Abstract Little is known regarding changes in cell wall structural molecules (lignin, cellulose and hemicellulose) as plant roots decompose, despite their importance for soil organic matter (OM) formation. The objectives of this study were to quantify changes in root composition during 270 d incubations of ten important grain and forage crops utilizing forage fiber analysis and to characterize the changes in cell wall composition and structure using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Large, species-dependent variation was observed in the extent of root tissue decomposition over time, ranging from 82.5% of initial mass for alfalfa to 21.5% for switchgrass. Fiber analysis revealed that initial rapid decomposition increased lignin concentration and cellulose concentration while hemicellulose declined, whereas all three moieties degraded proportionally thereafter. Similar trends were found in the ratios between the DRIFTS diagnostic peaks for lignin, cellulose and the carbonyls of hemicellulose and wax components. Spectra illustrated changes during decomposition, particularly in more extensively decomposed roots. Features potentially indicative of suberin preservation were found in the region between 2800 cm−1 and 3000 cm−1. Examination of the region between 1000 cm−1 and 1300 cm−1 revealed possible change in hemicellulose structure. The results illustrate the effect of differences in cell wall composition and structure during root decomposition and expand understanding of the role of roots in soil OM dynamics. Variability in root degradation and change in cell wall composition among species demonstrate that characterization of a broad range of individual species is necessary to predict root contributions to soil C.

中文翻译：

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重要农作物和牧草物种延长分解过程中植物根细胞壁结构分子的降解变化

摘要：尽管植物根系分解时细胞壁结构分子（木质素、纤维素和半纤维素）对土壤有机质 (OM) 的形成很重要，但它们的变化鲜为人知。本研究的目的是利用草料纤维分析量化 10 种重要谷物和草料作物在 270 天孵化过程中根部成分的变化，并利用漫反射红外傅里叶变换光谱 (DRIFTS) 表征细胞壁成分和结构的变化。随着时间的推移，在根组织分解的程度中观察到了较大的物种依赖性变化，范围从紫花苜蓿初始质量的 82.5% 到柳枝稷的 21.5%。纤维分析表明，初始快速分解增加了木质素浓度和纤维素浓度，而半纤维素则下降，而此后所有三个部分都成比例地降解。在木质素、纤维素和半纤维素和蜡组分的羰基化合物的 DRIFTS 诊断峰之间的比率中发现了类似的趋势。光谱说明了分解过程中的变化，特别是在更广泛分解的根中。在 2800 cm-1 和 3000 cm-1 之间的区域发现了可能表明木栓质保存的特征。检查 1000 cm-1 和 1300 cm-1 之间的区域显示半纤维素结构可能发生变化。结果说明了根分解过程中细胞壁组成和结构差异的影响，并扩大了对根在土壤有机质动力学中作用的理解。