Investigating the effect of Humic acid treatment on antioxidant capacity, phenol and photosynthetic pigments of the medicinal plant Artemisia annua L. under salt stress

Salinity is one of the most important abiotic stresses that, depending on the type of plant,reduces the ability to produce crops.In order to investigate the effect of different concentrations of Humic acid on decreasing adverse effects of salinity in the Artemisia annua plant,a field pot experiment with three replications was conducted in the form of a factorial randomized complete blocks design at Sari University of Agricultural Sciences and Natural Resources.The experimental treatments included three levels of Humic acid(0,150and300 mg/l)and three levels of salinity(laboratory NaCl:0,4 and 6 g/l).After applying the treatments and during the vegetative growth stage,samples were collected from the aerial parts, and the antioxidant capacity(DPPH),the amount of phenol(folinciocalto),flavonoid(aluminum chloride),photosynthetic pigment, proline and plant biomass were analyzed.The results showed that the application of Humic acid(300 mg/litre)and salinity(especially at 6 g/liter)respectively with the average 0.13, 0.39, 0.61, 6/18(mg/g fresh weight)and 20.92(μg/ml)could effectively increase the Artemisia annua photosynthetic pigments.The use of humic acid with a concentration of300 mg/liter and salinity(especially at a concentration of 4 g/liter)with an average of 2.39(mg of gallic acid per100g)and0.115(mg of quercetin per100g),respectively,in increasing the amount of phenol And flavonoid was effective.The maximum biomass of aerial organs was observed in the treatment of 150 mg/liter of humic acid and no application of salt with an average of15.5%.Therefore, Humic acid can partially compensate for the destructive effects of salinity in Artemisia annua.Using abiotic stresses(saline stress)and organic fertilizers(Humic acid)and combining these treatments at different concentrations could improve some morphological and biochemical characteristics in Artemisia annua, depending on the intended purpose.