Leaf traits indicative of drought resistance in hybrid poplar

Intensively managed poplar plantations (Populus spp. and their hybrids) have the potential to provide large quantities of renewable biomass for bioenergy. Identifying clonal varieties that are productive on water-limited, marginal agricultural land unsuitable for food production with low land costs is key to realizing that potential. Carbon isotope discrimination (Delta C-13) is the current method of choice for selecting varieties able to maintain higher levels of production under moderate drought stress (drought resistance). However, other physiological and morphological traits may be effective as selection criteria for drought stress and cost less to collect and analyze. The objective of this study was to test the efficacy of Delta C-13, along with alternative physiological and morphological traits, in predicting drought resistance of hybrid poplar varieties. The other traits considered were leaf mass per area (LMA), petiole diameter (PD), petiole length (PL), individual leaf area (LA), adaxial stomatal density (ADAX), abaxial stomatal density (ABAX), minor vein density (MVD) and chlorophyll content (CHLOR). We found that Delta C-13 was a poor indicator of drought resistance and ABAX was the only single trait that was a statistically significant predictor of varietal performance under drought stress. The best indicator of drought stress was a composite of all nine variables.

Automated summary

Intensively managed poplar plantations have the potential to provide renewable biomass for bioenergy production, with clonal varieties being crucial for productivity on water-limited, marginal agricultural land. While carbon isotope discrimination is commonly used for selecting drought-resistant varieties, this study found that other traits like abaxial stomatal density were more accurate predictors of varietal performance under drought stress. A composite of all nine variables proved to be the best indicator of drought resistance in hybrid poplar varieties.