Effect of zinc and sulfur foliar applications on physiological characteristics of sunflower (Helianthus annuus L.) under water deficit stress

In order to study effect of zinc and sulfur foliar applications on quantitative and qualitative characteristics of sunflower under water deficit stress, an experiment was conducted at Varamin, Iran during 2013 growing season. The experimental design was laid out in a randomized complete block with a split plots arrangement of treatments in three replications. Main plots included three different levels of irrigation (complete irrigation, irrigation withholding at flowering stage and irrigation withholding at seed filling period stage) and sub plots were included four different zinc and sulfur application (untreated zinc and sulfur application, zinc foliar application, sulfur application and both zinc foliar application and sulfur application). The results showed that irrigation withholding at different growth stages significantly decreased seed number in cap, thousand seed weight, seed yield, biological yield, oil yield and total chlorophyll but by contrast increased proline content, membrane stability, super oxide dismutase enzymes activity. Both zinc foliar application and sulfur application treatment had positive effect on all attributes in this experiment. In general, the results of the present study indicate that usage of zinc foliar application reduces the harmful effects of water deficit stress and increases resistance to drought stress in sunflower plant.