Abstract:

Leading shoot elongation was analyzed for 63 eucalypt(Eucalyptus)clones over the second year after planted. The data were separately fitted for each clone against a Sigmoid-Logistic mixture of growth function. All fittings were excellent with extremely high goodness of fit (R²>0.99) and significance (P<0.000 1). All four function parameters played their fundamental role in the fitting with significance at level of P<0.000 1 for most cases. Clonal variation obviously exhibited in the characters of shoot elongation and tree growth. All eucalypt clones clearly experienced early and late slow-growing periods and a fast growing period in between. A large part of clones, particularly fast-growing ones, continued to slowly elongate their shoots in the cold winter, while the remaining appeared otherwise. The shoot growth rate of eucalypt clones in the seasons of fall and winter may relate to their susceptibility to low temperature. Main shoot elongation parameters could be used to cluster eucalypt clones and to assist selection of clones for different objectives. It was suggested that the potential planting region would be demarcated into 3 zones, and the corresponding selection and breeding strategies.

Key words: eucalypt (Eucalyptus), clone, leading shoot, elongation, growth function, clonal selection