Phlomoides rotata adapts to low-nitrogen environments by promoting root growth and increasing root organic acid exudate

Nitrogen (N) is one of the three major elements required for plant growth and development. It is of great significance to study the effects of different nitrogen application levels on the growth and root exudates of Phlomoides rotata, and can provide a theoretical basis for its scientific application of fertilizer to increase production. In this study, Phlomoides rotata were grown under different nitrogen conditions for two months. Soil and plant analyzer development (SPAD) values, bioaccumulation, root morphology, root exudate composition, nitrogen metabolism enzyme and antioxidant enzyme activity were evaluated. The results showed that compared with CK (no N fertilizer), N2 (CO(NH₂)₂ 80 mg/kg) and N3 (CO(NH₂)₂ 160 mg/kg) through significantly improved the activities of nitrogen metabolism enzyme nitrite reductase (NiR), glutamate dehydrogenase (GDH) and glutamine synthetase (GS), enhanced the nitrogen metabolism process, and increased the accumulation of plant soluble sugars (SS) and soluble protein (SP), thus improving Phlomoides rotata biomass yield. After 60 days of treatment, low nitrogen (N₁, CO(NH₂)₂ 40 mg/kg) increased root length, root volume, root surface area, average root diameter, significantly increased the diversity of organic acids in root exudates, and enhanced the activity of antioxidant enzymes to adapt the nitrogen deficiency environment. This study can provide new ideas for understanding the mechanism of nitrogen tolerance in Phlomoides rotata and developing scientific fertilization management strategies for plateau plants and medicinal plants.