Tissue culture and beyond
Some plants produce seeds that are not suitable for seed-banking; other plants do not produce seed at all. An alternative way to conserve these species is to culture and bank their tissues.
Tissue culture involves taking very small pieces of plant (buds, shoot tips, or other parts) and growing them on special nutrient media in sterile conditions. This method allows the production of many plants from a single shoot - a great advantage when plants are rare. Many house and garden plants available in nurseries are grown by tissue culture.
Tissue culture can be used to produce identical copies (clones) of a plant that has desirable features. For many years, flannel flowers (Actinotus helianthi) were harvested from the wild for the cut-flower trade, sometimes unsustainably. Scientists here have developed a number of flannel flowers suited to cultivation. Using tissue culture techniques, these plants are grown by the thousands and made available for sale to gardeners around Australia.
Orchid seeds cannot germinate unless they are associated with a particular kind of fungus. The fungus grows into the seed and provides the nutrients that allow the embryo to germinate and grow. Tissue culture is used to mimic this natural process in the laboratory. The seeds and fungus are cultured together, resulting in the propagation of healthy orchid plants.
Cryo-storage involves immersing plant tissues and seeds in vats of liquid nitrogen at temperatures as low as -196°C. Under these conditions, plant tissue ages very slowly and can be kept in storage almost indefinitely. Cryo-storage of plant tissue is an alternative for preserving rainforest species, many of which have seeds that cannot be conserved by drying and freezing in the vault.