•    7. Gibberellins  promote  bolting  i.e. internode  elongation  in rosette plant like 

        cabbage  and  beet.

•      8. Gibberellins  break  genetic  dwarfism.

Cytokinin :

 Q. Which  growth  hormone  promote  cell  division.(1 Mark)

•      Cytokinin promote  cell  division.

Q. Who  coined  the  term  cytokinin.(1 Mark)

•      Letham  coined  the  term  cytokinin.

Q . Who  discovered  first  cytokonin.(1 Mark)

•      First  cytokinin  was  discovered  by  Skoog  and  Miller  in  1954  from  culture  of  Nicotiana  tobaccum (Tobacco)

Q. Which  is  the  first  natural  cytokinin.( 1 Mark)

•      First  natural  cytokinin  is  Zeatin.

 Q. Which  is  synthetic  cytokinin.(1 Mark)

•      6- benzyl  adenine  is  a synthetic  cytokinin.

Q.Give  applications  of  Cytokinin (3 Marks)

•      1.Cytokinin  promote  cell  division  and  cell  enlargement.

•      2. Cytokinin  control  apical  dominance.

•      3. Cytokinins  delay  senescence  or  ageing  process.

•      4. Cytokinin  break  seed  dormancy  and  promote  seed  germination.

•      5. Cytokinin delay  abcission  process  in  plant  organs.

•      6. Cytokinin  and  auxin  together  stimulate  organogenesis.

•      7. Cytokinin  stimulate  RNA  synthesis .

•      8. Cytokinin  and  auxin  acclerate  the  rate  of  mitosis.

Ethylene :

 Q.Which  is  gaseous  hormone(1 Mark)

•      Ethylene  is  a  gaseous  hormone.

 Q. Which  is  the  source  of  Ethylene (1 Mark)

•      Ethephon  is  the  source  of  Ethylene.

Q. Give  applications  of  Ethylene (3 Marks)

•      1. Ethylene  promote  fruit  ripening  in  bananas, apples  and  mangoes.

•      2. Ethylene  break  seed  and  bud  dormancy.

•      3. Ethylene  promote  senescence  and  abcission.

•      4. Ethylene  causes  apical  dominance.

•      5. Ethylene  inhibit  flowering  except  in  pineapple.

•      6. Ethylene  causes  epinasty  (drooping ) of  leaves  and  flowers.

•      7. Ethylene  stimulate  initiation of  lateral  roots.

•      8. Ethylene  causes  degreening  effect  in  banana  and  citrus  fruits.

Abscissic  Acid :

Q. Which is  growth  inhibiting  hormone( 1 Mark)

     Abscissic  Acid  is  a  natural  growth  inhibiting  hormone.

Q. Give  applications  of  ABA (3 Marks)

1.     ABA  promote  abcission  and  dormancy.

2.     ABA  promote  senescence  of  leaves, flowers  and  fruits.

3.     ABA  inhibit  cell division  and  cell  elongation.

4.  ABA  cause  closing  of  stomata  to  prevent  transpiration.

5.  ABA  act  as  a  stress  hormone  by  promoting  plants  to  overcome  adverse

     environmental  conditions.

6.  ABA  inhibit  flowering  in  long day  plants  but  stimulate  flowering  in  short

     day  plants.

7.     ABA  inhibit  RNA  and  protein  synthesis.

Remaining units are not involved in syllabus during 2020-2021