Micropropagation and Its Applications
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Direct answer
One shoot tip, sterilised and fed on a nutrient medium with the right auxin-to-cytokinin ratio, can yield thousands of genetically identical plants in a year — that industrial arithmetic is micropropagation, the tissue-culture route to multiplying plants from an explant. The technique rests on totipotency, the capacity of a living plant cell to regenerate an entire organism, and it delivers what fields cannot: round-the-year multiplication, disease-free stock through meristem culture, rescue of rare and endangered species, and rapid bulking of elite hybrids. Its deliberate by-product, somaclonal variation, supplies new variants for selection, while protoplast fusion extends the same laboratory into somatic hybridisation between species that will not cross sexually.
What you must remember
- Vocabulary NCERT uses: explant (the excised piece used to start a culture), totipotency (the regenerative capacity of plant cells), callus (the unorganised mass that forms before organogenesis).
- Virus-free plants: culturing the shoot apical meristem yields virus-free stock because the dividing meristem typically carries no virus; banana, sugarcane and tomato are NCERT's named successes.
- Somaclonal variation: plants regenerated from cell culture show variation over the parent; NCERT lists it among methods for producing plants with novel characters — useful, not a defect.
- Somatic hybridisation: protoplasts (cells stripped of walls) of two species fused — tomato and potato gave the pomato, NCERT's example — though such hybrids are often not fertile or useful in practice.
- Multiplication of rare material: endangered species and elite hybrids multiply far faster in vitro than by seed, since each cycle takes weeks rather than seasons.
- Conditions of the craft: aseptic technique, a defined nutrient medium with sucrose, vitamins and growth regulators, and controlled light and temperature — "sterile" is the one-word answer to most setup questions.
- Scale: micropropagation is used commercially for orchids and ornamentals on NCERT's account, and India uses it for banana and sugarcane clean-plant programmes in practice.
Walk the sequence from explant to field
Everything begins with an explant — a shoot tip, a bud, a leaf disc — surface-sterilised and laid on medium. Cells at its cut edges dedifferentiate into a callus, and the growth-regulator balance then steers what happens next: a high cytokinin-to-auxin ratio pushes shoots; a high auxin ratio pushes roots; plantlets form and are hardened off, gradually acclimatised from humid culture jars to open air before going to soil. In rapid multiplication schemes, shoot clusters are cut and recultured every few weeks, so a single clone can fill a nursery within months. This is why a newly released hybrid reaches farmers in two or three years instead of a decade of seed increase.
The two applications with exam weight both bend this pipeline. Meristem culture takes just the dome of the apical meristem, a region without vascular connection to the rest of the plant and hence usually free of viruses, to found clean planting material. Somaclonal variation reads the same pipeline in the opposite direction: instead of identical clones, culture itself throws up variants — changes in chromosome number or gene expression — among which a breeder may select improved lines, a source of novelty NCERT explicitly credits.
Where students lose marks
The virus logic must be quoted correctly: meristem culture works because the meristematic region is generally free of the virus, not because the medium kills viruses — a statement question that reverses this collects the wrong half of the batch. Second, pomato: it is the product of somatic hybridisation (protoplast fusion) of tomato and potato, and it is of no practical use — NCERT says so plainly, and "produces tomato-potato on one plant commercially" is a planted error. Third, somaclonal variation is asked both as a benefit (novel variants) and as a departure from clonal uniformity; read which framing the stem wants before judging it a defect.
Frequently asked questions
What is micropropagation?
The production of large numbers of plants from a small explant grown in sterile nutrient culture, exploiting the totipotency of plant cells.
How are virus-free plants obtained through tissue culture?
By culturing the shoot apical meristem, which is generally free of viruses, as in NCERT's examples of banana, sugarcane and tomato.
What is somaclonal variation?
Genetic variation appearing among plants regenerated from cell cultures, a source of novel characteristics for selection.
What is somatic hybridisation, and what is NCERT's example?
Fusion of naked protoplasts of two different species, illustrated by the pomato from tomato and potato protoplasts, though it has no practical use.
Why can micropropagation help conserve endangered species?
It multiplies rare plants rapidly from minimal starting material under controlled conditions, bypassing the slow seed-to-seed cycle.