Assessment of Antioxidant Activity, Grain and Oil Production of Amaranth (Amaranthus retroflexus L.) in Saline Conditions

Salt stress is one of the major factors limiting crop productivity worldwide. Grain amaranth is new crop with high yield potential and good nutrition value which can be a good substitute for salt-sensitive crops in saline areas. This research was conducted to evaluate different level of salinity and applied salinity stress at several growth stages on some morphological and physiological traits of Amaranth via split plot experiment based on completely randomized with three replications. The main factor included five level of salinity (Control, 75, 150, 225 and 300 mM NaCl). The sub factor consisted applied salinity stress at four growth stages (Plant establishment, branching, flowering and grain filling period) under hydroponic system with Hoagland solution. According result of analysis of variance interaction applying different levels of salinity at different growth stages was significant at 1% probability level for all traits (instead hydrogen peroxide; H2O2, malon di aldehyde; MDA and total phenolic). Mean comparison results showed that application of 300 mM salinity concentration after plant establishment stage led to death of amaranth. Salinity application after establishment decreased significantly plant height, number of branches and panicle per plant as 44.9, 31.8 and 35.4%, respectively. Root volume only decreased after salinity 225 mM after plant establishment and 300 mM at the branching as 38 and 45%, respectively. Production of grain weight was not affected by 75 mM salinity, but at higher salinity showed significant decrease. The highest decrease in grain weight obtained by applying 225 mM salinity after the plant establishment and salinity at 300 mM after branching as 86.6 and 71.3%, respectively, resulting in a decrease in both 1000 kernel weight and grain number, respectively. Salinity application increased H2O2, MDA and total phenolics contents, severely. Most of characteristics were not affecting by 75 mM NaCl, but other concentrations had a negative effect on the growth and production of amaranth. In this study, the most sensitive application time to salinity was after plant establishment and the most tolerant was grain filling stage.