Yield, carbon isotope discrimination, canopy reflectance and cuticular conductance of barley isolines of differing glaucousness

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The roles of wax bloom (glaucousness) in discrimination against stable isotope 13C (Δ) and yield were studied for 2 years on a pair of near-isogenic lines of two-rowed barley (Hordeum vulgare L.) differing in their degree of glaucousness of the spike and the upper vegetative parts of the plant other than leaf blades. The effects of glaucousness on canopy reflectance and cuticular conductance were also assessed. Plants were grown under fully irrigated and rainfed Mediterranean conditions for 2 years. Grain yield for both years and total straw biomass measured in the second year were higher in glaucous than nonglaucous lines under both irrigated and rainfed conditions. Δ followed the same pattern in both grain and straw with the highest values in the glaucous line under irrigation and the lowest in the non-glaucous line under rainfed conditions. Differences in yield and Δ between the lines were greater under irrigated than rainfed conditions. The higher Δ of the glaucous line suggests that these plants had lower transpiration efficiency (net photosynthesis to transpiration ratio) than the non-glaucous line in the long term. Canopy reflectance at some of the wavelengths of the PAR region (400–700 nm) was significantly higher in the glaucous than in the non-glaucous line under both irrigated and rainfed conditions. Rainfed conditions also increassed canopy reflectance in the PAR region. No significant effect of either glaucousness or water regime was observed in cuticular conductance or amount of cuticular waxes of the flag leaf blades or the ear.