NIOS Class 12 Biology Chapter 20 Solution – Growth and Development in Plants
NIOS Class 12 Biology Solution Chapter 20 Growth and Development in Plants . NIOS Class 12 Biology Chapter 20 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
INTEXT 20.1
1.) Distinguish between growth and development. .
And: Growth is the increase in number and size of a cell, organ organism whereas Development is Series of qualitative & quantitative changes including growth, differentiation and maturation.
2.) What is differentiation?
Ans: Differentiation is the process of change in cells, tissues or organs to carry out different functions. At this stage, the cells’ structure adapts to carry out particular tasks. Additionally, a group of cells with comparable tasks that are of the same type is known as a tissue.
3.) What role does it play in plant growth and development?
Ans: In differentiation , the cells’ structure adapts to carry out particular tasks. Additionally, a group of cells with comparable tasks that are of the same type is known as a tissue.
INTEXT 20.2
1.) Name the plant hormones concerned with the following: (i) Elongation of cell – Auxin
(ii) Shedding of leaves.- Ethylene
(iii) Breaking seed dormancy .- Abscissic acid
2.) Mention two functions of Auxin
(i) It helps in the elongation of shoot and root tips behind apical meristem
(ii) It promotes cell elongation
3.) What is the difference between dedifferentiation and redifferentiation?
Ans: A permanent, localised qualitative change in the size, biochemistry, structure, and function of cells, tissues, or organs is known as differentiation in plants. While, Plant cells that have undergone dedifferentiation once again lose the ability to divide yet develop to carry out particular activities is called redifferentiation
4.) Which two hormones are essential for vascular tissue differentiation?
Ans: Auxin and Cytokinin are essential for vascular tissue differentiation
INTEXT 20.3
1.) Distinguish between Phototropism and Geotropism
Ans: In Phototropism movement is induced by light e.g. bending of stems towards light
And in Geotropism movement is Induced by gravity e.g. growth of roots towards gravity
2.) Give two examples of turgor movement
Ans: Turgor movements are due to change in the volume of water inside the cell. When more water is present in the cell it is fully expanded and becomes rigid or hard.
Eg: Closure of leaves on fall of darkness and closing leaves of venus fly trap to catch a landing insect
TERMINAL EXERCISE
1.) State the different stages of cellular growth.
Ans:The growth of an organ or an organism occurs in threesuccessive stages. They are
(i) Cell division: Mitosis causes an increase in cell count
(ii) Cell enlargement: Following cell division, each individual cell grows larger as the volume of its protoplasm increases
Cell differentiation (iii): During this phase, the shape of the cells alters to carry out particular tasks. Additionally, a group of similar cell types with comparable functions is known as a tissue.
2.) Distinguish between growth and development.
Ans:
Growth | Development |
Growth in living organisms is not uniform throughout the life span | Development refers to all of these alterations that take place in an organism from its inception to its demise. |
The growth of plants and animals accelerates as they get older. | Development is connected to differentiation and morphogenesis. |
3.) What is a sigmoid growth curve? State the different phases of sigmoid curve.
Ans: The growth rate of the cell number is plotted against time, and a characteristic S-shaped curve is produced. Growth curve or sigmoid growth curve is the term used for this.
There are three growth periods in this curve.
(i) Lag Phase: During this early stage of growth, the pace of growth is extremely slow.
(ii) Log Phase – It exhibits rapid growth and reaches its peak for the entirety of the life span.
(iii) Stationary Phase – At this point, the rate of growth starts to slow down before coming to an end.
4.) Describe the various external factors that affect the growth of plants.
Ans: External factors that affect the plants are asfollows:
Light : light is necessary for reproduction, seed germination, seedling growth, and the differentiation of distinct tissues and organs.
Temperature : The temperature has a direct impact on every metabolic process in plants. Due to chilling and freezing, very low temperatures harm plants, while extremely hot temperatures halt their growth.
Water : utilises it for biological reactions such as photosynthesis and part of it is wasted through transpiration.
Nutrients : Inorganic nutrients are required for every metabolic process. Lack of nutrients has an unfavourable effect on plant growth.
5.) What is vernalisation?
Ans: Vernalization is the technique of exposing a plant to low temperatures in order to speed up the flowering process. As an example, many varieties of wheat, rice, and cotton grow more quickly and blossom earlier when exposed to temperatures between 1 and 10 °C.
6.) Define the term Photoperiodism.
Ans: Photoperiodism is a plant’s biological response to the length of time that light shines on it each day in terms of growth and reproduction (flowering).
7.) What is auxin? What is its role in the growth of plants?
Ans: Auxin is a plant growth hormone that is often produced by the plant’s developing stem and root.
Role of auxin are as follow :
(a) It encourages cell elongation and (b) inhibits the development of lateral buds. The lateral branches of a plant start to grow if the tip is cut off; in the majority of plants, the apical bud suppresses the growth of lateral buds. The term for this is apical dominance.
(c) It delay the leaf fall.
8). State any two functions of Gibberellin?
Ans: In genetically dwarf plants, it aids in the elongation of stems. Gibberellin can beused to make dwarf plants taller.
(b) It awakens dormant seeds and buds.
(c) It causes parthenocarpy. or gives pollination the stimulus it needs.
9.) Explain the role of Cytokinins and Ethylene in growth and development of plants.
Ans: They promote cell differentiation, cell growth, and cell division.
(b) They stop plant parts from ageing.
(c) They prevent apical dominance and promote lateral buds’ development into branches.
Ethylene
A gaseous hormone, ethylene. Ripe fruits, young flowers, and young leaves all contain it.
10.) Distinguish between epigeal germination and hypogeal germination.
Ans: In epigeal germination hypocotyl elongates and cotyledons come out above the soil surface while, In hypogeal germination the epicotyl elongates and cotyledons remain below the soil surface
11.) What is meant by seed germination? Describe the various factors responsible for seed germination.
Ans: The process by which a seed regenerates its metabolic processes and grows in order to produce a new plant is known as germination. The key influences on seed germination include water, temperature, oxygen, light, and hormones.
a) Water : To rip the seed covering, the seed must swell up. A mature seed has extremely little water, according to Heredity. So it is crucial to have a sufficient water supply in order for swelling to result in seed coat rupture.
b) Temperature : Chemical reactions within are accelerated by heat.
c) Oxygen: Oxygen is necessary for releasing energy for the metabolism of the embryo’s growth from the seed’s reserve food.
12.) What is senescence?
Ans: Senescence is the collective term for the deteriorating processes that finally result in the full loss of the organisation and functionality of the plant or its parts.
13.) State any two practical utilities of growth hormones.
Ans: It promotes cell elongation and It helps in elongation of stems in genetically dwarf plants.
14.) What is biological stress? Describe the different types of biological stress.
Ans: Biological stress is the term used to describe any alteration in the environment that could have a negative impact on a plant’s growth or development.
a) Water stress : The plant wilts and develops yellow leaves from a lack of water. Due to a lack of water, several activities in plants, including photosynthesis and respiration, are slowed down, cell growth is inhibited, cell size is distorted, and cell stiffness is lost.
b) Salt stress : The accumulation of excessive amounts of calcium and sodium salts in plant tissues is the principal cause of salt stress. It results in cell dehydration, cell shape modification, and metabolic process disruption.
15.) What is apical dominance? Name the hormone responsible for it.
Ans: In the majority of plants, the apical bud inhibits the growth of lateral buds. The term for this is apical dominance. Auxin is responsible for apical dominance.
16.) What is meant by plant movement? Describe any two types of movement of plants with example.
Ans: Movement of plant or the part of planr away or towards the external environment is plant movement .
Tropic movement is the term for movement in plants or in any part of the plants towards or away from some environmental influences.
Turgor movement : The volume of water inside the cell is changing, which is the cause of these movements.
Also See: Next Chapter No. 20 Question Answer