Effect of slow release urea-hydrogel complex on chlorophyll fluorescence and morphological traits of barley under drought stress

To study the effect of slow release hydrogel-urea complex (SRHUC) on chlorophyll fluorescence and morphological parameters of barley under drought stress, an experiment was performed in 2017-2018 as factorial in Randomized Complete Block Design (RCBD) with three replications in the greenhouse of Aburaihan campus of University of Tehran. The combination of factorial levels were as fertilization factor containing nitrogen (N) from urea source in five levels of no N application, equivalent 125 and 65 kg.ha-1 N without and with SRHUC as CU-N125, CU-N65, SRHUC-N125 and SRHUC-N65, respectivly and drought stress in three levels of 70, 50 and 30% FC. Drought stress decreased flag leaf area and the lowest value (13.12 cm2) belonged to 30% FC. Furthermoreit decreased flag leaf dry weight, total number of tiller and SPAD index. SRHUC-N125, SRHUC-N65 and CU-N125 have showed the highest values of maximum (Fm) and variable (Fv) fluorescences. In 50% FC, N-containing treatmenats had the highest Fv/Fo and SRHUC treatments showed the highest performance index based on absorption (PIABS) that were equal to 1.66 and 1.60. In 30% FC, the lowest value (10913) of minimum fluorescence (Fo) was related to SRHUC-N125. SRHUC-N125 caused the highest flag leaf area (16.8cm2), stem diameter (4.2 mm) and SPAD index (43.6). It can be concluded that better N availability in Goharan cultivar, had favorable effects on chlorophyll fluorescence and growth parameters, especially in drought stress, and SRHUC application might result in more appropriate chlorophyll fluorescence and growth characteristics.