Micropropagation facts for kids

A rose plant that began as cells grown in a tissue culture

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

Micropropagation is used to multiply a wide variety of plants, such as those that have been genetically modified or bred through conventional plant breeding methods. It is also used to provide a sufficient number of plantlets for planting from seedless plants, plants that do not respond well to vegetative reproduction or where micropropagation is the cheaper means of propagating (e.g. Orchids). Cornell University botanist Frederick Campion Steward discovered and pioneered micropropagation and plant tissue culture in the late 1950s and early 1960s.

Steps

In vitro culture of plants in a controlled, sterile environment

[[File:Banana plantlets transferred to soil (with vermicompost) from plant media.jpg|thumb|Banana plantlets transferred to soil (with vermicompost) from plant media. This process is done for acclimatization of [[File:Plant tissue cultures, National Center for Genetic Resources Preservation, USDA.jpg|thumb|Plant tissue cultures being grown at a USDA seed bank, the National Center for Genetic Resources Preservation]]

In short, steps of micropropagation can be divided into four stages:

1. Selection of mother plant
2. Multiplication
3. Rooting and acclimatizing
4. Transfer new plant to soil

Advantages

Micropropagation has a number of advantages over traditional plant propagation techniques:

• The main advantage of micropropagation is the production of many plants that are clones of each other.
• Micropropagation can be used to produce disease-free plants.
• It can have an extraordinarily high fecundity rate, producing thousands of propagules while conventional techniques might only produce a fraction of this number.
• It is the only viable method of regenerating genetically modified cells or cells after protoplast fusion.
• It is useful in multiplying plants which produce seeds in uneconomical amounts, or when plants are sterile and do not produce viable seeds or when seed cannot be stored (see recalcitrant seeds).
• Micropropagation often produces more robust plants, leading to accelerated growth compared to similar plants produced by conventional methods - like seeds or cuttings.
• Some plants with very small seeds, including most orchids, are most reliably grown from seed in sterile culture.
• A greater number of plants can be produced per square meter and the propagules can be stored longer and in a smaller area.

Disadvantages

Micropropagation is not always the perfect means of multiplying plants. Conditions that limits its use include:

• Labour may make up 50–69% of operating costs.
• All plants produced via micropropagation are genetically identical clones, leading to a lack of overall disease resilience, as all progeny plants may be vulnerable to the same infections.
• An infected plant sample can produce infected progeny. This is uncommon as the stock plants are carefully screened and vetted to prevent culturing plants infected with virus or fungus.
• Not all plants can be successfully tissue cultured, often because the proper medium for growth is not known or the plants produce secondary metabolic chemicals that stunt or kill the explant.
• Sometimes plants or cultivars do not come true to type after being tissue cultured. This is often dependent on the type of explant material utilized during the initiation phase or the result of the age of the cell or propagule line.
• Some plants are very difficult to disinfect of fungal organisms.

The major limitation in the use of micropropagation for many plants is the cost of production; for many plants the use of seeds, which are normally disease free and produced in good numbers, readily produce plants (see orthodox seed) in good numbers at a lower cost. For this reason, many plant breeders do not utilize micropropagation because the cost is prohibitive. Other breeders use it to produce stock plants that are then used for seed multiplication.

Mechanisation of the process could reduce labour costs, but has proven difficult to achieve, despite active attempts to develop technological solutions.

Applications

Micropropagation facilitates the growth, storage, and maintenance of a large number of plants in small spaces, which makes it a cost-effective process. Micropropagation is used for germplasm storage and the protection of endangered species. Micropropagation is widely used in ornamental plants to efficiently produce large quantities of uniform, disease-free specimens, significantly enhancing commercial horticulture operations. Among the species broadly propagated in vitro, one can mention chrysanthemum, damask rose, Saintpaulia ionantha, Zamioculcas zamiifolia and bleeding heart. Micropropagation can also be used with fruit trees, e.g. Pyrus communis. In order to reduce expenditures, natural plant extracts can be used to substitute traditional plant growth regulators.