2. INDEX
1.Definitions
>Plant cell and tissue culture
>Totipotency
>Competency
>Organogenesis
>Embryogenesis
2.Basis for Plant Tissue Culture
> Factors Affecting Plant Tissue Culture
3.Micropropagation
> Steps of Micropropagation
4.Somaclonal Variation
>Inducing Mutations
3. Definitions
โข Plant cell and tissue culture: cultural
techniques for regeneration of functional plants
from embryonic tissues, tissue fragments, calli,
isolated cells, or protoplasts
โข Totipotency: the ability of undifferentiated plant
tissues to differentiate into functional plants
when cultured in vitro
โข Competency: the endogenous potential of a
given cell or tissue to develop in a particular way
โข Organogenesis: The process of initiation
and development of a structure that shows
natural organ form and/or function.
โข Embryogenesis: The process of initiation
and development of embryos or embryolike
structures from somatic cells (Somatic
embryogenesis).
Basis for Plant Tissue Culture
4. โข Two Hormones Affect Plant Differentiation:
โ Auxin: Stimulates Root Development
โ Cytokinin: Stimulates Shoot Development
โข Generally, the ratio of these two hormones
can determine plant development:
โ โ Auxin โCytokinin = Root Development
โ โ Cytokinin โAuxin = Shoot Development
โ Auxin = Cytokinin = Callus Development
Factors Affecting Plant Tissue Culture
โข Growth Media
โ Minerals, Growth factors, Carbon source, Hormones
โข Environmental Factors
โ Light, Temperature, Photoperiod, Sterility, Media
โข Explant Source
โ Usually, the younger, less differentiated the explant,
the better for tissue culture
โข Genetics
โ Different species show differences in amenability to
tissue culture
โ In many cases, different genotypes within a species
will have variable responses to tissue culture;
response to somatic embryogenesis has been
transferred between melon cultivars through sexual
5. hybridization
Micropropagation
โข The art and science of plant multiplication
in vitro
โข Usually derived from meristems (or
vegetative buds) without a callus stage
โ Tends to reduce or eliminate somaclonal
variation, resulting in true clones
โข Can be derived from other explant or
callus (but these are often problematic)
Steps of Micropropagation
โข Stage 0 โ Selection & preparation of the mother plant
โ sterilization of the plant tissue takes place
โข Stage I - Initiation of culture
โ explant placed into growth media
โข Stage II - Multiplication
โ explant transferred to shoot media; shoots can be
constantly
divided
โข Stage III - Rooting
โ explant transferred to root media
โข Stage IV - Transfer to soil
โ explant returned to soil; hardened off
6. Somaclonal Variation
โข The source for most breeding material
begins with mutations, whether the
mutation occurs in a modern cultivar, a
landrace, a plant accession, a wild related
species, or in an unrelated organism
โข Total sources of variation:
โ Mutation, Hybridization, Polyploidy
Inducing Mutations
โข Physical Mutagens (irradiation)
โ Neutrons, Alpha rays
โข Densely ionizing (โCannon ballsโ), mostly chromosome
aberrations
โ Gamma, Beta, X-rays
โข Sparsely ionizing (โBulletsโ), chromosome aberrations & point
mutations
โ UV radiation
โข Non-ionizing, cause point mutations (if any), low penetrating
โข Chemical Mutagens (carcinogens)
โ Many different chemicals
โข Most are highly toxic, usually result in point mutations
โข Callus Growth in Tissue Culture