[Objectives] This paper focused on how nitrogen (N) deposition impacts growth of different clones ofPinus massoniana under phosphorus (P) deficient soils.The results could formulate the breeding strategy of P.massoniana under N deposition.[Methods] Taking five representative clones ofP.massoniana which were cultivated for one year from full-sib progenies as test materials,a pot experiment was conducted to investigate variations of growth,root morphology and N/P efficiency in response to simulated N deposition under both homogeneous low P stress (low P level in all soil layers) and heterogeneous low P stress (high P level in the topsoil and low P level in the bottom soil),respectively.[Results] 1) Large variations were detected in seedling height and dry matter accumulation among the P.massoniana clones under both the homogeneous and heterogeneous low P stress,moreover,significant clone and N interaction effect was detected in the homogeneous P deficiency.2) The adaptive mechanism to the N deposition was different under different types of low soil phosphorus.Under the homogeneous low-P condition,the adaptive responses of root length (RL),root surface area (RSA) and APase activity were present in clones with strong growth vigor by simulated N deposition such as "33-4" and "19-5",while it was not observed in clones with weak growth vigor.Meanwhile,the correlation between dry matter accumulation and APase activity was enhanced by the simulated N deposition.Under the heterogeneous low-P condition,RL and RSA were significantly improved by the simulated N deposition,while the special root length (SRL) was decreased,thus having the greater ability for nutrition absorption and having lower consumption.3) The P absorption efficiency (PAE) ofP.massoniana clones was significantly affected by the nitrogen deposition and showed a significant positive correlation with nitrogen absorption efficiency (NAE) under different N and P conditions (P ＜ 0.01).It indicated that the nitrogen deposition could increase the P mobilization and uptake ofP.massoniana clones under the P deficiency.In contrast,there was no significant effect on P use efficiency (PUE).4) The amplitudes of variations of dry matter accumulation,RL,RSA and APase were wider and the repeatability (R) of these traits exceeded 0.75 (P ＜ 0.05),respectively.[Conclusions] Our results revealed the possibility of selecting clones with optimal root morphology and active APase was increased for wood production ofP.massoniana under the low-P and high-N conditions.%[目的]剖析不同类型低磷胁迫下马尾松应对大气氮沉降的生长表现和适应机制,为在大气氮沉降背景下选育营养高效利用的马尾松速生优质新品种提供理论依据. [方法]以来自马尾松(Pinus massoniana)全同胞子代的5个优良无性系1年生扦插幼苗为材料,分别在同质低磷(介质表层与深层均缺磷)和异质低磷(介质表层磷丰富、深层缺磷)两种土壤磷素环境下设置两种浓度梯度的模拟氮沉降试验,以研究低磷胁迫下马尾松无性系苗木生长、根系发育及氮、磷效率对模拟氮沉降的响应差异和规律. [结果]1)不同类型低磷胁迫下马尾松苗高和干物质积累量均表现出显著的无性系变异,且在同质低磷下存在明显的无性系×氮交互效应(P＜0.05).2)马尾松无性系在不同类型低磷胁迫下应对氮沉降的适应机制有所差异.同质低磷、高氮环境下,33-4和19-5等生长势较强的无性系,其根系长度、根表面积以及根分泌的酸性磷酸酶活性显著高于生长势较弱的无性系,干物质积累量与酸性磷酸酶活性之间的相关性增强,表明根系可通过增加在土壤中的分布面积和提高酸性磷酸酶活性来应对高氮、低磷的外界环境;异质低磷下,生长势较强的无性系,其根系长度和表面积在高氮沉降下显著增加,但比根长反而显著下降,意味着根系在高氮下增加吸收面积的同时,降低自身内部消耗可能是马尾松高磷效率的重要生物学基础之一.3)马尾松无性系的磷吸收效率受氮沉降影响较大,在不同氮、磷水平下,其磷吸收效率与氮吸收效率均呈极显著正相关(P＜0.01),表明模拟氮沉降有利于马尾松无性系对土壤中磷素的活化吸收,但磷利用效率无显著差异.4)马尾松无性系的干物质积累量、根系长度、根表面积以及根分泌的酸性磷酸酶活性等指标的变幅较大,且无性系重复力均达到0.75(P＜0.05)以上,这为高氮、低磷环境下马尾松耐受型植株的选择提供了可能. [结论]以马尾松根系形态和根分泌的酸性磷酸酶活性变异为突破口,选育氮沉降下具有高磷效率的马尾松无性系将有利于遗传效益的提高.
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