Seasonal variations in secondary wall components of Styrax tonkinensis seedlings and their responses to nitrogen nutrition

<bold>Objective</bold> This study aims to explore the effects of different nitrogen concentrations on the contents of the main components of the secondary wall（lignin，cellulose，and hemicellulose）in <italic>Styrax tonkinensis</italic> seedlings，thus providing a theoretical basis for regulating wood quality through fertilization and enhancing its utilization value as a pulpwood. <bold>Method</bold> Three-year-old <italic>Styrax tonkinensis</italic> seedlings were used as testing materials，with urea as the nitrogen source.Four nitrogen fertilizer concentrations（N1：1.5 g/plant，N2：3 g/plant，N3：6 g/plant，N4：9 g/plant）and a control（CK）were set up.Fertilization was conducted in several installments from June to September.The contents of lignin，cellulose，and hemicellulose in the roots，stems，and leaves of the seedlings during the growth process were determined，and the effects of different nitrogen concentrations on the secondary wall components of <italic>Styrax tonkinensis</italic> seedlings were analyzed. <bold>Result</bold> The contents of lignin，cellulose，and hemicellulose in the roots，stems，and leaves of <italic>Styrax tonkinensis</italic> seedlings exhibited highly significant seasonal variations.The lignin content in roots，stems，and leaves followed a consistent trend with the changing of seasons，initially increasing before decreasing.Significant differences in lignin content were observed among different organs，ranked as root &gt; stem &gt; leaf.The seasonal variation in cellulose content in stems showed an upward-downward-upward trend，while in roots，it first decreased and then increased，both peaking on December 15.In contrast，the trend in leaves was opposite to that in roots.The hemicellulose content in stems and roots gradually increased，reaching its maximum on December 15，whereas in leaves，it first rose and then declined，peaking on June 15.Nitrogen fertilization significantly influenced the content of major secondary wall components in different organs of <italic>Styrax tonkinensis</italic>.Across the four sampling periods，the lignin content in various organs displayed an initial decrease followed by an increase.In the latter three sampling periods，the lignin content in stems under the N1 treatment was significantly higher than that of the control（CK），peaking on September 15.Among the four sampling periods，cellulose content of the N1 treatment was the highest in different organs.Hemicellulose content exhibited an initial rise followed by a decline over time.In the latter three sampling periods，cellulose content in stems under the N1 treatment showed an increasing trend.On September 15，as nitrogen application rates increased，the hemicellulose content in roots，stems，and leaves also increased. <bold>Conclusion</bold> The secondary wall composition of <italic>Styrax tonkinensis</italic> is co-regulated by nitrogen concentration and growth stage.For pulpwood production，applying a low nitrogen rate（N1）in the early stage（June–July）can optimize cellulose synthesis while lignin content remains relatively low.Subsequently，moderately increasing nitrogen fertilization（N4）in the later stage（August–September）helps enhance hemicellulose content.This approach offers potential benefits for reducing pulping energy consumption and improving pulp yield.