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Chapter 7: Plant Growth and Mineral Nutrition [ Exercise,Solutions,Notes ]

Plant Growth and Mineral Nutrition [ Exercise,Solutions,Notes ]

Plant Growth and Mineral Nutrition [ Exercise,Solutions,Notes ]

Multiple choice question.

Exercise | Q 1.01 | Page 151
Which of the hormones can replace vernalization?
Auxin
Cytokinin
Gibberellins
Ethylene
Solution:
Gibberellins

Exercise | Q 1.02 | Page 151
 The principle pathway of water translocation in angiosperms is ______
Sieve cells
Sieve tube elements
Xylem
Xylem and phloem
Solution:
The principle pathway of water translocation in angiosperms is Xylem.


Exercise | Q 1.03 | Page 151
 Abscisic acid controls ______.
cell division
leaf fall and dormancy
shoot elongation
cell elongation and wall formation
Solution:
Abscisic acid controls leaf fall and dormancy.


Exercise | Q 1.04 | Page 151
 Which is employed for the artificial ripening of banana fruits?
Auxin
Ethylene
Cytokinin
Gibberellin
Solution:
Ethylene

Exercise | Q 1.05 | Page 151
 Which of the following is required for stimulation of flowering in the plants?
Adequate oxygen
Definite photoperiod
Adequate water
Water and minerals
Solution:
Definite photoperiod


Exercise | Q 1.06 | Page 151
For short-day plants, the critical period is
light
dark/ night
UV rays
both light and UV rays
Solution:
For short-day plants, the critical period is dark/ night.


Exercise | Q 1.07 | Page 151
Which of the following is day-neutral plant?
a. Tomato
b. Cotton
c. Sunflower
d. Soybean
Solution:
a. Tomato and c. Sunflower


Exercise | Q 1.08 | Page 151
 Essential macroelements are ____________.
manufactured during photosynthesis
produced by enzymes
absorbed from soil
produced by growth hormones
Solution:
Essential macroelements are absorbed from soil.

Exercise | Q 1.09 | Page 151
Function of Zinc is ______.
closing of stomata
biosynthesis of 3-IAA
synthesis of chlorophyll
oxidation of carbohydrates
Solution:
Function of Zinc is biosynthesis of 3-IAA.

Exercise | Q 1.1 | Page 151
Necrosis means ______.
yellow spots on the leaves
death of tissue
darkening of green colour in leaves
wilting of leaves
Solution:
Necrosis means death of tissue.

Exercise | Q 1.11 | Page 151
Conversion of nitrates to nitrogen is called ______
ammonification
nitrification
nitrogen fixation
denitrification
Solution:
Conversion of nitrates to nitrogen is called denitrification.

Exercise | Q 1.12 | Page 151
How many molecules of ATP are required to fix one molecule of nitrogen?
12
20
6
16
Solution:
16


Very Short Answer Question,:

Exercise | Q 2.01 | Page 151
Enlist the phases of growth in plants?
Solution:
Three phases of growth in plants are:
i. Phase of cell division/ formation
ii. Phase of cell enlargement/ elongation
iii. Phase of cell maturation/ differentiation.

Exercise | Q 2.02 | Page 151
 Give the full form of IAA?
Solution:
IAA: Indole-3-acetic acid

Exercise | Q 2.03 | Page 151
What does it mean by ‘open growth’?
Solution:
The form of growth where in new cells are being constantly added to the plant body by the activity of the meristem is called the open growth.

Exercise | Q 2.04 | Page 151
Which is the plant stress hormone?
Solution:
Abscisic acid (ABA) is the plant stress hormone

Exercise | Q 2.05 | Page 151
What is denitrification?
Solution:
i. Denitrification is the process in which anaerobic bacteria convert soil nitrates back into nitrogen gas.
ii. Denitrifying bacteria removes fixed nitrogen i.e. nitrates from the ecosystem and returns it to the atmosphere in an inert form.
iii. Denitrifying bacteria include Bacillus spp., Paracoccus spp. and Pseudomonas denitrificans. They transform nitrates to nitrous and nitric oxides and ultimately to gaseous nitrogen.
2NO3 → 2NO2 → 2NO → N2

Exercise | Q 2.06 | Page 151
 Name the bacteria responsible for conversion of nitrite to nitrate.
Solution:
Chemoautotrophs like Nitrobacter are responsible for conversion of nitrite to nitrate.

Exercise | Q 2.07 | Page 151
What is role of gibberellin in rosette plants?
Solution:
Gibberellin promotes bolting i.e. elongation of internodes just prior to flowering in plants with rosette habit e.g. beet, cabbage

Exercise | Q 2.08 | Page 151
Define vernalization.
Solution:
The low-temperature treatment or chilling treatment of germinating seeds or seedlings to promote early flowering in plants is called vernalization. It was evidenced by Klippart (1918).

Exercise | Q 2.09 | Page 151
Define photoperiodism.
Solution:
The relative length of the day which is crucial in the growth and development of flowers is termed as photoperiodism

Exercise | Q 2.1 | Page 151
What is a grand period of growth?
Solution:
The total time (period) required for all phases to occur, is called Grand Period of Growth.


Short Answer Question,:

Exercise | Q 3.1 | Page 152
Write a short note on Differentiation.
Solution:
1. It is maturation of cells derived from the apical meristem of root and shoot.
2. Permanent change in structure and function of cells leading to maturation is called differentiation.
3. During cell differentiation, the cell undergoes few to major anatomical and physiological changes.
4. For e.g. Parenchyma in hydrophytes develops large schizogenous interspaces for mechanical support, buoyancy and aeration.
5. Cells lose the capacity to divide and redivide and mature.

Exercise | Q 3.1 | Page 152
Write a short note on Re-differentiation.
Solution:
1. The cells produced by dedifferentiation once again lose the capacity to divide and mature to perform a specific functions. This is called a re-differentiation.
2. For e.g. secondary xylem and secondary phloem are formed from dedifferentiated cambium present in the vascular bundle.

Exercise | Q 3.2 | Page 152
 Differentiate between Arithmetic and Geometric growth.
Solution:
Arithmetic growthGeometric growth
After mitosis one of the daughter cell continues to divide and the other cell takes part in the differentiation and maturation.After mitosis both the daughter cells continue to divide and re-divide repeatedly.
On plotting the growth against time, a linear curve is obtained.On plotting the growth against time, a sigmoid curve is obtained.

Exercise | Q 3.3 | Page 152
Enlist the role and deficiency symptoms of Nitrogen.
Solution:
Nitrogen:
a. Role: Constituent of proteins, nucleic acids, vitamins, hormones, coenzymes, ATP, chlorophyll.
b. Deficiency symptom: Stunted growth, chlorosis

Exercise | Q 3.3 | Page 152
Enlist the role and deficiency symptoms of Phosphorus.
Solution:
Phosphorus:
a. Role: Constituent of cell membrane, certain proteins, all nucleic acids, and nucleotides required for all phosphorylation reactions.
b. Deficiency symptom: Poor growth, leaves dull green.

Exercise | Q 3.3 | Page 152
 Enlist the role and deficiency symptoms of Potassium.
Solution:
1. Critical photoperiod is the length of photoperiod above or below which flowering occurs. Short Day Plants usually flower during winter and late summer when day length is shorter than the critical photoperiod.

2. These are called long night plants because they require long uninterrupted dark period/ night for flowering.

3. If the dark period is interrupted even by a flash of light, SDP will not flower.

4. Some of the short-day plants are Dahlia, Tobacco, Chrysanthemum, Soybean (Glycine max), Cocklebur (Xanthium), cotton, etc.

Exercise | Q 3.4 | Page 152
What is short day plant? Give any two examples.
Solution:
1. Critical photoperiod is the length of photoperiod above or below which flowering occurs. Short Day Plants usually flower during winter and late summer when day length is shorter than the critical photoperiod.

2. These are called long night plants because they require long uninterrupted dark period/ night for flowering.

3. If the dark period is interrupted even by a flash of light, SDP will not flower.

4. Some of the short-day plants are Dahlia, Tobacco, Chrysanthemum, Soybean (Glycine max), Cocklebur (Xanthium), cotton, etc.

Exercise | Q 3.5 | Page 152
 Define vernalization.
Solution:
The low-temperature treatment or chilling treatment of germinating seeds or seedlings to promote early flowering in plants is called vernalization. It was evidenced by Klippart (1918).

Exercise | Q 3.5 | Page 152
Give its significance of vernalization.
Solution:
1. Chouard (1960) defined vernalization as the acceleration of the ability to flower by chilling treatment.
2. The term vernalization was coined by T.D Lysenko (1928) for the effect of low temperature on flowering in plants.
3. It is an influence of temperature on development and flowering.
4. Many plants such as cereals, crucifers require a period of cold treatment for flowering.
5. It is the method of inducing early flowering in the plants by pretreatment to their seeds/ seedlings at low temperatures (1-6ºC for one to one and half months’ duration).
6. The site of vernalization is believed to shoot apical meristem.
7. Generally, vernalization is effective at the seed stage in annual plants.
8. It was suggested by Melchers (1939) that vernalization initiates a stimulus for the formation of a hormone called vernalin.

9. Significance of vernalization:
a. Crops can be produced earlier.
b. Crops can be cultivated in regions where they do not grow naturally.

Long Answer Question

Exercise | Q 4.1 | Page 152
Explain sigmoid growth curve with the help of diagram.
Solution:
1. The curve obtained when a graph of growth rate against time is plotted for three phases of growth is called as a sigmoid curve.

2. Growth rate differs with three distinct phases of growth.

3. In the Lag phase, the growth rate is slow.

4. In Exponential (Log) phase, growth rate is faster and reaches its maximum.

5. In Stationary phase, growth rate gradually slows down.

Exercise | Q 4.2 | Page 152
Describe the types of plants on the basis of photoperiod required, with the help of suitable examples.
Solution:
Based on the photoperiodic response, plants were classified into three categories viz. Short Day Plants (SDP), Long Day Plants (LDP) and Day Neutral Plants (DNP).

1. Short Day Plants (SDP):

i. Critical photoperiod is the length of photoperiod above or below which flowering occurs. Short Day Plants usually flower during winter and late summer when day length is shorter than the critical photoperiod.
ii. These are called long night plants because they require long uninterrupted dark period/ night for flowering.
iii. If dark period is interrupted even by a flash of light, SDP will not flower.
iv. Some of the short-day plants are Dahlia, Tobacco, Chrysanthemum, Soybean (Glycine max), Cocklebur (Xanthium), cotton, etc.

2. Long Day Plants (LDP):

i. Plants that flower during summer are called long-day plants.
ii. They require a longer duration of light than the critical photoperiod, for flowering.
iii. They are called short night plants as they require a short dark period.
iv. When long dark period is interrupted by a brief flash of light, LD plants can flower e.g. pea, radish, sugar beet, cabbage, spinach, wheat, poppy, etc.

3. Day Neutral Plants (DNP):

a. These plants flower throughout the year-round, independent of the duration of light (photoperiod).
b. They do not require specific photoperiod to flower.
c. Therefore, they are called day-neutral plants e.g. Cucumber, tomato, sunflower, maize, balsam, etc.


Exercise | Q 4.3 | Page 152
Explain biological nitrogen fixation with example.
Solution:
Biological nitrogen fixation:

i. It is carried out by prokaryotes called as ‘Nitrogen fixers’ or Diazotrophs’.
ii. It accounts for nearly 70% of natural nitrogen fixation.
iii. Nitrogen fixers are either symbiotic or free living.

iv. Symbiotic N2 fixation:
The best-known nitrogen-fixing symbiotic bacterium is Rhizobium. This soil living/ dwelling bacterium forms root nodules in plants belonging to the family Fabaceae e.g. beans, gram, groundnut etc.

v. Azotobacter, Azospirillum is free-living nitrogen-fixing bacteria.
vi. The cyanobacteria fix a significant amount of nitrogen in specialized cells called heterocysts.
vii. Nitrogen fixation is high energy-requiring process and nitrogen fixers use 16 molecules of ATP to fix each molecule of nitrogen to form ammonia.
N2 + 8H+ + 8e- + 16ATP → 2NH3 + H2 + 16ADP + 16Pi

plant growth and mineral nutrition class 12 notes pdf download

 Plant growth : Growth is one of the characteristic features of living organisms. Growth as a phenomenon has two aspects viz. quantitative and qualitative. Quantitative aspect speaks for an increase in the length, breadth, size, volume, body mass or dry weight and number of cells. Growth as a quantitative change is a final end product of successive metabolism. 

Qualitative aspect talks about the change in the nature of growth where development is an ordered change or progress while differentiation leads to higher and more complex state. Growth thus can be defined as permanent, irreversible increase in the bulk of an organism, accompanied by the change of form. In multicellular (vascular) plants, growth is indeterminate and occurs throughout the life indefinitely.

 It is restricted to some specific region called meristems which are the regions where new cells are constantly and continuously produced. Meristems are of three types based on location viz. Apical, Intercalary and Lateral.

Phases of growth : The cells in the meristem divide, enlarge and get differentiated. Corresponding to these three stages, there are three phases of growth : A. Phase of cell division/ formation : Cells of meristem are thin walled, non-vacuolated having prominent nucleus and granular cytoplasm. Meristematic cell undergoes mitotic division to form two new cells. One cell remains meristematic and the other cell undergoes enlargement and differentiation. In this phase, rate of growth occurs at a slower pace (Lag phase).

B. Phase of cell enlargement/ elongation : The newly formed cell becomes vacuolated, osmotically active and turgid due to absorption of water. The turgidity results in the enlargement of cell - both lengthwise and breadthwise. In this phase new wall materials and other materials are synthesized to cope up with the enlargement. The growth rate in this phase occurs at an accelerated pace (exponential or Log phase). 

C. Phase of Cell maturation/ differentiation : The enlarged cell now becomes specialized to perform specific fuction and attains maturity - both morphological and physiological. In this phase, rate of growth slows down and comes to a steady state (stationary phase). 

Conditions for Growth : The different environmental and physiological conditions necessary for the growth include - Water, supply of nutrients,

temperature, oxygen, Carbon/ Nitrogen ratio, gravitational force, light and growth hormones. The chief conditions are explained below : 

Water is the essential component of protoplasm and maintains turgidity of the cell. It acts as aqueous medium for biochemical reactions. Microelements and Macroelements are nutrients required for the proper growth of the plant. Optimum Temperature ranges between 25-350 C. Oxygen is essential for respiration and the release of energy. Light is very much essential for germination of seed and photosynthesis. Gravitational force decides the direction of growth of the shoot and root.

Growth Rate and types of growth : Growth rate : It is the increased growth per unit time. It is also called efficiency index. Rate of growth can be measured by an increase in the size and area of different plant organs like leaf, flower and fruits. The ratio of change in the cell number (dn) over the time interval (dt) is called Absolute growth rate (AGR). Alternatively, it is the measurement and comparison of total growth per unit time.

The AGR, when divided by total number of cells present in the medium, gives Relative growth ratio (RGR). Alternatively, RGR refers to the growth of a particular system per unit time, expressed on a common basis or it is the ratio of growth in the given time/ initial growth.

a. Arithmetic growth : Here, rate of the growth is constant and an increase in the growth occurs in arithmetic progression. i.e. 2, 4, 6, 8 cms etc.In this type of growth, the rate of growth is constant. After mitosis one of the daughter cell continues to divide and the other cell takes part in the differentiation and maturation. e.g. elongation of root at a constant rate, best explains arithmetic growth. Linear curve is obtained when growth rate is plotted against the time. Arithmetic growth is expressed mathematically by an equation, It is expressed as,

b. Geometric growth : Cell divides mitotically into two. Here, both the daughter cells continue to divide and redivide repeatedly. Such growth is called geometric growth. Here, growth rate is slow

Minerals salt absorption : Most minerals in the soil are charged particles hence, they can not pass across cell membrane. Hence most of the minerals are absorbed actively with the expenditure energy. Minerals can also be absorbed passively without expenditure of energy. Mineral ion absorption is independent of water absorption. Mineral ion absorption can occur in two ways

a. Passive Absorption : Movement of mineral ions into the root occurs by diffusion. Molecules or ions diffuse from a region of their higher concentration to a region of their lower concentration. The movement of mineral ions into root cells as a result of diffusion is without expenditure of energy is called passive absorption. Passive absorption can take place by direct ion-exchange, in direct ion-exchange mass flow and Donnan equilibrium

b. Donnan equilibrium : It is based on the assumption that certain negatively charged ions, after their entry into the cell, become fixed on the inner side of the cell membrane and can not diffuse outside through the cell membrane. Therefore, additional mobile cations are required to balance these fixed anions. Obviously concentration of cations become more due to accumulation. This kind of passive absorption of anions/ cations from cell exterior against their own concentration gradient in order to neutralize the effect of cations/ anions, is called Donnan equilibrium. 

Active Absorption: Uptake of mineral ions against concentration gradient, is called active absorption, such movement requires an expenditure of energy by the absorbing cell. This energy is derived from respiration and is supplied through ATP. When the roots are deprived of oxygen, they show a sudden drop in active absorption of minerals. The mineral ions accumulated in the root hair pass into the cortex and finally reach the xylem.

 The minerals in the xylem are then carried along with water to other parts of the plant along the transpiration stream and are subsequently assimilated into organic molecules and then redistributed to other parts of the plant through the phloem

plant water relations class 12 exercise । plant growth and mineral nutrition notes


Balbharati solutions for Biology 12th Standard HSC for Maharashtra State Board
Chapter 1: Reproduction in Lower and Higher Plants
Chapter 2: Reproduction in Lower and Higher Animals
Chapter 3: Inheritance and Variation
Chapter 4: Molecular Basis of Inheritance
Chapter 5: Origin and Evolution of Life
Chapter 6: Plant Water Relation
Chapter 7: Plant Growth and Mineral Nutrition
Chapter 8: Respiration and Circulation
Chapter 9: Control and Co-ordination
Chapter 10: Human Health and Diseases
Chapter 11: Enhancement of Food Production
Chapter 12: Biotechnology
Chapter 13: Organisms and Populations
Chapter 14: Ecosystems and Energy Flow
Chapter 15: Biodiversity, Conservation and Environmental Issues

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