Effects of arbuscular mycorrhizal fungi on the nitrogen distribution in endangered Torreya jackii under nitrogen limitation

摘要

Rhizophagus irregularis was inoculated into sterilized soil to investigate its impact on the distribution ratio of leaf nitrogen in cell wall proteins, cell membrane proteins, water-soluble proteins, and photosynthetic systems which includes the carboxylation system (P-C), energy metabolism (P-B), and light-harvesting system in the endangered species Torreya jackii. The results showed that R. irregularis reduced the specific leaf weight and the distribution ratio of nitrogen in cell wall proteins in the leaves of T jackii, whereas it enhanced the distribution ratio of nitrogen in cell membrane proteins and water-soluble proteins. R. irregularis enabled more nitrogen uptake for growth by decreasing the distribution of nitrogen to the structural substances. At low-nitrogen levels, inoculation with R. irregularis improved the plant height (18.78 similar to 36.04%), shoot dry weight (50.53 similar to 64.33%), total dry weight (42.86 similar to 52.82%), maximal net photosynthetic rate (P-max) (16.83 similar to 20.11%), photosynthetic nitrogen use efficiency (PNUE) (40.01 similar to 43.14%), P-C (33.56 similar to 38.59%) and P-B (29.08 similar to 34.02%). However, it did not substantially affect the leaf nitrogen content per unit area or the leaf nitrogen content per unit mass. Moreover, P-max exhibited a significant positive correlation with P-C and P-B , and all three parameters showed a significant positive correlation with the PNUE, thereby revealing that R. irregularis increased the photosynthetic capacity and PNUE of T. jackii through boosting P-C and P-B.