EPICUTICULAR WAX PRODUCTION, WATER STATUS AND LEAF TEMPERATURE IN TRITICEAE RANGE GRASSES OF CONTRASTING VISIBLE GLAUCOUSNESS

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Abstract
Studies were conducted to compare the effect of glaucousness on the response of perennial range grasses to drought stress. Glaucous and nonglaucous plants of an intermediate wheatgrass hybrid (Thinopyrum intermedium (Host) Barkworth and D. R. Dewey × T. intermedium-acutum D.R. Dewey pers. commun.) and an interspecific hybrid of crested wheatgrass (induced tetraploid Agropyron cristatum (L.) Gaertner s. lat. × A. desertorum (Fisch. ex Link) Schultes) were studied in field nurseries for epicuticular wax production, leaf water potential, leaf reflectance of radiation and leaf temperature. Glaucous plants of intermediate wheatgrass had higher epicuticular wax production, increased leaf reflection of radiation, lower midday canopy temperatures, and higher predawn leaf water potentials than non-glaucous plants. Similar trends were observed for the crested wheatgrass hybrids except that glaucousness did not affect midday plant temperatures. A greenhouse experiment involved comparison of glaucous and non-glaucous synthetics of Altai wild ryegrass (Leymus angustus (Trin.) Pilger Dewey). Leaves of glaucous Altai wild ryegrass reflected more radiation and used water less efficiently (total biomass basis) at high soil water content than leaves of the nonglaucous synthetic. At low soil water content, glaucous Altai wild ryegrass had higher leaf temperature and higher midday leaf water potential. Glaucous and nonglaucous Altai synthetics did not differ significantly for shoot yield, total biomass yield, and water use efficiency (shoot yield basis) at either soil water content. While glaucousness may affect water relations of these grasses, it does not necessarily affect forage yield.Key words: Water use efficiency, drought stress, leaf radiation reflectance, crested wheatgrass, intermediate wheatgrass, Altai wild ryegrass