Effects of sulfur on the growth and metabolism of sulfur and nitrogen in cabbage

Sulfur the fourth essential nutrient element required for plants after nitrogen, phosphorus and potassium plays a crucial physiological role in plant growth and stress resistance. This study aims to investigate the influence of sulfur on cabbage growth. In this study, cabbage was treated with sulfur-free Hoagland nutrient solution (control; − S; 0 mmol//L),or normal Hoagland nutrient solution(treatment; + S; 2 mmol/L). By measuring the cabbage growth index, antioxidant system, Nitrogen and Sulffur metabolism at different periods, this study explored S’s regulation mechanism for growth, nitrogen metabolism and sulfur metabolism. The results showed that sulfur could significantly promote the growth of cabbage. Under + S treatment, plant height and stem diameter were 15.1% and 15.6% higher than that of -S treatment, and the root dry matter distribution rate was the highest at the rosette and heading stage. 15.47% and 13.09% under + S treatment; 10.15% and 10.4% under -S treatment. Additionally, sulfur promoted photosynthesis, fluorescence, antioxidant enzyme system and glutathione cycle of cabbage. During the period when the Ci was the highest and the Pn reached its maximum, the Ci of + S treatment was 15% higher than that of -S treatment. We discovered that sulfur promoted both nitrogen and sulfur metabolism in cabbage, and + S treatment significantly increased the activities of ATP sulfase (ATPS) and APS reductase (APR) in cabbage. During the whole growth period of cabbage, + S treatment increased ATPS activity by 15.5%, 13.8%, 45.2% and 25.7%, respectively. To sum up, sulfur not only participates in the regulation of basal metabolism during cabbage growth and development but also plays a imperative role in key physiological processes such as activation of the antioxidant system, optimization of the photosynthetic efficiency, and synergistic metabolism of nitrogen and sulfur assimilation. This study provides a theoretical basis for a indepth understanding of the molecular mechanisms by which sulfur nutrition regulates crop growth and metabolic networks, and also lays an important foundation for the precision application of sulfur fertilizers and the optimization of crop sulfur nutrition management strategies.