Although propagation techniques using seed or vegetative material (such as cuttings) are the commonest ways of producing new plants, there are many other techniques that are being used for special situations. Many require specialised knowledge and have been developed to facilitate genetic breeding and early production of fruit and seed.
Grafting - and budding - involves the attaching of a shoot (scion) or a bud onto a suitable root stock. A variety of techniques have been developed to maintain close contact of the tissues until they have grown together. The technique has been used in agriculture for a long time to propagate varieties of plants that cannot be reproduced effectively by normal means. This may be because they are sterile or cannot be bred true, or the time taken to fruit and seed is too long. Grafting is used extensively in horticulture for fruit trees, and is used in forestry principally as a technique to facilitate genetic improvement through clonal propagation and for seed multiplication.
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Micropropagation - involves the production of plants from very small plant parts, tissues, or cells grown under strictly controlled conditions in the laboratory. The aim is to multiply material for research purposes, or as a first step in a large planting programme to rapidly increase desirable genetic stock. The techniques have developed from tissue culture, and include somatic embryogenesis ( i.e. the regeneration of embryo-like structures from callus cell suspensions). The young material are referred to as micropropagules. Although procedures have been successfully developed for both hardwoods and conifers, the cost is high and it is not always certain how well the micropropagules will develop in the field.
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