The effects of carbon and nitrogen co-application on photosynthetic characteristics, quality, and carbon-nitrogen metabolism of Dendrobium officinale

Adequate carbon and nitrogen sources can promote biomass accumulation in plants. To investigate the effects of combined application of carbon and nitrogen elements at different concentrations on Dendrobium officinale photosynthetic characteristics, quality and carbon and nitrogen metabolism, two-year-old red-stemmed D. officinale seedlings was treated with solutions of α-ketoglutaric acid (KG) and Urea ammonium nitrate (AN) at different mass percentage concentrations. To measure photosynthetic parameters, monosaccharide content in stems, polysaccharide content, iron and zinc content, activity of carbon metabolism enzymes, and metabolomics. Results showed that carbon and nitrogen co-application improved its photosynthetic performance and quality. After 10 wk of treatment, the contents of soluble sugar, iron, and zinc in D. officinale stems followed the order: 1AN < CK < 20KG < 0.4AN/20KG. This order was consistent with the changes in the activities of carbon metabolism enzyme . In treatments with no nitrogen, low nitrogen, and medium nitrogen levels, the content of photosynthetic pigments and the net photosynthetic rate in D. officinale increased over time. However, under high nitrogen conditions, showed a contrary trend of change . Based on preliminary results, optimal treatment groups for single carbon, single nitrogen, and carbon and nitrogen co-application were selected for metabolomic analysis. The 0.4AN/20KG treatment group showed significantly better nitrogen metabolism pathway and carbon compound contents than the 20KG and 0.4AN treatment groups, enhancing accumulation of metabolites in D. officinale. In conclusion, the 0.4AN/20KG carbon and nitrogen co-application treatment enhanced photosynthetic characteristics of D. officinale, promoted carbon-nitrogen metabolism cycling, and improved quality.