Carbon isotope composition, water-use efficiency and biomass productivity of Eucalyptus microtheca populations under different water supplies

Variation in carbon isotope composition (delta(13)C), water-use efficiency (WUE) and biomass productivity were compared among three populations of Eucalyptus microtheca F. Muell. in a greenhouse. Seedlings were maintained under one well-watered (Control, keeping the soil at field capacity) and two different water deficit conditions (Drought stress I, keeping the same soil water content; Drought stress II, keeping the same soil water supply). In each treatment, significant population differences in delta(13)C, WUE, and dry matter accumulation and allocation were detected. A negative correlation between WUE and biomass productivity was detected under control and drought stress I, but a positive correlation under drought stress II. The results suggested that there were different water-use strategies among the populations, the southeastern population with lower WUE may employ a prodigal water-use strategy, whereas the northwestern and central populations with higher WUE may employ a conservative water-use strategy. This knowledge may be useful as criteria for genotype selection within a breeding program for this species.