YIELD, CARBON-ISOTOPE DISCRIMINATION, CANOPY REFLECTANCE AND CUTICULAR CONDUCTANCE OF BARLEY ISOLINES OF DIFFERING GLAUCOUSNESS

The roles of wax bloom (glaucousness) in discrimination against stable isotope C-13 (Delta) 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 glaucousnes s on canopy reflectance and cuticular conductance were also assessed. Plants were grown under fully irrigated and rainfed Mediterranean cond itions for 2 years. Grain yield for both years and total straw biomass measured in the second year were higher in glaucous than non-glaucous lines under both irrigated and rainfed conditions. Delta followed the same pattern in both grain and straw with the highest values in the g laucous line under irrigation and the lowest in the non-glaucous line under rainfed conditions. Differences in yield and Delta between the l ines were greater under irrigated than rainfed conditions. The higher Delta of the glaucous line suggests that these plants had lower transp iration efficiency (net photosynthesis to transpiration ratio) than th e non-glaucous line in the long term. Canopy reflectance at some of th e 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 reflect ance in the PAR region, No significant effect of either glaucousness o r water regime was observed in cuticular conductance or amount of cuti cular waxes of the flag leaf blades or the ear.