Diversity of water use efficiency among Quercus robur genotypes: contribution of related leaf traits

Abstract

• Previously, a large intra-specific diversity and a tight genetic control have been shown for Δ 13 C (carbon isotope discrimination) in a pedunculate oak (Quercus robur L.) family, which is an estimator for intrinsic water use efficiency (Wi), a complex trait defined as the ratio of net CO2 assimilation rate (A) to stomatal conductance for water vapour (gs). • In the present study, twelve genotypes with extreme phenotypic values of Δ 13 C were selected within this family to (i) asses the stability of genotype differences across contrasting environments and for different measures Wi; (ii) quantify the relationship between Δ 13 Ca ndWi within this family; (iii) identify which leaf traits drive the diversity in Wi observed in this family. • Genetic variability of Δ 13 Ca ndWi was largely independent from different temporal integration scales and their correlation was found to be strong (R 2 = 88% for leaf sugars) within this family. • Weak correlations between measures of Wi with estimators of photosynthetic capacity, suggest a minor role of the latter in the diversity of Wi. • However, the tight correlation between gs and Δ 13 Ca s well asWi, and the related genotypic variation in stomatal density, suggest that the genotypic diversity in Wi within this pedunculate oak family might be due to differences in gs.