光照和氮磷供应比对3种典型乔木幼苗光合生理特性的影响

目的 研究不同生态型树种光合生理特征对光照和养分供应的响应规律,为人工林高效培育提供科学依据。 方法 以麻栎、闽楠及木荷幼苗为研究对象,设置2种光环境（自然全光照,45%全光照）和3种施肥氮磷供应比（N:P=5、N:P=15、N:P=45）,测定光合荧光参数以及苗高、地径的变化,研究植物光合生理参数在异质环境中的变化特征,分析林木生长与光合生理参数的关系。 结果 （1）与全光照处理相比,遮阴降低了麻栎的光饱和点（LSP）和最大净光合速率（Pnmax）,增加了木荷的Pnmax,而闽楠Pnmax没有显著变化。2种光照处理下,施肥均增加了闽楠和木荷LSP和光补偿点（LCP）,但施肥对遮阴下麻栎LSP和LCP影响较小。（2）遮阴显著降低了麻栎、闽楠和木荷调节性能量耗散的量子产量Y （NPQ）,显著增加了非调节性能量耗散的量子产量 Y （NO）。在全光照处理下,施肥普遍增加了麻栎、闽楠和木荷PSⅡ实际光合量子产量Y（II）和ETR,降低了Y（NPQ）;在遮阴处理下,施肥显著增加闽楠Y（II）和ETR,而麻栎Y（II）和ETR在氮磷供应比为5时显著增加,木荷Y（II）和ETR在氮磷供应比为15时显著增加。（3）相对于全光照处理,遮阴显著增加麻栎、闽楠和木荷叶绿素a、叶绿素b、叶绿素a + b及类胡萝卜素含量,2种光照处理下施肥显著增加麻栎、木荷和闽楠（仅全光照处理）的光合色素含量。（4）无论在光照还是遮阴条件下,施肥普遍增加了麻栎、闽楠和木荷苗高和地径相对增长率,3个树种生长与光合色素含量均正相关。 结论 麻栎、闽楠和木荷叶片光合生理特征和生长受光照和施肥交互作用影响,不同光照强度下氮磷施肥对林木促生效应大小受氮磷供应比和树种影响。

Effects of Light and N:P Ratio on Photosynthetic Characteristics in Seedlings of Three Typical Tree Species

Objective To study the response of photosynthetic characteristics of different ecological tree species to light and nutrient supply for providing a scientific basis for plantation cultivation. Method The seedlings of Quercus acutissima, Phoebe bournei, and Schima superba were used. This study included two light intensities (natural full light and 45% full light) and three N:P ratios (N:P=5, N:P=15, N:P=45). We measured the changes of Photosynthetic fluorescence parameters, and seedlings’ height, seedlings’ ground diameter to study the changes of plant photosynthetic characteristics in different environments, and analyze the relationship between seedling growth and photosynthetic parameters. Result (1) Compared with the full light treatment, the shading treatment decreased the light saturation point (LSP) and the maximum net photosynthetic rate (Pnmax) of Q. acutissima, and increased the Pnmax of S. superba. but had no significant effect on Pnmax of P. bournei. Under the two light treatments, fertilization increased the LSP and light compensation point (LCP) of P. bournei and S. superba, but the effects of fertilization on the shading LSP and LCP of Q. acutissima were less. (2) Shading significantly reduced the quantum yield of regulated energy dissipation of PSⅡ [Y(NPQ) ] of Q. acutissima, P. bournei and S. superba, and significantly increased the quantum yield of non-regulated energy dissipation of PSⅡ [ Y (NO) ]. Under the full light treatments, fertilization generally increased the effective quantum yield of PSⅡ [Y(II) ] and ETR of Q. acutissima, P. bournei and S. superba, but decreased Y(NPQ) . Under the shading treatments, fertilization significantly increased Y(II) and ETR of P. bournei, while Y(II) and ETR of Q. acutissima increased significantly when the N:P supply ratio was 5. Y(II) and ETR of S. superba increased significantly when the N:P supply ratio was 15. (3) Compared with the full light treatment, shading significantly increased the contents of chlorophyll a, chlorophyll b, chlorophyll a + b and carotenoid of Q. acutissima, P. bournei and S. superba. Under the two light treatments, fertilization significantly increased the photosynthetic pigment content of Q. acutissima, S. superba and P. bournei (only full light treatment). (4) Regardless of light or shading, fertilization generally increased the relative growth rates of seedling’s height and ground diameter of the three tree species, and there was a positive correlation between the growth and photosynthetic pigment. Conclusion Photosynthetic characteristics and growth of Q. acutissima, P. bournei and S. superba are affected by the interaction of light and fertilization. The effect of nitrogen and phosphorus fertilization on seedling growth under different light intensities depends on nitrogen and phosphorus supply ratio and tree species.