Effects of combined application of selenium and polyaspartic acid-based water-retaining agent on the growth, drought resistance, yield and quality of tomato under drought stress

Drought stress severely restricts the growth, development, yield, and fruit quality of tomato ( Solanum lycopersicum L.). Selenium (Se) and polyaspartic acid-based water-retaining agent (PASP) can enhance crop growth and development, but the effects of their co-application on tomato drought tolerance remain unclear. This study explored the effects of combined root application of Se and PASP on drought tolerance in tomato. The tomato plants were treated with 25 μM Se and 0.3 % PASP individually or in combination on drought-stressed tomato. After 15 days of treatment, Se and PASP effectively elevated leaf photosynthetic rate, reduced malondialdehyde (MDA), soluble sugar, proline and excessive reactive oxygen species (ROS) accumulation, and the combined treatment exerted markedly improved effects on alleviating growth inhibition and improving water use efficiency. In terms of fruit quality, the combined treatment significantly increased the contents of soluble solids, flavonoids, total free amino acids, and β-carotene under drought conditions. Under non-stress conditions, however, the co-application effectively improved multiple fruit nutritional quality indicators, including vitamin C, total phenols, flavonoids, amino acids, and lycopene. Additionally, the combined treatment substantially increased single-plant yield under drought stress. Collectively, the co-application of Se and PASP enhances tomato drought tolerance and water use efficiency by improving photosynthetic performance, strengthening antioxidant and osmotic regulation capacity, and maintaining cell membrane stability, while effectively improving tomato fruit quality and yield. This study provides a theoretical basis and practical reference for optimizing drought-resistant cultivation techniques for tomato in water-deficient regions.