Seed treatments can enhance the tolerance of plants to abiotic stress. This study explored the effects of different seed treatment methods under drought stress on the growth and nutrient uptake of maize at the seedling stage, to provide a theoretical reference for maize cultivation with high yield, high efficiency and strong ecological adaptability.

A pot experiment was conducted, with five seed treatments, including control (CK), ultrasound (US), ultrasound+polysaccharide (US+OS), ultrasound+microorganism (US+B), and integrated technology (US+polysaccharide+microorganism, IPM). The agronomic traits, photosynthetic physiology, antioxidant enzyme activities, and nutrient uptake of maize at the seedling stage under different simulated drought stress conditions were investigated. Combining with the Mantel test and random forest, the potential relationships among the indicators affecting the nutrient uptake of maize were analyzed.

Compared with the CK, seed treatment significantly improved the plant height, leaf area, root length, root surface area, root volume and root diameter. These stimulative features were conducive to increasing the root dry weight by 69.23%-171.15% under light drought, 59.09%-218.18% under moderate drought, and 93.84%-264.52% under severe drought. Seed treatment significantly regulated the SPAD values and gas exchange parameters under drought stress, and increased the antioxidant enzyme activities, thereby improving the production of photosynthetic substances and the ability of osmotic regulation. The changes in physiological parameters directly promoted the functional metabolism of the plants, which was conducive to optimizing nutrient uptake of the leaves and roots. The US+B treatment achieved the greatest increase, with the nitrogen, phosphorus and potassium uptake of maize under drought stress increased by 31.59%-59.21% for leaves and 39.79%-82.35% for roots, 33.70%-69.94% for leaves and 51.66%-88.69% for roots, and 47.71%-78.17% for leaves and 57.59%-108.08% for roots, respectively. The Mantel test and the random forest analysis revealed that seed treatment obviously enhanced multiple growth parameters, thereby comprehensively improving the drought resistance of maize. The plant biomass, leaf area, and plant height were the key parameters affecting nutrient uptake.

Seed treatment could promote nutrient uptake and dry matter accumulation by optimizing the aboveground agronomic traits and root morphological characteristics of maize at the seedling stage under drought stress, and improving the photosynthetic physiological metabolism and antioxidant enzyme activities of leaves. The US+B treatment was expected to be a potential practice for enhancing the maize productivity in the dryland farmlands of the North China.