Effects of heat stress on human health and physio-biochemical attributes of quinoa growing in arsenic contaminated soil

Heat stress and soil arsenic (As) contamination are resulting in severe decline in crop production around the world. The present experiment aimed to assess physiological and biochemical changes induced by the combination of As and heat stress in quinoa. Plants were grown in pots with different concentrations of As (0, 10, 20, and 30 mg kg−1), either at ambient temperature (30/12 °C day/night) or 5 °C higher than ambient temperature. The combination of heat stress with As (30 mg kg−1 soil) resulted in the highest decrease in shoot/root dry weight (84.1/79.1%), stomatal conductance (84.5%), and leaf relative water contents (75.6%). Heat stress also increased As accumulation in plants, and plants treated with As level of 30 mg As kg−1, with or without heat stress failed to reach maturity. Over expression of antioxidant enzymes partly neutralized the oxidative stress in quinoa caused by As and heat stress. Accumulation of As in quinoa plant parts was in the order of root > shoot > grains. Human health risks posed by the contaminated quinoa grains were increased under the combination of As and heat stress. Hence, cultivation of quinoa genotype Puno is not suitable under high temperatures and contaminated soils with higher As levels. This is the pioneer study exploring the impact of heat stress on As uptake and associated physiological and biochemical attributes of quinoa. The phytotoxicity of As to quinoa was increased under heat stress compared to normal temperature. Due to higher accumulation of As in quinoa grains, the human health risks were also increased under heat stress conditions. Therefore, quinoa genotype Puno is not suitable for cultivation in regions with high temperatures having soils contaminated with higher As levels.