Comparative study of influence of water stress on effectiveness of sulfosulfuron to two species of weeds through biomass and photo-physiological parameters

Abstract

Drought may affect the effectiveness of herbicides. However, our knowledge about the interaction between drought and the response of different species to the application of herbicides is limited. Dose-response experiments were conducted on two major weeds of wheat fields to investigate the water stress effects on sulfosulfuron effectiveness. At the 2-leaf stage, Hordeum spontaneum and Sinapis arvensis were subjected to two irrigation regimes (10 and 65% of the available water depletion) and 7 days later, the plants were exposed to sulfosulfuron doses (0, 50, 100, 200, 400, 800% of the recommended dose). The biochemical and physiological responses of the plants were investigated 10 days later. H. spontaneum showed lower sensitivity to the herbicide than S. arvensis. Water stress decreased the efficiency of sulfosulfuron on both species with a greater effect on H. spontaneum. The herbicide required to induce 90% reduction of total dry mass (ED90) in water-stressed H. spontaneum was 63248.0 g ai ha−1 (2377.7 times the recommended dose of herbicide), and this amount was 10.74 times the ED90 value in irrigated plants. The ED90 of sulfosulfuron to reduce the total dry mass of irrigated and water-stressed S. arvensis was 1022.4 and 1862.9 g ai ha−1, respectively. Water stress alleviated chlorophyll decline in herbicide-treated H. spontaneum, but induced chlorophyll degradation in S. arvensis and decreased Fv/Fm in both species. The results suggested that higher doses of sulfosulfuron are recommended for use in arid conditions to effectively manage weeds, particularly those exhibiting reduced sensitivity to the herbicide.