Investigation of antioxidant activities and biochemical characteristics of drought-stressed fenugreek (Trigonella foenum- graecum L.) in response to biopotasse and iron sulfate

In order to investigate the effect of biopotasse and iron sulfate on antioxidant activity and biochemical characteristics of fenugreek under drought stress conditions, a factorial experiment was conducted as split plot based on randomized complete block design with three replications in 2017. Treatments included drought stress (normal irrigation as non-stress and irrigation in early growth for 14 days as drought stress) as the main factor and biopotasse (0 and 5 kg. ha-1) and iron sulfate (0 and 1.5 per thousand) as sub-factors biofertilizer. Results showed that the effect of drought stress, biopotasse, iron sulfate, and their interaction were significant on anthocyanin and phenolic compounds and flavonoids so that the highest amount of anthocyanin in fenugreek was obtained from 5 kg biopotasse treatment per hectare and 1.5 per thousand iron sulfate in drought stress conditions while the lowest amount was recorded in control treatment under stress conditions. Also, in drought stress, phenolic compounds, and flavonoids increased in fenugreek, as the highest amount of total flavonoid was achieved under drought stress conditions and 5 kg ha-1 biopotasse and 1.5 per thousand iron sulfates. The interaction of drought stress and iron sulfate was significant on the antioxidant activity of the plant, as the highest antioxidant activity (62.8%) was obtained in drought stress and iron sulfate treatment. Also, the highest amount of total carbohydrate in fenugreek was obtained under drought stress conditions and in 5 kg biopotasse treatment, and the lowest trait was obtained under non-stress conditions. Results showed that the highest total chlorophyll content of fenugreek was observed in non-drought stress conditions and 5kg .ha-1 biopotasse and iron sulfate 1.5 per thousand. Based on the findings, drought stress played an important role in increasing phenolic compounds, flavonoids, anthocyanin, and soluble sugar contents of fenugreek and biopotasse biofertilizer and iron sulfate improved biochemical characteristics of the plants.