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

Abstract

We exposed seedlings of 12 Eucalyptus microtheca F. Muell. provenances to well-watered and water-stressed growing conditions in a greenhouse experiment and investigated the effects of drought on various plant properties in the provenances. We found significant variation in total biomass, height, root mass/foliage area ratio,foliage area/stem cross sectional area ratio, specific leaf area (SLA), water-use efficiency (WUE) and carbon isotope composition (d ¹³ C) among the provenances. The observed inter-provenance variation was more pronounced in the water-stressed treatment than in the well-watered one. Drought increased root mass/foliage area ratio, foliage area/stem cross sectional area ratio, WUE, d ¹³ C and decreased total biomass, height, transpiration and SLA. We also analysed relationships between plant properties and climate of native habitats of the provenances and found that most properties were strongly correlated with mean driest quarter rainfall. The correlation was positive for total biomass, height, transpiration and SLA and negative for root mass/foliage area ratio, foliage area/stem cross sectional area ratio, WUE and d ¹³ C. Finally, we evaluated the intra-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. However, their transpiration and the length of their hydraulic pathway were smaller and therefore the root to leaf water potential gradient might be smaller in these trees.