Effects of late-season water stress on seed quality and growth indices of durum wheat at different seed densities

An experiment was conducted to evaluate the effects of different levels of water stress and plant density on yield, grain quality and physiological growth indices of durum wheatin agriculture and natural resource research center of Tehran province, during 2010-11. The experiment was organized as a split plot layout based on a randomized complete block design with 3 replications. Three levels of irrigation were tested in the main plots: normal irrigation, irrigation termination at the beginning of the grain filling stage (light stress) and irrigation termination at the beginning of the flowering stage (severe stress). Three levels of plant density were tested in subplots consisting of 350, 450 and 550 plants per m 2 . The results showed that grain yield, protein percentage and leaf proline content were significantly affected by drought stress at the reproductive growth stage. The effects of plant density on all yield components except grain protein percentage and leaf proline content were significant. Wheat grain yield decreased significantly in both levels of light and severe stress compared with the non-stress treatment by 8.6% and 16.2% respectively. The most significant effect of light stress was on TKW and number of fertile spikes, but number of grains per spike, biological yield and green leaf duration were affected by severe stress treatment. Drought stress caused a significant increase on grain protein percentage but had a significant decrease on grain protein yield. Leaf proline content increased under both stress treatments. Increasing plant density from 350 to 450 plants per m 2 improved yield and yield components. The highest grain yield was obtained from 450 plants per m 2 treatment (7212 kg/hac). Grain yield decreased in 550 plants per m2 treatment but the least was for 350 plants per m2. Plant density had a non-significant effect on grain protein percentage but a significant effect on grain protein yield. LAI, CGR and NAR were affected by both irrigation and plant density. Stress treatments caused earlier leaf defoliation and decreased the leaf area duration that finally decreased grain yield. Amounts and time taken to maximize LAI and CGR were significantly affected by plant density.