Modification of some growth indices in wheat under water deficit conditions

The experiment was conducted during 2004-2006 growing seasons at the Agricultural Research Station, Islamic Azad University, Naragh Branch, to evaluate the effects of water deficit on growth indices of three bread wheat (Triticum aestivum L.) cultivars. A split plot experiment based on a randomized complete block design with four replications was used in both years. Irrigation treatments (irrigation after 70 (I1), 90 (I2) and 110 (I3) mm of cumulative evaporation from class A evaporation pan) were considered as the main plot and wheat cultivars (Mahdavy, Sepahan and Roshan-back cross) as subplots. Irrigation after 70 and 90 mm cumulative evaporations did not modify growth indices, significantly. Delay in irrigation from 90 to 110 mm cumulative pan evaporation significantly reduced the growth indices. Pattren of changes in leaf area index (LAI), total dry matter (TDM), net assimilation rate (NAR), and crop growth rate (CGR) were similar in both 70 and 90 mm treatments. At samplings, delay in irrigation from 90 to 110 mm cumulative evaporation lowered the incraese of all growth indices. Pattern of changes in CGR was more similar to LAI but dissimilar to NAR. The results indicated that 22% water could be saved when wheat plants were irrigated after 90 mm of cumulative pan evaporation. However, a decrease of growth indices and grain yield under this water condition was not important.