Introduction
The importance of eucalypts and reasons for tissue culture Eucalypts are Australia's most distinctive plant group. They are contained within the genus Eucalyptus which consists of over 500 named species, with more as yet unnamed (Brooker & Kleinig 1983; 1990 Chippendale 1988). The natural distribution of the genus is almost completely confined to the Australian continent and Tasmania with only two species, E. deglupta and E. urophylla, occurring naturally in other countries. Since European settlement of Australia, seeds of eucalypts have been sent to countries throughout the world and they are now commonly grown in tropical and temperate areas for timber, pulp wood, eucalyptus oil, fuelwood, charcoal and as ornamentals.
Exploitation of eucalypts outside Australia was initiated by the French. During the nineteenth century, eucalypts were planted in Europe and North America, and European imperial governments introduced them to colonies in South America, Africa and Asia. The presence of eucalypts in some of these countries is now so familiar to the native peoples that many consider them to be indigenous (Zacharin 1978).
Although eucalypts in early plantations often grew very quickly the wood was sometimes of poor quality due to wood splitting and distortion (Clarke 1957; Penfold & Willis 1961; Pryor 1976). In many cases this was because the species chosen were inappropriate for local climatic and edaphic conditions (Evans 1980; Durand-Cresswell et al. 1982), the trees had been planted for the wrong purposes (Penfold & Willis 1961; Pryor 1976), or given incorrect fertilisers (Savory 1962; Stone 1968).
The poor quality of the wood led to a slump in enthusiasm for growing eucalypts until about 1945 when world demand for pulpwood started to increase (Pryor 1976). Today the major uses of eucalypt wood are for fuelwood and pulpwood. There has been a 150 fold increase in pulpwood production from eucalypts since the early 1960s (Molleda 1984). They are now the most widely planted hardwood group in the world (Boland et al. 1984; Eldridge et al. 1993)
