Reproduction in plants

Reproduction in plants
Jegatheeswari karthik

Reproduction
The process of producing young
ones of same kind .
It is needed for the survival of the
species.

Modes of reproduction
1. Asexual reproduction
● Only one parent is involved
● No formation of gametes or sex cells
2. Sexual reproduction
● Two parents are involved
● Involves formation of gametes

Asexual reproduction
Asexual reproduction takes place by
the following methods.
1. Binary fission
2. Budding
3. Fragmentation
4. Spore formation
5. Vegetative reproduction

Binary fission
Binary means two
Fission means splitting
One cell divides or splits to form two
daughter cells.

Binary fission steps
1. Nucleus divides into two
2. The cell splits into two across the
middle
3. Example ; Bacteria and Amoeba

Multiple fission
One cell divide into more cells
Example; Chlorella and
Chlamydomonas

Budding
● Parent cell produces an outgrowth
called buds.
● Bud grows long.
● Once if it attains full growth it will get
detached from the parent.
● Example; Yeast

Fragmentation
● Takes place in multicellular
organisms
● is a form of asexual reproduction in
which an organism is split into
fragments.
● Each of these fragments develop into
matured, full grown individuals that
are identical to their parents.

Spore formation
● Common in plants like mosses and
ferns
● Bear spores on the underside of their
leaves.
● Spores are light and can be carried
away by wind or by insects.
● On suitable conditions, spores give
rise to new plants.

Vegetative reproduction
or vegetative propagation
● New plants will be produced by
certain vegetative parts.
● The vegetative parts of a plant
that are capable of giving rise to
new plants are called propagules.

Natural vegetative
propagation
1. Reproduction by stem
2. Reproduction by leaves
3. Reproduction by root

Reproduction by stem
● Ginger, Potato and onion
● These are called modified stems.
● Because they perform additional
functions of food storage and
vegetative propagation.

Propagation by stem
● Node - Nodes are the points on
a stem where the buds, leaves, and
branching twigs originate.
● Internode – The distance between
the two nodes.

Propagation by stem ● Auxiliary bud- The axillary
bud (or lateral bud) is an embryonic
shoot located in the axil of a leaf.

Rhizome of Ginger ● Rhizome of Ginger is a type of underground
modification of stem which grows horizontally
underground and bear nodes, internodes
and scaly leaves and buds, which gives rise
to aerial shoots. ...

To grow ginger by vegetative
propagation
1. Take healthy piece of ginger
2. Cut one small piece and place it in moist
soil in flower pot
3. Keep it for 8-10 days.
4. Daily sprinkle the water.
5. Auxiliary buds grow into aerial shoots to
form new plant.

Propagation of
Potato Tuber
Potato bears vegetative buds
Called eyes.

To grow potato by vegetative
propagation
1. Take healthy piece of potato having eyes
2. Put this potato in moist soil. Cover only
one layer of soil.
5. Each leafy buds grow to form new plant.

Propagation of
Onion Bulb
Onion bulb has a thick, short, stem
in the form of a condensed disc.

Onion bulb
● Onion bulb has a thick, short, stem in the
Form of a condensed disc.
● The disc bears overlapping scaly leaves
for storing food material.
● The disc like stem bears terminal and
axillary buds.
● Under favourable conditions auxillary buds
grow into new plant.

To grow onion bulb by
vegetative propagation
1. Take healthy piece of onion bulb.
2. Place it in moist soil.
5. Auxiliary buds grow into aerial shoots to
form new plant.

Reproduction by leaf
● Bryophyllum
● Produces buds in the notches in their
margins.
● The adventitious buds grow into new
plants under favourable conditions when
the leaf buds falls off from the parent
plant.

Propagation by Root
● Sweet potato and Asparagus develop
numerous large swollen fleshy roots.
● Contain a large quantity of food inside them.
● Each single root is capable of giving rise to new
plant.

To grow grass by
vegetative reproduction
● Put a small piece of lawn grass in a pot
● Cover some of the portions with moist soil.
● 10-12 days
● Sprinkle water everyday.
● After few days new grass shoots grow out
from the buds

Advantages of vegetative
propagation
● Shorter time
● New plants spread very fast in a small
area.
● 100% result
● All the good characters of the mother
plant are retained by the daughter
plants.

Disadvantages of
vegetative propagation
• Vegetative propagation includes overcrowding.
• There is no genetic variation and plants are less
adaptable to environment.
• The diseases of parent plants are transferred to
off springs.
• No variations.
• plants can be easily decayed.
● .

Artificial vegetative
propagation
1. Cutting
2. Layering
3. Grafting
4. Micro- Propagation

Grafting
• Grafting is a technique that vegetatively
joins two plants into one.
• Grafted plants use the roots and the
bottom portion of one plant and attach it to
a tender shoot from the top portion of
another plant.

Things to know in
grafting
● Stock – The plant receiving the bud
or the shoot is called stock
● Scion - The shoot fixed on it is called
scion
● Cambium layers of the stock and
scion must come in close contact for
successful graft.

Grafting importance
● In modern horticulture, grafting is used
for a variety of purposes
● To repair injured trees,
● To produce dwarf trees and shrubs,
● To strengthen plants' resistance to
certain diseases,
● To adapt varieties to adverse soil or
climatic conditions,
● To ensure pollination,

The grafted points are
bound together with tape
and the joint is covered
with wax. Why?
● To prevent dehydration
● To protect from bacterial
infection.
● Rose , Mango and Guava

Micro-propagation
● Micropropagation is the practice of
rapidly multiplying stock plant
material to produce many progeny
plants, using modern plant tissue
culture methods.

Micropropagation
● Micropropagation differs from all other
conventional propagation methods in that
aseptic conditions are essential to achieve
success. The process of micropropagation can
be divided into four stages:
1. Initiation stage
2. Multiplication stage
3. Rooting or pre planting stage
4. Acclimatization

Procedure
● Tissue of vegetative buds , shoot
apex as an ex-plant.
● Explants are treated with sterilization
chemicals. ( to prevent microbial
growth)
● Cultured in nutrient medium
● Cells grow and divide to form a mass
called callus.

Procedure
● Some growth regulators are added
● Callus differentiates in to plant parts
called plantlet.
● 4-6 weeks plantlets are transferred to
the soil.
● For getting disease free plants it is
used.
● Orchids, Gladiolus, Chrysanthemum

Benefits
● Rapid propagation of identical
individuals
● Useful in case of dormant seeds.
The embryo in these seeds can be
cultured and micro propagated.

Limitations of tissue
culture
● Lot of scientific expertise is
required.
● Not applicable to all plants
● Not applicable in remote areas.

Sexual reproduction
● Two parents are involved
● Formation of gametes
● Fusion of male and female gametes
are involved.
● Flowers are the reproductive parts of
the plant.

Parts of a flower
● There are three main parts of a flower. They
are
● Stalk
● Thalamus
● Four whorls. The four whorls include
1. Calyx
2. Corolla
3. Androecium
4. Gynoecium

Parts of a flower
● Stalk – The flower is attached to the
shoot by means of stalk or pedicel.
● Thalamus- The tip of the stalk is
enlarged and slightly flattened from
where the petals and the other
parts arise.

Whorls of the flower
● Calyx
● Outermost whorl
● Made up of group of sepals(Green)
● In the bud stage, they enclose the
inner parts of the flower and provide
protection.

● Corolla
● Second whorl inner to sepals.
● Made up of group of petals
● Petals or white or coloured.
● It make the flower attractive
● They are large, fragrant and
brightly coloured parts of the
flower

● Androecium – Male part
● Third whorl inner to the petals.
● Made up of group of stamens.
● Stamen is a thread-like structure.
● It is made up of Anther and Filament.
● Each anther contains four pollen sacs.
● Pollen sacs contain pollen grains and
these produce male gamete.

● Gynoecium – Female part
● Last whorl inner to the stamens.
● Made up of carpel. ( Pistil).
● It is made up of ovary, Style and Stigma.
● Ovules are the round structures present
inside the ovary.
● Each ovule contains egg or the female
gamete

Unisexual and bisexual
flowers
● Stamens are the male reproductive parts of
the flower.
● Carpels are the female reproductive parts
of the flower.
● Flowers bearing both male and female
parts are called bisexual flowers.
● The flowers that contains only male or
female parts are called unisexual flowers.

Examples of unisexual
flowers
● Coconut flowers, Papaya, Watermelon,
Cucumber, Maize, White mulberry, Musk
melon Coconut flowers, Papaya,
Watermelon, Cucumber, Maize, White
mulberry, Musk melon

Functions of a flower
● Helps for reproduction

Pollination
● Is the process in which the pollen
grains from the anthers are
transferred to the stigma of a
flower of the same species

Types of pollination
1. Self- pollination is one that occurs either
within the same flower or between two
flowers on the same plant.
2. Cross – pollination is one that occurs
between two flowers on different plants
of the same species.

Agents of cross
pollination
1. Insects
2. Wind
3. Water

Insect pollination
Marigold, Dahlia

Characteristics of insect
pollinated flowers
● Large with coloured petals,
● Scented
● Nectar
● Produce sticky pollen grains
● Birds , Squirrels, Bats
● Even Elephant

Rafflesia arnoldii
● Pollination will be done by Elephants

Wind pollination
 Maize , palm, pine produce dry
pollen grains in large quantity.
 When these flowers mature, the
pollen grains get blown by the wind.
 Most of them are wasted.

Characteristics of wind
pollinated flowers
● Small and of dull colours.
● Long anthers protruding out of the
flower so that pollen grains may get
blown off easily.
● Large quantity of pollen
● Very light

Water pollination
● Vallisneria – Aquatic plant
● Male flowers submerged in water
● When mature, get detached
● And float on surface of water.
● Come in contact with female flower

Characteristics of water
pollinated flowers
● Small and light
● Unisexual flowers
● Pollen grains are produced on large
numbers

Fertilisation
● Fusion of male and female sex cells
or gametes.
● Zygote formation

Flow chart of fertilisation
● Pollination
● Germination of pollen tube
● Penetration of the ovule
● Double fertilisation

Pollen tube entering the
ovule

Pollination , Germination
of pollen tube
● Pollen grains from anther lands
on the surface of stigma.
● Upon absorbing moisture, the
pollen grain begins to form a
pollen tube
● Pollen tube lengthens towards
egg cell.

Penetration of the ovule
● Pollen tube penetrates the
female gametophyte and
enter into the ovule.
● Fusion of male and female
nuclei takes place.

Fruit developement
● Ovary will turn in to Fruit
● Ovule will become Seed
● Covering of ovule will become
seed coat
● Zygote will become a Embryo
● Other parts like, sepals and petals
fall off.

Artificial pollination
● The breeders select two
different varieties of a crop
plant with desired
characteristics.
● High yielding
● Disease resistant
● Ex. Rice , Wheat and Maize

Reproduction in plants

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