This document provides an overview of plant tissue culture techniques. It defines plant tissue culture as growing plant cells, organs or tissues in a sterile environment with nutrient media. The key requirements for plant tissue culture are appropriate explant tissue, a suitable growth medium, aseptic conditions, growth regulators, and frequent sub-culturing. Plant tissue culture has advantages over working with intact plants like enabling large-scale growth and genetic modification. The document discusses regeneration methods like shoot regeneration and somatic embryogenesis that allow developing whole plants from cultured cells or tissues. It also covers the stages of micropropagation including multiplication, rooting, and acclimatization of plantlets.
4. Definitions:
• “Tissue culture” widely for in vitro culture of cells, tissues as well
as organs
• Plant Tissue Culture is a technique of growing plant cells, organs,
seeds or other plant parts in a sterile environment on nutrient
medium.
5. Basics of Plant tissue culture
• In vitro cultivation primarily to solve two basic problems:
1. To keep plants and organs free from microbes
2. To ensure desirable development in cells and organs by providing
suitable nutrient media & other env. conditions.
Area of active research
6. What conditions do plant cells
need to multiply in vitro?
Tissue culture has several critical requirements:
Appropriate tissue
A suitable growth medium
Aseptic (sterile) conditions
Growth regulators
Frequent sub-culturing
7. Appropriate tissue (Explant)
• Explants: Cell, tissue or organ of a plant that is used to start in vitro
cultures.
• Most commonly: axillary buds and meristems
• The explants must be sterilized to remove microbial contaminants
Chemical Conc. Duration (min)
Bromine water 1-2 % 5-10
Calcium hypochlorite About 10% 5-30
Hydrogen peroxide 10-12 % 10-15
Mercuric chloride 0.1-1.0 % 5-15
Sodium hypochlorite 2 % 5-30
Antibiotics 4-50 mg/L 30-60
8. Growth medium
• A nutrient medium is defined by its mineral salt composition, carbon
source, vitamins, plant growth regulators and other organic
supplements.
Composition:
Inorganic nutrients
Vitamins
Carbon source
Growth Regulators
Complex organic additives
12. Flow chart of plant propagation by:
tissue culture method
13. Advantages of tissue culture OVER
intact plants
1. Can grow plant cells in liquid culture on a large scale—Bioreactor
2. Dihaploid plants production from haploid cultures shortens the time
taken to achieve uniform homozygous lines
3. The crossing of distantly related species by protoplast isolation and
somatic fusion help in transfer and expression of novel genes
4. Cell selection increases the potential number of individuals in a
screening program
5. Micropropagation allows the production of large numbers of uniform
individuals of species from limited starting material
6. Genetic transformation of cells enables very specific information to be
introduced into single cells which can then be regenerated
15. Plant regeneration
• The process of growing an entire
plant from a single cell or group of
cells
• Possible because plant cells can be
made totipotent using hormones
• Differentiated tissue: stem, leaves,
roots etc.
• Undifferentiated cells are
totipotent: can become whole plant
by differentiating into whole plant
17. Plant Regeneration System
Plant regeneration
Organogenesis--Shoots or roots are
induced to differentiate from a cell or cell
clusters (Shoot regeneration will be
discussed)
Somatic embryogenesis--New plants are
formed from somatic embryos. Somatic
embryos are formed in plant tissue culture
from plant cells that are not normally
involved in the development of embryos, i.e.
ordinary plant tissue
18. Shoot Regeneration
• First report by :White in 1939 in tobacco tissue culture
• Shoot buds usually arise from group of meristematic cells called
meristemoids/nodules
• Meristemoids leaf primordia and apical meristem
• Arise in areas that accumulate starch
• GA3 inhibit shoot regeneration by interfering with starch
accumulation
19. Shoot induction
Shoot differentiation
and development
Events during shoot regeneration
Morphogenic competence
acquisition Phase
Developmental
determination phase
Commitment
is
irreversible
21. Somatic Embryogenesis
• Somatic embryo is an embryo derived from a somatic cell,
other than zygote.
• Somatic embryogenesis is defined as the process of
development of a bipolar structure like zygotic embryo from
a non-zygotic somatic cell
• Doesn’t have vascular connections
• Reported in 1968 independently by Steward and Reinert in
carrot
22. Developmental pattern of SEs
Direct SE regeneration is most likely to occur from ovules, zygotic embryos and young seedlings
24. Gene Gene product Function
CHB-2 Homoeoprotein Vascular element diff.
EP2 Lipid transfer protein (LTP) Acquisition of
embryogenic potential
AlLTP1 LTP Protoderm formation
EP3 Extracellular endochitinase Protoderm formation
TS11 Arabinogalactan proteins
(AGPs)
Globularheart
shaped
Some of the Genes involved in
SE..
25. S.N Characteristic Shoot Bud Somatic Embryo
1 Origin Many cells Single cell
2 Polarity Unipolar Bipolar
3 Vascular connection with
callus/explant
Present Absent
4 Separation from callus/explant Not easily
separated unless
cut off
Easily separated
as radicular end
is cutinized
Comparison between shoot bud &
SE
27. Introduction
• Micropropagation is the process of rapidly multiplying stock plant
material to produce large number of progeny plants using plant tissue
culture methods
• Achieved by following processes:
Proliferation of axillary buds
Induction of adventitious buds
Organogenesis
Somatic Embryogenesis
• For axillary bud proliferation: Pre-existing meristem cultured
28. • SAM is the portion lying distal to youngest leaf primordium (100 μm
dia and 250 μm in length)
• Shoot tip apical meristem + 1-3 young leaf primordia (=500 μm)
• If objective is rapid propagation size is not important
• If objective is virus free minimum surrounding tissue
Meristem culture
29. Meristem culture
• Shoot tips of 0.5 mm or longer grow into shoots on GR-free media
(low levels of auxin/or cytokinin is preferred)
• Without leaf primordia culture auxin is essential in most cases
and cytokinin in some cases (as meristematic dome doesn’t produce
its own auxin and cytokinins)
2,4-D
avoided
GA3 is
often used
Leaf primordia
provides app.
amount of auxin
and cytokinin
30. 0
• Selection and preparation of mother
plants
1 • Culture initiation
2 • Multiplication
3 • Rooting of shoots
4 • Transfer to soil
Stages of Micropropagation
31. • Identification and preparation of mother plants more responsive
explants
• Stock plants under controlled conditions (glass house)good
• Overhead irrigation should be avoided
• Reduce level of contamination
• To increase responsiveness light, temp, GR
• “Rejuvenation” in tree species
0-Preparation of mother plants
32. • Surface sterilization of explants and establishing them in vitro
• Main feature detection and elimination/control of contamination
• GR-free medium used
• In case of contamination antibiotic or fungicide may be added
• Most commonly used explants are organs, shoot tips, nodal segments.
1-Culture initiation
33. • Most crucial stage as it determines the rate at which plantlets are
formed
• Multiplication by:
Enhanced proliferation of axillary shoot buds
Induction of adventitious buds, bulbs, etc.
Somatic embryogenesis (SE)
• Defined culture medium
2-Multiplication
34. • GR-free/ auxin stimulation
• On agar medium in vitro rooting
• Directly on potting mix after treating ends with auxin solution ex
vitro/ in vivo rooting
3-Rooting of shoots
Rooting and soil
transfer stages are
combined
Structurally and functionally
better roots
Better rooting to difficult
root species
No risk of root damage during
transfer to soil
Saving of labour and media
reagents
35. 4-Transfer to soil
Rooted shoots
are removed
from medium
Agar sticking
to roots
washed with
tap water
Transplanted
into plastic
cups
↓
High Humidity:
Fog
Mist
Clear cups
37. 1. Modified nutrient media and culture condition
2. Chemical additives in culture media
3. Co-culture with microorganisms
. . . Hardening/Acclimatization
...1
↑ aeration
↑ light intensity
↑ CO2 level
↓ Sucrose level
Favour photoautotrophy
...2
Polyethylene glycol
Paclobutrazol
Cuticular Biosynthesis
...3
Bacterization with
Pseudomonas
Root Colonization
with endomycorrhia
↑ Lignin content,
↑ stomatal function,
↑ tolerance to dehydration
38. Choice of Route for
Micropropagation
When all three (axillary, adv,
SE) are available Axillary is
preferable
Chimeras (two genetically
different tissues) Axillary
Desirable feature due to virus
as in geranium “crocodile”
variety adv shoot bud
regeneration
Easier, faster and more
practicable route of
micropropagation
Golden netting in
the leaf veins of
Geranium
Bulblet
regeneration
from bulb scale
in lilies
Editor's Notes
Area of active research: relies mainly on the manipulation of culture medium especially GR and to much lesser extent on other factors
Tissue culture has several critical requirements:
Appropriate tissue
A suitable growth medium containing energy sources and inorganic salts to supply cell growth needs. This can be liquid or semisolid.
Aseptic (sterile) conditions, as microorganisms grow much more quickly than plant and animal tissue and can overrun a culture.
Growth regulators - in plants, both auxins & cytokinins.
Frequent subculturing to ensure adequate nutrition and to avoid the build-up of waste metabolites
This is usually done by chemical surface sterilization with an agent for a duration that will kill pathogens w/o injuring the plant cells
When an explant is isolated, it is no longer able to receive
nutrients or hormones from the plant, and these must be
provided to allow growth in vitro. The composition of the
nutrient medium is for the most part similar, although the
exact components and quantities will vary for different
species and purpose of culture. Types and amounts of
hormones vary greatly. In addition, the culture must be
provided with the ability to excrete the waste products of
cell metabolism. This is accomplished by culturing on or in
a defined culture medium which is periodically
replenished.
N in the form of amino acids (glutamine, asparagine)
and nucleotides (adenine)
- Organic acids: TCA cycle acids (citrate, malate,
succinate, fumarate), pyruvate
- Complex substances: yeast extract, malt extract,
coconut milk, protein hydrolysate
- Activated charcoal is used where phenol-like
compounds are a problem, absorbing toxic pigments
and stabilizing pH. Also, to prevent oxidation of
phenols PVP (polyvinylpyrrolidone), citric acid,
ascorbic acid, thiourea and L-cysteine are used.
protoderm. a thin outer layer of the meristem in embryos and growing points of roots and stems, which gives rise to the epidermis.
Shoot apical meristems produce one or more axillary or lateral buds at each node. When stems produce considerable secondary growth, the axillary buds may be destroyed. Adventitious buds may then develop on stems with secondary growth.