RBSE Solutions for Class 12 Biology Chapter 1 Reproduction in Angiospermic Plants
RBSE Solutions for Class 12 Biology Chapter 1 Reproduction in Angiospermi
Rajasthan Board RBSE Class 12 Biology Chapter 1 Reproduction in Angiospermic Plants
RBSE Class 12 Biology Chapter 1 Multiple Choice Objective Questions
Question 1.
Plant body in angiosperms is –
(a) Diploid sporophyte
(b) Haploid sporophyte
(c) Diploid gametophyte
(d) Haploid gametophyte
Answer:
(a) Diploid sporophyte
Question 2.
Plant part used for vegetative reproduction is called –
(a) Calyx
(b) Corolla
(c) Gynoecium
(d) Propagule
Answer:
(d) Propagule
Question 3.
Vegetative Propagation by tuber occurs in –
(a) Murraya
(b) Potato
(c) Bryophylluni
(d) Onion
Answer:
(b) Potato
Question 4.
Artificial vegetative propagation is done by Cutting in?
(a) Sugarcane
(b) Jasmine
(c) Mogra
(d) All the above
Answer:
(d) All the above
Question 5.
A flower is modified –
(a) Root
(b) Shoot
(c) Leaves
(d) Root tip
Answer:
(b) Shoot
RBSE Class 12 Biology Chapter 1 Very Short Answer Questions
Question 1.
Explain different parts or whorls of a flower.
Answer:
In a typical flower, there are four whorls, namely calyx, corolla, androecium and gynoecium. Calyx and corolla form accessory whorls and androecium and gynoecium are called necessary whorls.
Question 2.
What is Vegetative propagation/Reproduction?
Answer:
Formation of a new individual from any vegetative part of the plant body is called vegetative propagation. Many plants produce a modified structure on their vegetative parts which when separated from the mother plant, established as an independent plant. Such a method of
multiplication is called vegetative reproduction.
Question 3.
How does vegetative propagation is done in rose and mogra?
Answer:
In rose, vegetative propagation is carried out by stem cutting and in jasmine vegetative propagation is done by mound layering method.
Question 4.
Explain clearly about Cutting, Grafting and Layering techniques.
Answer:
- Cutting:
In this method, stem cuttings are used to obtain new plants. In order to promote rooting these are treated with IAA. - Grafting:
In this method, a branch of the plant having desired features are inserted in a rooted plant called stock. The branch which is inserted is called scion. This is practised to produce a new variety. - Layering:
In this method, roots are induced on the stem while it is still attached to the parent plant. This part is then separated from the parent plant and grown as an independent plant.
Question 5.
Differentiate between sexual reproduction and asexual reproduction.
Answer:
In angiosperms sexual reproduction necessarily involves meiosis and fertilization, ultimately resulting in seed formation. Whereas a method of formation of a new plant without involving meiosis and fertilization is called asexual reproduction. In asexual reproduction, only mitotic divisions are involved and hence the offsprings are genetically similar to the parent plant. In sexual reproduction, meiotic division results in variations and hence the offsprings show genetic variations.
Question 6.
Giving at least one example of each, list the type of stems modified for vegetative propagation.
Answer:
Question 7.
Explain vegetative propagation by leaves.
Answer:
Normally leaves do not help in vegetative propagation. However, in Bryophyllum pinnatum, adventitious buds develop along the leaf margins. These develop into small plantlets and on detachment develop into independent plants.
Question 8.
Differentiate between ‘stock’ and ‘scion’.
Answer:
During the practice of grafting the branch of a plant having desirable features is inserted into a rooted plant of the same or allied species. The branch which is inserted is called scion and the rooted plants in which the branch is inserted and which provides the supply of water and minerals is called stock.
RBSE Class 12 Biology Chapter 1 Short Answer Questions
Question 1.
What is Agamospermy?
Answer:
Agamospermy is a form of asexual reproduction in angiosperms in which seeds are formed without involving a fusion of gametes. The embryo present in the seed is not formed from a diploid zygote but is formed from a diploid egg.
Question 2.
Explain various methods of grafting.
Answer:
Grafting is a common practice in horticulture. In these two different plants are joined together so as to establish an organic union between the two.
The methods of grafting are –
- Whip or Tongue grafting
- Wedge grafting
- Crown grafting
- Bud grafting
1. Whip or Tongue grafting:
In this method both scion and stock are of similar thickness 5 -8 cm long cut is made in both scion and stock as shown in the diagram. After that, a V-shaped incision is made in the stock and a complimentary incision is made in the scion. The two are tightly fixed and covered with grafting wax.
2. Wedge grafting:
This method is adopted when the diameter of both scion and stock is exactly the same. The V-shaped incision is made in the stock whereas wedge-shaped incision is made in the scion. The two are then joined together, tightly fixed and sealed with grafting
3. Crown grafting:
This method is applied in the case where the diameter or thickness of the stock is many times more than the scion. The bark of the stock is cut through from the surface downwards to a length of 12 to 15 cm. A small branch of same species is incised and this is inserted into the slit in the bark and tied firmly. The wound is covered with grafting wax.
4. Bud grafting:
In this method, a T-shaped incision is made in the bark of the stock and a bud from a selected plant is inserted into the T-shaped slot and bandaged properly. By this method, it is possible to grow several varieties of rose on one stock.
Question 3.
Explain in brief vegetative reproduction by stem.
Answer:
Many plants produce a modified stem, especially for presentation and multiplication. The modified stems such as tuber, rhizome, corm, bulb, runner and offset have nodes and internodes and the buds at the nodes sprout under favourable conditions so as to form new plants. Common examples are – Rhizome-ginger, Tuber-potato, Bulb-onion, Corm-Colocasia, Runner-grass and Offset-water hyacinth.
Question 4.
Write a note on advantages of vegetative propagation.
Answer:
- It is a cheaper, and convenient method of multiplication of plants.
- Several plants: Such as banana, grapes, roses, gladioli, Chrysanthemums do not form viable seeds. Thus vegetative propagation is the only method of multiplication and continuation of species in such plants.
- The greatest advantage is that all plants produced by vegetative propagation are genetically similar to the parent plant. A uniform population raised from a single parent is known as a clone.
RBSE Class 12 Biology Chapter 1 Essay Type Questions
Question 1.
Explain in detail Asexual reproduction in angiosperms.
Answer:
In angiosperms, the normal method of reproduction is by seed formation involving meiosis and fertilization. This kind of reproduction is referred to as sexual reproduction. In several instances, angiosperms plants manage to reproduce by methods which do not involve meiosis and fertilization. Such a method of reproduction is called asexual reproduction or apomixis. In this method of reproduction, all divisions are mitotic and hence the offsprings produced are genetically similar to the parent plant.
Asexual reproduction can be divided into two types on the basis of the plant part involved in carrying out multiplication:
(i) Agamospermy:
Where a seed formed without involving meiosis and fertilization serves as a propagule.
(ii)Vegetative propagation:
Where a vegetative part of the plant such as stem, root, leaf etc. serves as a propagule. Vegetative Propagation can be defined as the formation of new individuals from any vegetative part of the plant body. In this method of reproduction, a portion of the vegetative part of the plant is separated or gets detached from the mother plant and develops into a new and independent plant.
Several plant species produce modified structures especially for their multiplication and perpetuation in nature. At the same time, man has developed several methods for multiplication of economically useful plants by artificial vegetative propagation.
Thus vegetative reproduction of plants can be described under two separate headings –
(i) Natural vegetative Propagation:
Different plant parts become modified to take the function of vegetative propagation. Some of these are as follows:
1. Vegetative propagation by stems:
(a) Tuber:
It is a modified underground stem developed from stem tip. The “eyes” or buds present in the tuber grow into a new plant under favourable conditions. The potato (Solanum tuberosum) tuber is the most commonly used tuber.
(b) Rhizome:
“The underground horizontally growing stem” is rhizome. These have distinct nodes and internodes and axillary buds. Axillary buds grow to form aerial shoot which later separates to form a new plant.
The common example includes ginger (Zingiber).
(c) Corm:
It is a condensed form of rhizome which grows in a vertical direction. The axillary buds grow into new plants. The common example is taro (Colocasia).
(d) Bulb:
It has a very short and condensed stem and apical and axillary buds. Some of these grow to form an aerial shoot. An example is an onion (Allium).
(e) Runners:
These are subaerial creeping stems which produce adventive roots at nodes. These break up at places and each piece grows as an independent plant. An example is doob grass (Cynodon).
(f) Offset:
It is similar to the runner in being prostrate and has more or less thickened branch with a tuft of leaves at the apex. the common example is water hyacinth (Eichhornia) and water lettuce (Pistia).
2. Vegetative propagation by roots:
In a few cases, roots also become modified and help in vegetative propagation. Some common examples are sweet potato (Ipomoea batatas), Asparagus and Dahlia.
3. Vegetative propagation by leaves:
Generally, leaves do not help in vegetative propagation. However, in Bryophyllum pinnatum, buds develop along the leaf margins. These buds grow into plantlets which on detachment establish as independent plants.
4. vegetative propagation by reproductive parts:
In some plants, special multicellular structures, called bulbils develop on an inflorescence. These are transformed floral buds. When these are shed from the plant, they develop into new plants e.g. onion (Allium cepa) and American aloe (Agave).
(ii) Artificial vegetative propagation:
These methods are devised by human and used for propagation of economically important plants. Various parts developed by plants for their natural vegetative propagation have also been practised for artificial vegetative propagation.
This is commercially useful because the new individuals produced by this method maintain the desirable characters of the parent. A population of genetically identical plants obtained from an individual by vegetative propagation is called a clone.
Artificial methods of vegetative propagation include cuttings, grafting, layering and micropropagation.
(1) Cuttings:
- Stem cutting
- Root cutting
1. Stem-cuttings:
Many plants such as rose, sugarcane, garden croton, china rose, Duranta, Coleus, Bougainvillea etc. may be easily multiplied by stem cuttings. When cuttings from such plants are put into the soil, they strike roots at the base and develop buds. Some times roots are not easily produced in the cuttings, then these are treated with IAA which promotes rooting.
2. Root cuttings:
Sometimes root cuttings put in moist soil sprout forming roots and shoots as in lemon,
tamarind etc.
(2) Grafting:
- Tongue grafting
- Wedge grafting
- Crown grafting
- Bud grafting
Grafting:
This is a commonly practised method in horticulture. In this method, two different plants are joined to develop a new variety. In this process, a small branch of a plant is inserted into a rooted plant of the same or allied species so as to establish an organic union between the two. The branch which is inserted is known as the Scion or graft, and the plant in which the branch is inserted and which is rooted in the soil is known as the stock.
The scion grows, retaining all its qualities, while the stock which may be of inferior quality, supports the scion by supplying water and food material. This method is useful in commercial plants such as rose, mango, apple, pear, guava, Citrus etc.
Main methods are as follows:
1. Whip or Tongue grafting:
In this method both scion and stock are of similar thickness 5 -8 cm long cut is made in both scion and stock as shown in the diagram. After that, a V-shaped incision is made in the stock and a complimentary incision is made in the scion. The two are tightly fixed and covered with grafting wax.
2. Wedge grafting:
This method is adopted when the diameter of both scion and stock is exactly the same. The V-shaped incision is made in the stock whereas wedge-shaped incision is made in the scion. The two are then joined together, tightly fixed and sealed with grafting
3. Crown grafting:
This method is applied in the case where the diameter or thickness of the stock is many times more than the scion. The bark of the stock is cut through from the surface downwards to a length of 12 to 15 cm. A small branch of same species is incised and this is inserted into the slit in the bark and tied firmly. The wound is covered with grafting wax.
4. Bud grafting:
In this method, a T-shaped incision is made in the bark of the stock and a bud from a selected plant is inserted into the T-shaped slot and bandaged properly. By this method, it is possible to grow several varieties of rose on one stock.
(3) Layering:
- Mound layering
- Gootee
Layering:
In this method, roots are induced in the stem while it is still attached to the parent plant. Later on, this part is detached and grown as an independent plant.
There are two common types of layering:
1. Mound layering:
In this case, a branch near the ground is bent down, a ring of bark (2.5 – 5.0 cm) is removed and this portion is pushed in the soft moist soil. It is done in such a way that the tip of the branch remains above ground. In a few days or weeks, the covered part of a stem strikes adventitious roots. At this stage, the branch is cut off from the parent plant and grown separately. Common examples are jasmine, grape – wine, lemon, rose etc.
2. Air layering or Gootee:
This technique is employed in trees with thick branches and which can not be bent easily. During early rains, a healthy and woody branch is selected and is girdled (i.e. a ring of bark, 2.5 – 5 cm long is sliced off). The girdled part is covered with moist moss or cotton and then covered with polythene bag or jute piece. This covered part is known as Gootee. To keep the gootee wet, an earthen pot with a minute hole at the bottom may be hanging over the gootee as shown in the diagram. Roots develop, usually, within 1 – 3 months. It is then separated from the parent plant and planted in the soil.
(4) Micropropagation:
This is a modern technique, used for raising disease-free plants, homozygous diploids etc.
Question 2.
Describe different parts of the flower of angiosperm.
Answer:
The flower is a modified shoot of limited growth. The stalk of the flower is called pedicel. At the free end of the pedicel, the flat broad platform forms the thalamus. Four types of modified floral leaves are arranged in four definite whorls on the thalamus. These whorls are Calyx, Corolla, Androecium and Gynoecium. The calyx consists of sepals, corolla of petals, androecium of stamens and gynoecium of carpels.
The calyx and corolla only help in the act of reproduction and do not take part directly in the process hence these are called non-essential or accessory whorls. The androecium is the male whorl whereas gynoecium constitutes the female whorl. These are called essential whorls as they take part in the process of reproduction.
Question 3.
Write a brief account of artificial methods of vegetative reproduction.
Answer:
These methods are devised by human and are practised to propagate commercially useful ornamentals and fruit plants.
The main methods of artificial propagation are:
(1) Cuttings:
- Stem cutting
- Root cutting
1. Stem-cuttings:
Many plants such as rose, sugarcane, garden croton, china rose, Duranta, Coleus, Bougainvillea etc. may be easily multiplied by stem cuttings. When cuttings from such plants are put into the soil, they strike roots at the base and develop buds. Some times roots are not easily produced in the cuttings, then these are treated with IAA which promotes rooting.
2. Root cuttings:
Sometimes root cuttings put in moist soil sprout forming roots and shoots as in lemon,
tamarind etc.
(2) Grafting:
- Tongue grafting
- Wedge grafting
- Crown grafting
- Bud grafting
Grafting:
This is a commonly practised method in horticulture. In this method, two different plants are joined to develop a new variety. In this process, a small branch of a plant is inserted into a rooted plant of the same or allied species so as to establish an organic union between the two. The branch which is inserted is known as the Scion or graft, and the plant in which the branch is inserted and which is rooted in the soil is known as the stock.
The scion grows, retaining all its qualities, while the stock which may be of inferior quality, supports the scion by supplying water and food material. This method is useful in commercial plants such as rose, mango, apple, pear, guava, Citrus etc.
Main methods are as follows:
1. Whip or Tongue grafting:
In this method both scion and stock are of similar thickness 5 -8 cm long cut is made in both scion and stock as shown in the diagram. After that, a V-shaped incision is made in the stock and a complimentary incision is made in the scion. The two are tightly fixed and covered with grafting wax.
2. Wedge grafting:
This method is adopted when the diameter of both scion and stock is exactly the same. The V-shaped incision is made in the stock whereas wedge-shaped incision is made in the scion. The two are then joined together, tightly fixed and sealed with grafting
3. Crown grafting:
This method is applied in the case where the diameter or thickness of the stock is many times more than the scion. The bark of the stock is cut through from the surface downwards to a length of 12 to 15 cm. A small branch of same species is incised and this is inserted into the slit in the bark and tied firmly. The wound is covered with grafting wax.
4. Bud grafting:
In this method, a T-shaped incision is made in the bark of the stock and a bud from a selected plant is inserted into the T-shaped slot and bandaged properly. By this method, it is possible to grow several varieties of rose on one stock.
(3) Layering:
- Mound layering
- Gootee
Layering:
In this method, roots are induced in the stem while it is still attached to the parent plant. Later on, this part is detached and grown as an independent plant.
There are two common types of layering:
1. Mound layering:
In this case, a branch near the ground is bent down, a ring of bark (2.5 – 5.0 cm) is removed and this portion is pushed in the soft moist soil. It is done in such a way that the tip of the branch remains above ground. In a few days or weeks, the covered part of a stem strikes adventitious roots. At this stage, the branch is cut off from the parent plant and grown separately. Common examples are jasmine, grape – wine, lemon, rose etc.
2. Air layering or Gootee:
This technique is employed in trees with thick branches and which can not be bent easily. During early rains, a healthy and woody branch is selected and is girdled (i.e. a ring of bark, 2.5 – 5 cm long is sliced off). The girdled part is covered with moist moss or cotton and then covered with polythene bag or jute piece. This covered part is known as Gootee. To keep the gootee wet, an earthen pot with a minute hole at the bottom may be hanging over the gootee as shown in the diagram. Roots develop, usually, within 1 – 3 months. It is then separated from the parent plant and planted in the soil.
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