Do the herbicides pinoxaden, tribenuron-methyl, and pyroxsulam influence wheat (Triticum aestivum L.) physiological...

Herbicides reduce the unsafe effects of weeds, but they are likely to have negative impact on essential and secondary metabolism in crops. However, the combined effect of different herbicides on chemical constituents of different varieties of wheat is still not fully obvious. The current investigation was carried out to determine the effects of three post-emergence herbicides (pinoxaden, tribenuron-methyl, and pyroxsulam) on total protein, lipid, and carbohydrate concentrations of three bread wheat cultivars (Misr 1, Giza 171, and Gemmiza 11). These herbicides were added individually and in combinations at recommended and/or half recommended doses. Our findings revealed that the individual application of herbicides decreased total protein and total lipid concentrations in fresh shoots of the three studied wheat cultivars, but increased total carbohydrate concentration. Combined addition of herbicides at recommended and half recommended doses generally decreased the concentrations of total proteins, total lipids, and total carbohydrates. However, the combined addition of tribenuron-methyl and pinoxaden at recommended dose enhanced total protein and total lipid concentrations under Misr1 and Gemmiza 11 cultivars compared to control treatment. Furthermore, the combined addition of tribenuron-methyl and pyroxsulam at half recommended dose enhanced total protein concentration in Giza 171 up to 15.05% and Gemmiza 11 up to 15.09% cultivars, and total lipid concentration in Misr 1 (7.53%) and Giza 171 (9.81%) cultivars against control treatment, where it was the lowest. Total carbohydrate concentration was enhanced by the sole application of pinoxaden by 53.55%, 52.40%, and 51.79% for Misr 1, Giza 171, and Gemmiza 11 cultivars, respectively. Moreover, individual or combined additions of the studied pesticides at recommended and half recommended doses negatively affected wheat grains under all cultivars via decreasing their concentration of nutrients (nitrogen, phosphorus, and potassium) as well as total protein and total carbohydrates. The highest reduction of nitrogen, phosphorus, and potassium concentrations compared to control was observed when tribenuron-methyl+pyroxsulam was applied at the half recommended dose under the three studied cultivars. However, the combined application of tribenuron-methyl+pyroxsulam at the half recommended dose caused the great depression in total proteins and total carbohydrates of wheat grains. Under the stress effect of herbicides, individual application of pinoxaden gave the best results for nitrogen and potassium content as well as total protein and total carbohydrate concentrations in the three studied wheat grain cultivars.