Leaf water content and gas-exchange parameters of two wheat genotypes differing in drought resistance.
1990
Ritchie S.W. | Nguyen H.T. | Holaday A.S.
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.
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