Change in root morphology, growth, and P transfer: Does foliar P application restrain root P-foraging behavior of Cunninghamia lanceolata seedlings in P-deficient environments?

Although foliar phosphorus application (FPA) is a fertilization method that can rapidly supplement nutrient elements in plants, it remains unclear whether it significantly affects the response strategy of roots under environmental stress. In this study, changes in plant growth, biomass allocation, and P use efficiency (PUE) of Chinese fir in different P environments were analyzed by FPA and root P application (RPA) treatments. The effects of FPA on P-foraging behavior of Chinese fir root system in P-deficient environment were then discussed. The root biomass with RPA was more significant at 0.03–0.25 mmol·L⁻¹ P concentrations than that with FPA; however, the PUE was significantly reduced by 28.89–29.41 %. With an increase in the P application concentration, under the effect of FPA, the Chinese fir roots mainly reduced root proliferation by decreasing the tip number, surface area and volume but increasing in diameter, as well as the PUE of root, aboveground. As a result, the entire plant was improved. However, the degree of morphological adjustment of the root system was lower than that under RPA. In summary, both FPA and RPA can alleviate P starvation in Chinese fir to a certain extent, thereby improving PUE. Compared with RPA, FPA had a more significant impact on the behavior of Chinese fir roots in sensing and responding to soil P content, and the roots could more quickly sense changes in P content in the body. This mechanism provides valuable insights into the root response strategies of plants in P-deficient environments.