Reproduction in Plants

1. Reproduction: All living organisms produce individuals of

their own kind for the survival of the species this is called
reproduction.

2. Reproduction in plants are broadly grouped into two types :

(i) asexual reproduction

(ii) sexual reproduction

3. Asexual reproduction : In Asexual Reproduction, only one

parent is involved and there is no formation or fusion of male
and female sex cells (gamets).

4. Sexual reproduction : In sexual reproduction, two parents

are involved and their is formation and fusion of the male and
female gametes.

5. Asexual reproduction is of five types -

(i) Binary fission

(ii) Budding

(iii) Fragmentation

(iv) Spore Formation

(v) Vegetative Reproduction

6. (A)Binary fission : Binary means two and Fission means

splitting) in this method the nucleus splits or divides into two
and then cell splits across the middle forming two small
identical cells called the daughter cells.
Eg - lower organisms like bacteria reproduce asexually by the
method of binary fission.

6. (B) Multiple fission : In some organisms like chlorella and

chlamydomonas one cell divides into four daughter cells. This
process is called multiple fusion.

7. Budding : Here the parent cell produces and out growth

called a bud. The bud grows and then get detached (along
with its daughter nuclei) from the parent body to lead an
independent life.

Eg - This method is common in yeast.

8. Fragmentation : When an organism breaks down into several

fragments it is known as fragmentation. Each fragment
develops into an individual and is a clone of the original
organism.

Eg - In organism such as Spirogyra which are made up of long

ribbon-like filaments which breaks off into two or more parts
call fragments and each fragment then regrows into an
individual organism.

9. Spore formation: In this process many spores are housed in

sacks known as Sporangia. The plants produce hundreds of
spores and the spores sac burst and are dispersed into the air
where they are carried away by wind or insects and where by
they germinate and create a new plant under favourable
conditions.

Eg - Spore formation is common in fungi and plants like

mosses and ferns.

10. Vegetative reproduction: New plants can be produced by

certain parts of a plants such as the leaf, steam and root.
These vegetative parts which are capable of giving rise to new
plants are called propagules and the process is known as
vegetative propagation.

11. Vegetative propagation can be of two types -

(i) Natural Vegetative Propagation

(ii) Artificial Vegetative Propagation

12. Natural vegetative propagation can be of 3 types -

(i) Reproduction by stem

(ii) Reproduction by leaf

(iii) Reproduction by root

13. Reproduction by stem: Vegetative propagation occurs

through stems when new plants arise from the nodes. This is
where buds are formed, which grow into new
plants. Stems that grow horizontally on the ground are called
runners. As these runners grow, buds form at the nodes, which
later develop the roots and shoots, resulting in the formation
of a new plant.

Eg : (i) Ginger has nodes and internodes and the nodes carry
thin, dry, brown papery scaly leaves. Auxiliary buds grow out
from the nodes to produce new plants.

(ii) Potato beers vegetative buds called the eyes. New plants
grow from these buds within a few days. Potatoes kept in
humid warm months may grew out shoots. If placed in soil,
they form complete plants.

(iii) Onion bulb has a thick, short, stem in the form of a

condened disc. The disc bears flashy overlapping scaly leaves
for storing food material. The disc-like stem bears terminal
and auxiliary buds. The auxiliary birds grow into new green
aerial shoots under favourable environmental conditions.

14. Ginger, potato and onion are called modified stems

because they perform additional functions of food storage
and vegetative propagation.

15. Reproduction by Leaf : Leaves of some plants such as

Bryophyllum, produce buds in the notches in thrir margins.
When such leaves fall in moist soil, their buds in the margins
vegin to grow as young tiny plants.

Eg: Is a plant whose leaves produce adventitious buds in their

margin. The adventitious buds grow into new plants under
favourable conditions when the leaf with buds fall off from
the parent plant.

16. Reproduction by root : In this process, new plants grow out

of the modified roots called tubers. In fact, in some plant
species, roots develop adventitious buds. These buds grow
and form new plants/sprouts under the right conditions.

Eg: (i) Plants like sweet potato and asparagus develop

numerous large swollen fleshy roots. These roots contain a
large quantity of food inside them. Each such single root is
capable of giving rise to new plant.
(ii) Carrot, a taproot is a biennial plant. Its roots grow
vegetatively in the first year and store food. In the following
year its steam produces flowers and seeds which die by the
end of the second year. buds produced at the base of the old
stem just above the tab root are meant for vegetative
propagation.

(iii) Lawn grass has long inter nodes between successive

nodes creeping on the surface of the ground. From each node
roots are given out. The axiliary buds at the nodes produce
new shoots.

17. Advantages of vegetative reproduction are -

(i) Reproduction by visited Parts takes place in a shorter time

(ii) New plants thus produce spread very fast in a small area

(iii) It is a shorter method of propagation

(iv) All the good characters of the mother plant are retained
by the daughter plants.

18. Disadvantages of vegetative reproduction are -

(i) As all plants developed by vegetative reproduction are

genetically identical they are all likely to be affected
simultaneously if a disease spreads in the farm.

(ii) This personal of plants does not take place on its own.
Daughter plants so developed tend to remain nearby and are
restricted to a particular area leading to competition for
resources.

19. Artificial vegetative propagation are of four types -

(i) Cutting

(ii) Layering

(iii) Grafting

(iv) Micro-propagation

20. Cutting : In this method the stem is cut into small pieces
with each bearing an axiliary bud. The cut ends are planted in
moist soil and after a few days they strike roots, and grow into
new plants.

Eg : Sugarcane, Rose, china rose, lemon etc

21. Layering : In this method, plant propagation takes place by

growth of roots in a portion of the aerial stem, which remains
attached with the parent plant. After some time, it detaches
from the parent plant.

Eg : Mint, rose, jasmine etc

22. Grafting : Grafting is the act of placing a portion of one

plant (bud or scion) into or on a stem, root, or branch of
another (stock) in such a way that a union will be formed and
the partners will continue to grow. The plant receiving the bud
or the shoot is called the stock and the shoot fixed on it is
called the scion.

Eg : Rose, mango, guava etc

23. Micro- Propagation : In this method, a small piece of plant

tissue (explant) is cultured in a sterile medium where cells
grow and divide to form a cell mass called callus which later
develops into new plantlets. After 4-6 weeks, the plantlets are
transferred to the soil.

Eg : Gladiolus, Crysanthemum etc

24. Advantages of plant tissue culture -

(i) It provides rapid propagation of identical individuals. This

technique is very productive for superior varieties.

(ii) It is very useful in cases where seeds are dormant. The

embryo in these seeds can be cultured and microprapagated.

25. Disadvantages of plant tissue culture -

(i) It requires a lot of scientific expertise.

(ii) It cannot be applied to all cases.

(iii) It is not easily applicable in remote agricultural areas.

26. Sexual reproduction : Sexual reproduction of plants refers

to the fusion of gametes in order to produce offspring. Most
of the plants bear flowers which are borne on shoots and
serve as the reproductive parts of the plant. They bear male
and female reproductive cells which on fusion produce seeds.
These seeds germinate to produce new plants.

27. Stalk : The flower is attached to the shoot by means of a

stalk or pedicel. The tip of the stalk is enlarged and slightly
flattened from where the petals and other parts arise. This
flattened part of the stalk is called the thalamus.

28. The four whorls of the flower are -

(i) Calyx
(ii) Corolla

(iii) Androecium

(iv) Gymnoecium

29. Calyx : This is the outermost part of the flower forming a

whorl of tiny green leaf-like structures called sepals. Sepals
are the green, outermost part of the flower.

30. Corolla : Made up of petals, it forms the second inner

whorl arranged next to the sepals. Usually, petals are white or
coloured but rarely green. Petals are the large, fragrant and
brightly coloured parts of the flower.

31. Androecium (The male part) : It is the third whorl to the

petals, consisting of delicate, thread-like structures called the
stamens. Each stamen is formed of a long, narrow, thin
filament and a broad sac-like bilobed anther found at its tip.
Each anther contains four pollen sacs in which the pillen
grains develop. The pollen grains contain the male gametes.
Stamens are the male reproductive parts of the flower.

32. Gynoecium (The female part) : It consists of carpels, the

fourth innermost part of the flowrr. It is also called a pistil.
Carpels are the female reproductive parts of the flower. Each
carpel is formed of three parts -

(i) Stigma at the top

(ii) Style in the middle

(iii) Ovary at the base

33. Ovules : These are the small, rohnded bodies present

inside the ovary. Each ovule contain an egg cell which later
develops into a seed after successful fertilisation.

34. Flowers bearing both male and female parta are called
bisexual flowers, while those bearing only male (staminate) or
female parts (piatilate) are called unisexual flowers.

35. Characteristics of a flower are :

(i) It is the reproductive organ of the plant.

(ii) A flower contains the male parts (stamens) and the female
parts (carpels).

(iii) The pollen grains from the male part are transferred by air
or insects to the female part of the flower.

36. Pollination : It is the process in which the pollen grains

from the anthers are transferred to the stigma of a flower of
the same species.

37. Pollination is of two types -

(i) Self-pollination

(ii) Cross-pollination

38. Self-pollination : It occurs either within the same flower or

between two flowers on the same plant. Here the pollen
grains from the anthers may fall on the stigma of the same
flower ot the stigma of another flower on the same plant.

39. Cross-pollination : It occurs between two flowers on

different plants of the same species.

40. Pollination takes place through 3 agents :

(i) Insects
(ii) Wind

(iii) Water

41. Insect pollination : when insects help in pollination such a

transfer of pollen grains is called insect pollination.
Butterflies, bees and other insects visit flowers for nector
(honey). When an insect alights on a flower, the pollen grains
stick to its mouth parts, wings, legs etc. When this insect visits
another flower, the pollen grains from its body may fall of on
the stigma of thaf flower.

Eg : Marigold, Dahlia, Salvia etc.

42. Characteristics of insect pollinated flowers :

(i) These flowers are large with coloured petals, to attract

insects.

(ii) These are scented so that insects locate the flowers by

smell.

(iii) These contain nectar as food for insects.

(iv) These produce sticky pollen grains so that they may stick
to the body parts of the insect.

43. Wind pollination : When wind is the agent of cross

pollination, it is called wind pollination. Some plants like
maize, palm, pine etc. produce dry pollen grains in large
quantity. When these flowers mature, the pollen grains get
blown away by the wind. These pollen grains falls on the
stigma of a flower of the same type and pollination occurs.

44. Characteristics of wind pollinated flowers :

(i) They are usually small and are of dull colours.

(ii) They generally have long anthers protruding out of the

flowet so that pollen grains may get blown off easily.

(iii) They produce large quantity of pollen.

(iv) The pollen grains are light so they are easily catried away.

45. Water pollination : When water acts as an agent of cross

pollination, it is called water pollination. These are aquatic
plants whose male flowers are submerged in water, get
detached when mature and float on the surface of water.
When these floating male flowers happen to come in contact
with a female flower the pollen grains are transferred to its
stigma.

Eg : Vallisneria

* Lotus and Trapa (Singhara) are aquatic plants but their

flowers are exposed to air and are pollinated by insects.

46. Characteristics of water pollinated flowers :

(i) Flowers are small and light so that they can easily float on
water.

(ii) Male and female flowers are borne on seperate plants.

(iii) Pollen grains are produced in large numbers.

47. Fertilisation : Fertilization is the fusion of the male sex cells

with the female sex cells to produce a zygote.

48. Fertilisation process : Once the pollen grain reaches the

stigma, it grows a tube called the pollen tube. This tube
extends through the style and enters the ovule in the ovary.
The male gametes fuse with the female egg cell to form a
zygote. The fertilized ovule becomes a seed with the ovule's
covering becoming the seed coat. The ovary develops into a
fruit while remaining attached to the flower's stalk. The ovules
inside the ovary turn into seeds, while sepals and petals fall
off.

49.

50. Artificial pollination : Artificial pollination means transfer

of pollen grains to the stigma manually. Artificial pollination is
practised by plant breeders for developing new varieties. The
breeders select two different varieties lf a crop plant with
desired characteristics.