Diurnal Variations in Micro Environment and Water Relations of Unirrigated and Irrigated Barley

Summary Effect of irrigation was studied on diurnal changes in microenvironment and plant water relations during the grain filling stage in Barley cv. BG 25. An increase in the incident radiation (400–700 nm wave band) decreased the absorption coefficient, but not the absolute absorption of radiation. Different temperatures (soil, ambient air, canopy air, leaf) also followed the course of radiation, but the peak temperatures had a lag of about two h to incident radiation. Soil temperature declined slowly and canopy air and leaf temperatures at a rapid rate in the evening as compared to the ambient air temperature. The increase in radiation decreased the leaf water potential and increased the stomatat conductance, except during the mid-day hours when stomatal conductance decreased at higher photon flux density, irrigated barley showed higher leaf water potential, stomatal conductance, absorption ol radiation, tiller density, yield and lower temperatures (soil, canopy, air, leaf) than unirrigated barley.