Silicon-mediated growth and yield improvement of sunflower (Helianthus annus L.) subjected to brackish water stress

Abstract

Silicon is known to compensate crop yield losses under diverse biotic and abiotic stress conditions; however, reports about its protective role for plants exposed to brackish water stress are very limited. A pot culture experiment was conducted to assess the beneficial effect of silicon supplementation (0 and 100 mg/kg) in alleviating growth adversities of brackish water (saline, sodic, alkaline, and saline–sodic water) stress in two contrasting sunflower cultivars, SF-187 (salt tolerant), and Hysun-33 (salt sensitive) grown in greenhouse. Results demonstrated that hostile growth environments, mainly the combined stress of saline–sodic water, severely affected the physiological attributes, growth, yield, and yield contributing components in sunflower. However, the response to brackish water stress differed genotypically, with greater magnitude of damage to the Hysun-33 as compared to SF-187 genotype. It hampered plant growth due to membrane damage and reduced water uptake, but silicon supplementation minimized the negative effects of stress by limiting toxic Na+ ions uptake, improving membrane stability, and increasing relative water contents caused by higher silicon and K+ uptake that eventually led to improved biomass yield. The response was further evaluated at yield level and data regarding head diameter, achene yield, and 100 achene weight were taken. Results indicated that silicon supplementation to growth medium of saline and/or sodic water treated plants significantly enhanced the head diameter (22–30%), thus ultimately producing 15–25% higher achene yield, and weight of the biological harvest of both sunflower genotypes. Overall, the beneficial effect of silicon supplementation was more evident in Hysun-33 (salt sensitive) as compared to SF-187 (salt tolerant) genotype. Taken together, the results of this study suggest silicon fertilization as a potential strategy to increase crop productivity under brackish water stress; however, experimental trials at farmer field level should be conducted before setting any recommendations.