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近年来大气氮(N)沉降的增加,导致森林土壤中有效N含量增加、N:P发生改变,研究N沉降对低磷(P)胁迫下林木根系分泌和P效率的影响具有重要意义。该文以马尾松(Pinus massoniana)家系作为试验材料,设置模拟N沉降与同质低P(介质表层与深层均缺P)、异质低P(介质表层P丰富、深层缺P)耦合的二年生盆栽实验,系统研究了模拟N沉降对低P胁迫下马尾松根系分泌性酸性磷酸酶(APase)活性、有机酸分泌以及P效率的影响。结果表明:(1)同质低P和异质低P下,模拟N沉降均显著提高了植株N:P化学计量比、增加了P素的相对匮乏程度,从而诱导根系增加了APase和有机酸的分泌,而同质低P比异质低P下增加幅度更大,其中有机酸分泌均与马尾松生长呈正相关关系,而APase活性与P效率相关性较小;(2)同质低P下,N沉降虽然增加了根系分泌,但未提高马尾松P素吸收和生长量,其原因在于,同质低P下植株N:P过高,因而植株对N沉降敏感性低;在异质低P下,植株表现为N、P共同限制,因而对N敏感性较高,N沉降增加了根系分泌,同时提高了N和P吸收效率、增加了生物量;(3)马尾松根系分泌对模拟N沉降的响应存在较大的家系差异。同质低P下,家系71×20的有机酸分泌和生物量对N沉降的响应幅度较大;异质低P下,家系36×29、71×20和73×23对N沉降的响应幅度较大。
In recent years, the increase of atmospheric nitrogen (N) deposition leads to the increase of available N and the N: P in forest soils. It is of great significance to study the effect of N deposition on the root exudation and P efficiency under low phosphorus (P) stress. In this study, Pinus massoniana pedigree was used as the experimental material to set up a biennial model with simulated N deposition and coupling of low P (medium and deep) and heterogeneous low P (medium P and deep) Pot experiments were conducted to study the effects of simulated N deposition on the activities of APSEase, organic acid secretion and P efficiency in Pinus massoniana seedlings under low P stress. The results showed that: (1) Simulated N deposition significantly increased plant N: P stoichiometry and increased the relative scarcity of P, which induced the increase of APase and organic acids , While the increase of homozygote P was greater than that of heterogeneity P, the organic acid secretion positively correlated with the growth of Pinus massoniana, while the correlation between APase activity and P efficiency was less; (2) Under the same conditions, the N sinking increased the root exudation, but did not increase the P uptake and growth of Pinus massoniana. The reason is that N: P was too high in plants with low homoplasia, and therefore the plants were less susceptible to N deposition. Under low P, the plants showed the common limitation of N and P, which was more sensitive to N. N deposition increased the root exudation, increased N and P absorption efficiency and increased the biomass. (3) The root exudation of Pinus massoniana There was a large pedigree difference in the response of simulated N subsidence. Under the same low P, the response of 71 × 20 organic acid secretion and biomass to N subsidence was greater; at heterogeneous low P, the response of 36 × 29, 71 × 20 and 73 × 23 to N subsidence Larger.