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采用二因素三水平法设计模拟氮(N)、硫(S)沉降的盆栽试验,以Na2SO4为硫源、46%CO(NH2)2为氮源,其中氮沉降梯度为N1(0 kg hm-2 a-1)、N2(50 kg hm-2 a-1)、N3(100 kg hm-2 a-1),硫沉降梯度为S1(0 kg hm-2 a-1)、S2(15kg hm-2 a-1)、S3(30 kg hm-2 a-1).模拟试验6个月后,测定尾巨桉(Eucalyptus urophylla×Eucalyptus grandis)和杉木(Cunninghamia lanceolata)幼苗的SPAD值、可溶性蛋白含量、净光合速率(Pn)和叶绿素荧光参数,分析探讨氮、硫沉降处理下两树种幼苗光合特性的响应机制.结果表明:与空白对照组相比,单一中氮沉降显著促进两树种幼苗Pn的上升(P<0.05),且单一高氮沉降显著促进杉木幼苗可溶性蛋白含量的上升(P<0.05),表明单一氮处理在一定程度上提高了两树种幼苗的光合能力.尾巨桉幼苗各光合指标受单一硫沉降胁迫的影响较杉木幼苗更为显著,前者的SPAD值和可溶性蛋白含量在中硫处理下均显著下降(P<0.05),Pn反之;而后者仅SPAD值在中、高硫处理下显著上升(P<0.05).氮、硫复合沉降下,尾巨桉幼苗各项指标未见明显变化(P>0.05);杉木幼苗仅中氮高硫组的SPAD值和高氮高硫组的可溶性蛋白含量显著上升(P<0.05).综上,与单一氮、硫沉降相比,氮、硫复合沉降的交互效应并未显著增强两树种幼苗的光合特性,但两树种幼苗间对模拟氮、硫沉降的响应和耐受机制存在差异.
A pot experiment was conducted to simulate the deposition of nitrogen (N) and sulfur (S) using two factors and three levels. Na2SO4 was used as the sulfur source and 46% CO (NH2) 2 was used as the nitrogen source. The nitrogen deposition gradient was N1 N2 (50 kg hm-2 a-1), N3 (100 kg hm-2 a-1), sulfur deposition gradients S1 (0 kg hm-2 a-1), S2 -2 a-1) and S3 (30 kg hm-2 a-1) .After 6 months of simulated test, the SPAD value and the content of soluble protein in Eucalyptus urophylla × Eucalyptus grandis and Cunninghamia lanceolata seedlings were determined. Content, photosynthetic rate (Pn) and chlorophyll fluorescence parameters of the two tree seedlings under nitrogen and sulfur deposition were investigated.The results showed that the single medium N deposition significantly promoted the photosynthetic characteristics of two tree seedlings Pn (P <0.05), and single high N deposition significantly increased the soluble protein content of Chinese fir seedlings (P <0.05), indicating that single N treatment increased the photosynthetic capacity of two seedlings in a certain extent. Photosynthetic index was more affected by single sulfur deposition than that of Chinese fir seedlings. The SPAD value and soluble protein content of the former decreased significantly (P <0.05) and P (P <0.05), while SPAD values of the latter only increased significantly under medium and high sulfur treatments (P <0.05). Under the composite deposition of nitrogen and sulfur, the indexes of seedlings of E. urophylla had no significant changes (P> 0.05) The SPAD value and the content of soluble protein in high-nitrogen and high-sulfur group increased significantly (P <0.05) .In conclusion, the interaction effect of nitrogen and sulfur deposition did not significantly increase compared with single nitrogen and sulfur deposition The photosynthetic characteristics of seedlings of two species were different, but there was a difference in the response and tolerance mechanisms between the seedlings of two species to the simulated nitrogen and sulfur deposition.