3. INTRODUCTION
Plant tissue culture is a technique developed by Gottileb Haber
landt, a German botanist in 1898 based on the concept that any component part
of plant (Organs, cells, tissues) can be grown ‘in vitro’ to form a complete plant.
Many observations made in the culturing of embryo, root tip, stem tip etc. using
different methods were unsuccessful till 1930. Later many improved culture
media were developed to enable tissue culture more effectively.
The technique of tissue culture underwent rapid progress after the
discovery of activity of auxins and cytokinins. Plant callus culture and
suspension culture using normal and modified culture media are the major
advancements in plant tissue culture. The widely cultivated transgenic plants
like Bt. Cotton and golden rice is the outcome of tissue culture experiments.
Plant tissue culture is based on the efficiency of cell or tissues to
develop in to a complete plant. Any part or tissue of a plant used for the
production of a whole plant is called an explant. Parts like bud, leaf, anther, root
or any tissue can be used as explants. The unique capacity of plants is termed
cellular totipotency, which is not exhibited by animal cells.
RE DIFFERENTIATION & DE DIFFERENTIATION
A plant part or tissue cultured in a nutrient medium will undergo a
series of changes to achieve meristematic state. This phenomenon of reversal of
mature cells to meristematic state leading to the formation of callus is called de
differentiation. Callus formed in this way is a mass of undifferentiated
meristematic cells.
4. The capability of the callus to develop in to shoot/root/embryoid. It
is called Re- differentiation. Re differentiation is a process of formation of
specialized tissues and organs leading to the development of a complete plant
from undifferentiated callus.
MICRO PROPOGATION
Micropropogation is the widely used method for the rapid
multiplication and maintenance of superior clones, multiplication of disease free
plants and multiplication of sexually derived sterile hybrids. It is commonly
done in plants using shoot tips or axillary buds. Many crop plants, forest plants
and other plants of interest are being propogated by this method.
SYNTHETIC SEEDS (ARTIFICAL SEEDS)
Transportation, storage and handling of tissue cultured material
pose problems. To overcome, this, the concept of synthetic seeds or artificial
seeds are developed. In this technique, somatic embryos are encapsulated in a
matrix (Eg: Sodium alginate) along with substance like mycorrhiza, insecticide,
nitrogen fixing organisms, fungicide, herbicides carbon source and growth
regulators. The synthetic seeds have advantages like increased storage capacity,
easiness in handling etc.
SOMACLONAL VARIATION
Callus produced from leaf explants or protoplast culture generally
produces considerable variations in plant lets. This type of variation or
morphological variants are called somaclonal variations. Sometimes, these
variations may have affect economically important traits. The usefulness of this
variability can be effectively utilized in plant breeding programme. Creation of
disease resistant strains of potato is good example.
5. TECHNIQUES OF PLANT TISSUE CULTURE
Plant tissue culture is performed by the production of useful
products or production of new plant lets. The ‘in vitro’ culture of plant tissue is
an elaborate process involving the use of appropriate culture media and the
entire process is to be under taken in a well equipped laboratory.
1. CULTURE VESSELS
The culture vessels employed for plant tissue students involves
Erylen mayer flask (conical Flask), petri plates and culture tubes. (25 x 150
mm)
2. CULTURE MEDIUM
The significant media employed for all purpose experiment like
Gamborg medium (B5 medium), Mucashige and skoog medium (MS Medium)
white medium (W medium) and Nitsch medium. Different types of culture
media are proposed for different plants and organ culture. The culture medium
is stopped with cotton plug or aluminium foil sheet. The pH of the medium is
adjusted to 5.8 the acidic range.
3. STERILIZATION
Sterilization is the method used to get rid of the microbes like
bacteria and fungi in the culture medium and plant tissues. Thus, it is significant
to sterilize the culture medium and plant tissues.
6. The culture medium could be sterilized through keeping it in an
autoclave and keeping the temperature of 1210 C for 15 minutes. The plant
tissue is to be surface sterilized.
4. INOCULATION
Transfer of explants (stem, root, leaf etc) on to a culture medium is
called inoculation. The inoculation is performed within aseptic condition for
that an apparatus called laminar air flow chamber is employed.
5. INCUBATION
The culture flasks are incubated by keeping in a constant
temperature for a considerable time. This process is called incubation. The
temperature is adjusted around 250C constantly.
6. INDUCTION OF CALLUS
Because of activity of auxins and cytokinins, the explant is induced
to create callus. The callus is an undifferentiated tissue’s unorganized mass. The
technique of callus formation is that auxin induces cell elongation and
cytokinins induces cell division as a outcome of which masses of cells are
created.
7. MORPHOGENESIS
Creation of new organs from the callus under the effect of auxin
and cytokinin is termed as morphogenesis.
8. HARDENING
Displaying the plant lets to the natural environment in a step wise
way in termed as hardening. At last the plantlets are gradually transferred to the
soil.
9. Various commercial establishments now routinely use micro propogation
for dissimilar foliage and ornamental plants.
By tissue culture methods by using bud poliferation and multiple shoot
formation, ornamental plants are generated in large numbers.
Virus free germplasm are generated by apical meristem culture for
example banana.
Artificial synthetic seeds are generated by somatic embryogenesis.
Plant tissue culture is a significant method for the production of
secondary metabolites in large quantities.
Embryo culture method is applied to overcome embryo abortion, seed
dormancy and self sterility in seeds.
In current years, plant tissue culture methods are used in plants for the
introduction of foreign gene in to plant cells by DNA coated micro
particles and delivering these particles in to a host cell through using a
gene gun.
Protoplasmic fusion encourages genomes of incompatible crops to come
together to create somatic hybrids.
Through plant tissue culture techniques, a plant cell of potato and tomato
were brought together by protoplasmic fusion and the hybrid cell was
created to develop in to a pomato plant. In pomato, the stem bears the
tubers and the branches generated tomatoes.
10. CONCLUSION
Tissue culture is the growth of tissues or cells separate from the
organism. This is typically facilitated via use of a liquid, semi solid growth
medium, such as broth or agar. Tissue culture commonly refers to the culture of
animal cells and tissues, with the more specific term plant tissue culture being
used for plants.
11. REFERENCES
K. Vijayakumaran Nair,
M. Jayaprakash
S. Sreekumar
Cell biology, genetics, Biotechnology, Plant breeding, 2004.
https://en.m.wikipedia.org
