Drought responses of Eucalyptus microtheca provenances depend on seasonality of rainfall in their place of origin

We exposed seedlings of 12 Eucalyptus microtheca F. Muell. provenances to w ell-watered and water-stressed growing conditions in a greenhouse experimen t and investigated the effects of drought on various plant properties in th e provenances. We found significant variation in total biomass, height, roo t mass/foliage area ratio, foliage area/stem cross sectional area ratio, sp ecific leaf area (SLA), water-use efficiency (WUE) and carbon isotope compo sition (delta(13)C) among the provenances. The observed inter-provenance va riation was more pronounced in the water-stressed treatment than in the wel l-watered one. Drought increased root mass/foliage area ratio, foliage area /stem cross sectional area ratio, WUE, delta(13)C and decreased total bioma ss, height, transpiration and SLA. We also analysed relationships between p lant properties and climate of native habitats of the provenances and found that most properties were strongly correlated with mean driest quarter rai nfall. The correlation was positive for total biomass, height, transpiratio n and SLA and negative for root mass/foliage area ratio, foliage area/stem cross sectional area ratio, WUE and delta(13)C. Finally, we evaluated the i ntra-specific variation in foliage area/stem cross sectional area ratio in the context of tree hydraulic architecture: provenances from dry areas and trees grown under drought stress had more foliage per stem area ratio. Howe ver, their transpiration and the length of their hydraulic pathway were sma ller and therefore the root to leaf water potential gradient might be small er in these trees.