Study on differences in responses of Camellia oleifera seedlings to phosphorus levels under different nitrogen levels

<bold>Objective</bold> Nitrogen and phosphorus in soil are necessary for the growth of <italic>Camellia oleifera</italic>，and their available content directly affects the growth and development of <italic>Camellia oleifera</italic>. <italic>Camellia oleifera</italic> is a woody oil tree growing in the south，which has a certain adaptability to low soil phosphorus conditions.In the nutrient management of seedlings，the method of combined application of nitrogen（N）and phosphorus（P）is often used.However，the interaction between nitrogen and phosphorus on Camellia oleifera remains unclear；therefore，exploring the phosphorus utilization strategy of Camellia oleifera under different nitrogen levels is crucial for seedling cultivation. <bold>Method</bold> In this study，Changlin 53（CL53），the main cultivar of oil tea in Jiangxi，was used as the experimental material.Under the conditions of no nitrogen N0（0 mmol/L）and nitrogen N1（15 mmol/L），Four phosphorus levels ［（P0（0 mmol/L），P1（0.4 mmol/L），P2（0.8 mmol/L），P3（1.6 mmol/L）］were set to study the growth and physiological response of <italic>Camellia oleifera</italic> seedlings to four phosphorus application levels，and the utilization strategy of <italic>Camellia oleifera</italic> seedlings was discussed. <bold>Result</bold> There was a synergistic effect between N and P，and N application reduced the P demand of <italic>Camellia oleifera</italic> seedlings in the critical growth period.N0P3 and N1P2 treatments significantly promoted the plant height and ground diameter growth of <italic>Camellia oleifera</italic> seedlings，and the plant height was 15.00% and 16.50% higher than other treatments，respectively.The ground diameter is more than 5% and 7% higher than other treatments，respectively.From the physiological point of view，it significantly promoted the accumulation of photosynthetic pigment content，which was more than 15.63% and 6.25% higher than other treatments，respectively.N0P2 and N1P0 treatments showed better root growth，which was similar to the change of ACP enzyme activity.Single application of phosphorus or nitrogen can affect the normal physiology of <italic>Camellia oleifera</italic> and induce significantly enhanced enzyme activity.The correlation analysis between growth and physiology of <italic>camellia oleifera</italic> showed that plant height was positively correlated with photosynthetic pigment.The total root length，total root surface area and root volume were positively correlated with ACP activity. <bold>Conclusion</bold> After the addition of different nitrogen（N）and phosphorus（P）nutrients，the seedling height，ground diameter，and root system of CL53 seedlings showed differences to varying degrees，and these differences are physiological.The growth and photosynthesis of <italic>Camelia</italic><italic>oleifera</italic> seedlings can be promoted by increasing the P concentration properly without N application，and the appropriate P concentration should be provided after N application.This study can provide reference for phosphorus nutrient management of <italic>Camellia oleifera</italic>.