Effects of foliar micronutrient application on osmotic adjustments, grain yield and yield components in sunflower (Alstar cultivar) under water stress at three stages

In order to study the effects of foliar micronutrient application under water stress, at three stages of growth, on prolinee and carbohydrate concentration, grain yield and yield components of sunflower (Alstar cultivar), a field experimental in split plot design with three replications was conducted in 2007. Alstar cultivar was comprised under water stress at three stages of growth (heading, flowering and grain filling) as main plot and seven micronutrient treatments, Fe, Zn, Mn, Fe+Zn, Fe+Mn, Zn+Mn and Fe+Zn+Mn, as sub-plots. Results showed that water stress at three stages of growth significantly decreased grain yield, biological yield, 1000 weight seeds, cap diameter and cap weight of sunflower (Alstar cultivar). The impact of water stress was more pronounced when applied at grain filling. Use of foliar micronutrient increased grain yield in water stress on the other hand, use of Mn foliar application had the highest positive effect on yield components and grain yield. Free prolinee and total soluble carbohydrate concentration were increased under water stress, at all of the three stages of growth. The highest concentration of these two components was found on the flowering stage.   Key words: Water stress, micronutrient, grain yield, osmotic adjustment, sunflower.