Effect of deficit irrigation and super absorbent application on physiological characteristics and seed yield of new Iranian sunflower (Helianthus annuus L.) hybrids

To evaluate the effects of deficit irrigation and super absorbent application on physiological traits and seed yield of new sunflower hybrids, a field experiment was conducted in split plot factorial layout based on randomized complete block design with three replications in Agricultural Research Station of Islamabad-e-Gharb, Iran, during cropping seasons 2011 and 2012. Treatments were irrigation levels including; normal irrigation (irrigation at 25% soil moisture depletion of field capacity), irrigation at 50% soil moisture depletion of field capacity (moderate drought stress), irrigation at 75% soil moisture depletion of field capacity (severe drought stress) as main plots and sunflower hybrids (Farokh, Ghasem and Shams) along with super absorbent application (0, 100 and 200 kg.ha-1) as subplots, were arranged in factorial layout. Results of combined analysis of variance showed that the interaction effect of deficit irrigation´hybrids on all plat traits and super absorbent´hybrids on all plant trraits (except for osmotic adjustment and cell membrane stability) and deficit irrigation´super absorbent o all plant traits (except for seed yield and cell membrane stability), were significant. Under severe drought stress condition, Farokh hybrid with 3071 kg.ha-1 was superior compare to Shams and Ghasem hybrids (with 2710 and 2601 kg.ha-1, respectively). Under severe drought stress codition, the application of super absorbent increased relative water content, free proline, proteins and soluble sugars content in sunflower hybrids, but reduced osmotic adjustment. It concluded that the application of super absorbent may relatively mitigate the adverse effects of drought stress on physiological traits of sunflower. Under drought stress condition, Farrokh hybrid along with application of super adsorbent (200 kg.ha-1) was superior in all plant traits compared to other hybrids.