不同林分及农田土壤中球囊霉素蛋白组成特征差异研究

Compositional variation of glomalin-related soil protein in different forest stands and farmland

球囊霉素相关土壤蛋白（GRSP）是由丛枝菌根真菌产生的一种不易溶于水的糖蛋白,对GRSP化学结构特征认知的匮乏,很大程度上限制了GRSP的生态学地位及其应用前景。本文选取东北林业大学实验林场5种林分及其毗邻农田为研究对象,通过多种技术手段,来揭示GRSP的特征及其在不同林型和农田中的差异。研究发现GRSP含有O—H和N—H伸缩振动带、C—H伸缩振动带、C=O和COO—伸缩振动带、COO—伸缩振动带和C—H弯曲收缩带、C—O和Si—O—Si伸缩振动带5种官能团。紫外吸收峰位置在225~248 nm之间,OD值在0.9~2.0之间。X射线衍射结果显示GRSP含有石英、蒙脱石、伊利石、斜长石、伊利石蒙脱石混层和未知的a物质及b物质等多种矿物质,相对结晶度均较低,平均晶粒尺寸分别为25.83、17.93、14.50、21.45、28.45、28.10和17.40 nm。此外,通过X光电子能谱发现GRSP含有C1s、Al2p、O1s、Si2p、P2p、Ca2p、K2p、N1s、Fe2p、Mg1s和Na1s 11种元素,平均所占百分比为28.9%、7.0%、43.4%、9.8%、0.4%、1.0%、0.6%、1.4%、2.1%、0.7%和7.8%。GRSP的化学特征在不同林型及农田中也存在着一定的差异,其中官能团差异最大的是蒙古栎和白桦林的C—H伸缩振动带（5.5倍）,差异最小的是水曲柳和白桦林的O—H和N—H伸缩振动带（1.3倍）,胡桃楸林GRSP的OD值最大。GRSP矿物质种类也有所不同,其中只有水曲柳和蒙古栎林中包含斜长石、伊利石蒙脱石混层、a物质、b物质,其余矿物质在所有林型和农田的GRSP中均有发现。石英的晶粒尺寸差异最大,达到5.2倍,最小的为斜长石仅相差17%。落叶松林中的蒙脱石相对结晶度是水曲柳林的5.1倍,而b物质在水曲柳林和蒙古栎林中的相对结晶度仅相差4%。同样,C1s、O1s、Si2p、N1s和Na1s等元素在所有林型和农田中都可被检测到,其中GRSP各元素在不同林型及农田中的差异在1.1~31.6倍之间。我们的研究结果显示不同植被类型中GRSP组成特征可能具有很大的差异,同时GRSP中含有不同土壤矿物说明土壤组成对GRSP也有一定影响,本文对GRSP的化学结构特征的客观揭示,有助于探索GRSP对农田及森林土壤生态功能影响方面的深层机制。

Glomalin-related soil protein（ GRSP）, a glycoprotein produced by the hyphae of arbuscular mycorrhizal fungi,is well known for its significant ecological role in soil function,while lack of cognition of GRSP chemical structural characteristics has largely restricted the ecological status and application prospect of GRSP. In this study,five tree species and adjacent farmland have been investigated to uncover the structural characteristic of GRSP and the inter-specific differences through a variety of technical methods. We found that GRSP contained five functional groups,i. e. O—H and N—H stretching,C—H stretching, C=O and COO— stretching,symmetric COO— stretching, C—H bending,C—O and Si—O—Si stretching. Ultraviolet spectrum showed that the peak wavelengh of GRSP was 225-248 nm and OD value was 0. 9-2. 0. XRD data showed that GRSP contained seven mineralsubstances（ quartz,montmorillonite,illite,plagioclase,illite montmorillonite mixed-layer,and two unrecognizable substances）,and their relative crystallinity was quite low with average grain size 25. 83,17. 93,14. 50,21. 45,28. 45,28. 10 and 17. 40 nm,respectively. Moreover,XPS data found 11 elements of C1 s,Al2p,O1 s,Si2p,P2 p,Ca2p,K2 p,N1s,Fe2 p,Mg1s and Na1 s in GRSP,and their average percentages were 28. 9%,7. 0%,43. 4%,9. 8%,0. 4%,1. 0%,0. 6%,1. 4%,2. 1%,0. 7% and 7. 8%,respectively. Tree species and farmland practices strongly affected GRSP composition.The biggest difference of function group was C—H stretching between Mongolian oak and birch（ 5. 5fold）,while the minimum difference was O—H and N—H stretching between Manchurian ash and birch（ 1. 3 fold）. Juglans mandshurica had the highest Uv-OD values. Mineral types of GRSP were also different. Manchurian ash（ Fraxinus mandshurica） and Mongolian oak（ Quercus mongolica） forests contained plagioclase,illite montmorillonite mixed-layer,and two unrecognizable substances,and more soil mineral substances were found in GRSP from other tree species and farmland. The 5. 2-fold difference of quartz grain size was found in different vegetations,while plagioclase had the minimum inter-species differences（ 17%）. Relative crystallinity of montmorillonite in larch plantation was 5. 1 fold higher than that in Manchurian ash,while very smaller differences in two unrecognizable substances（ 4%variation of b substance） were found between Manchurian ash and Mongolian oak forests. C1 s,O1s,Si2 p,N1s and Na1 s could be found in GRSP from all forests and farmland,and their variation was 1. 1-31. 6 fold. Our study confirms that GRSP composition varies greatly among different vegetational types,and soil minerals could also affect the composition owing to variable soil minerals in GRSP. Clarification of the influencing mechanism of GRSP through revealing the GRSP compositional characteristics in this study is helpful for restoring soil ecological functions of farmland and forest soils in this region.