Measurement and Use of Excised-Leaf Water Status in Wheat
1989
McCaig, T. N. | Romagosa, I.
Water status of intact and excised leaves has been reported to be related to drought resistance. Automation of leaf weighing has enabled more rapid and detailed examination of water content and water loss following excision than was previously possible. Our objective was to evaluate these measurements as screening techniques in tetraploid wheat (Triticum turgidum L.) and hexaploid wheat (Triticum aestivum L.) breeding programs. Among eight genotypes, those adapted to dryland exhibited high initial water content (IWC) (dry weight basis) and/or low rate of water loss (RWL) suggesting that both characters may contribute to the maintenance of leaf water status during periods of severe drought. Differences among tetraploid genotypes, for IWC and RWL, were more consistent than among hexaploid types. Both IWC and RWL of the most recently fully expanded (MRFE) leaf decreased as a function of thermal time indicating that maturity differences among genotypes must be considered. Genotypic differences were more pronounced when sampling was carried out prior to heading. Leaf selection was also important since the RWL of the MRFE leaf of the main stem was lower than that of the penultimate leaf. Controlled environment (well-watered) results were similar to those obtained from the field (rainfed), indicating that screening may be possible in growth chambers. Phenological, genotypic, and environmental effects on these parameters are further discussed, including procedures and cautions concerning the use of these techniques.
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