Regulatory effects of fertilization on root morphology and needle physiological characteristics of Pinus armandii Franch. container seedlings

This study explored the growth, root morphology, and physiological characteristics of Pinus armandii Franch. container seedlings under different fertilization treatments to reveal the regulatory effects of fertilization on seedling quality. The P. armandii container seedlings were grown under four fertilizer rates (100, 200, 300, and 400 mg N/seedling) with either conventional or exponential fertilization, with no fertilization serving as a control. The effects of fertilization on growth, root morphology, and physiological characteristics were then analyzed. Results showed that under both conventional and exponential fertilization, seedling height, root collar diameter, biomass, root length, root surface area, and root volume all initially increased and then decreased, while root tissue density and soluble sugar and malondialdehyde contents initially decreased and then increased with the increase in fertilizer application rates. Furthermore, as fertilizer application increased, specific root length and specific surface area decreased while root average diameter and free proline and soluble protein contents increased. Most indices were higher under exponential fertilization than conventional fertilization at the same fertilizer rate. The E300 treatment (exponential fertilization at 300 mg N per plant) yielded the highest comprehensive score. In conclusion, rational fertilization promoted seedling growth and root development and improved the physiology of P. armandii container seedlings, with the optimal fertilization treatment being exponential fertlization at 300 mg N per plant.