GROWTH RESPONSE OF <em>EUCALYPTUS</em> <em>MICROTHECA</em> PROVENANCES TO WATER STRESS

Abstract

Growth variation was observed under three watering regimes in a greenhouse experiment among four Eucalyptus microtheca provenances whose natural habitats represented a gradient of different climatic conditions. Compared with provenances from northern and central Australia, southeastern Australian provenances showed a faster early seedling growth in the different treatments. There were significant correlations between shoot biomass, total biomass or total leaf area and driest-quarter rainfall of the natural habitats of the provenances. The pattern of shoot height growth for each provenance in relation to the watering regime indicated a linear regression in the control treatment, whereas the growth response followed a curvilinear regression under water stress. In addition, statistically significant differences in leaf stomatal length were detected between the provenances. These results were interpreted as suggesting that there are different adaptive strategies in response to water deficit among the provenances of this eucalypt species which are manifested when the provenances are grown outside their natural Australian range. It is suggested that the northern and central provenances would not be able to take advantage of favourable hydrological conditions, to the extent the southeastern Australian provenances would do in a similar situation.