This method uses explants, or tiny pieces of young plant material. A microscopic portion of plant tissue is extracted from a plant under sterile conditions and is then divided and grown on in test-tube conditions. The test-tube is a glass or plastic container with a medium that contains organic nutrients, mineral salts, hormones and other elements needed for growth. The test-tube is then placed in a closely controlled, sterile environment. The explants multiply to form numerous shoots or complete plantlets. They are then rooted as micro-cuttings or if they already have roots, they are weaned to greenhouse conditions. Sterile conditions are vital throughput and transfer of the plant material from the culture medium to a greenhouse conditions is difficult.
Micropropagation is used mainly for high-value plants, for rapid introduction of new cultivars, for plants that re difficult to be propagated by other methods and also is used for producing disease-free stock.
Also known as genetic engineering, this method uses modern DNA technology to identify and extract particular genes from a plant’s cells and introduce them into another cell, not necessarily of the same species. This method is used to obtain plants resistant to certain pests and diseases, to extend color and scent ranges in flowers, to enhance fruit flavors, to obtain plants with greater tolerance of low temperatures and water shortage and for production of medicinal compounds.
There are still many questions and concerns about using this method and its potential risks to the environment.
Advances in seed propagation
There have been developed new methods to improve the speed and uniformity of seeds germination for the gardeners. Seeds are soaked in solutions of salts, like sodium chloride or potassium nitrate, or in polyethylene glycol solutions. They are thus primed for germination but are dried before the radicle emerges and are then packaged ready for sale. These seeds can be sown conventionally as required.
Fluid drilling and pelleted seeds have been developed to make uniform sowing easier. In fluid drilling, seeds primed for germination are contained within a gel base, like a fungicide-free wallpaper paste, which can be squeezed along the seed drill. In pelleted seeds, primed seeds are coated in an inert material that may contain fungicides, nutrients and/or a fluorescent dye. These readily handled seeds can be sown very evenly.
Artificially produced seeds
Some flower tissues, when introduced into a special liquid culture medium, develop numerous embryos. Each of these embryos is similar to the embryo within a seed. If these are given a synthetic coating, in a process known as somatic embryogenesis, vast numbers of genetically uniform, artificial seeds may eventually be produced.