Leaf Water Content and Gas-Exchange Parameters of Two Wheat Genotypes Differing in Drought Resistance
- Steven W. Ritchie,
- Henry T. Nguyen and
- A. Scott Holaday
It is still unclear what parameter(s), other than grain yield, might be a suitable indicator in a wheat (Triticum aestivum L.) breeding program for drought resistance. In this study, the leaf relative water content (RWC) and gas-exchange parameters were compared between a drought-resistant winter wheat genotype (cv. TAM W-101) and a drought-susceptible genotype (cv. Sturdy) to determine if these physiological parameters contribute to drought resistance in TAM W-101. Plants were grown under well-watered conditions in growth chambers until drought stress was imposed by limited watering of plants at anthesis or during vegetative growth. In both growth stages, TAM W-101 maintained a higher RWC and apparent photosynthesis (A) than Sturdy under moderate to severe drought stress. TAM W-101 plants also maintained a higher photosynthetic capacity (higher A at a given intercellular CO2 concentration [Ci]) under stress than did Sturdy in both growth stages. Photosynthetic water use efficiency (pWUE = A/stomatal conductance) generally increased with stress severity until very severe stress levels were attained. Thus, genotypic pWUE comparisons using stressed plants should be evaluated on a water-status basis (e.g., RWC) to avoid the confounding effect of stress severity on pWUE. TAM W-101 tended to have higher pWUE (RWC basis) than Sturdy under moderate to severe stress conditions, but not under well-watered conditions. High leaf RWC, A, and photosynthetic capacity are traits that may contribute to drought resistance in TAM W-101.
Copyright © 1990.