Abstract

Humic substances are an important soil quality indicator, influencing its physical-chemical and biological characteristics while directly affecting plant growth, through their biostimulant activity. To elucidate the role of humic substances in seedlings acclimation it’s important to establish a relationship among the origin, the structural composition and their biological activity. The aim of the present paper is to characterize the soluble humic fractions extracted from soils of the Brazilian Cerrado biome with different levels of preservation, and to verify their biological activity on seedlings of the pioneer Cerrado native species Enterolobium contortisiliquum (Vell.) Morong. Humic and fulvic acids were isolated from preserved and degraded Cerrado areas. Humic compounds were characterized assessing total acidity, UV-VIS and IR spectra. Humic substances bioactivity was evaluated on E. contortisiliquum seedlings grown in Leonard pots, supplied with nutrient solution added with the optimal concentrations of humic and fulvic acids and their mix. Seedlings root structure, antioxidant enzymes activity and photosynthetic pigments contents were evaluated. The humic substances showed different chemical characteristics and bioactivity depending on sampling area. Mixed humic and fulvic acids showed higher efficacy, especially those coming from the preserved area. It is noteworthy that A) the type of management influences humic fraction chemical structure, well reflected in their biological activity B) E. contortisiliquum, shows a better response to humic substances coming from a well-established and stable canopy.

中文翻译：

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从保存和降解的巴西 Cerrado 生物群落土壤中提取的腐植酸和黄腐酸的结构表征和生物活性

摘要

腐殖质是重要的土壤质量指标，通过其生物刺激活性影响其理化和生物学特性，同时直接影响植物生长。为了阐明腐殖质在幼苗驯化中的作用，建立其起源、结构组成及其生物活性之间的关系非常重要。本论文的目的是表征从巴西 Cerrado 生物群系土壤中提取的具有不同保存水平的可溶性腐殖质部分，并验证它们对先驱 Cerrado 本土物种Enterolobium contortisiliquum幼苗的生物活性(Vell.) 莫龙。从保存和退化的塞拉多地区分离出腐殖酸和黄腐酸。腐殖质化合物的特征在于评估总酸度、UV-VIS 和 IR 光谱。在E. contortisiliquum上评估腐殖质的生物活性在 Leonard 花盆中生长的幼苗，提供添加了最佳浓度的腐殖酸和富里酸及其混合物的营养液。对幼苗根系结构、抗氧化酶活性和光合色素含量进行了评价。腐殖质因取样区域不同而表现出不同的化学特性和生物活性。混合腐殖酸和富里酸显示出更高的功效，尤其是来自保护区的那些。值得注意的是，A) 管理类型会影响腐殖质部分的化学结构，这很好地反映在它们的生物活性中 B) E. contortisiliquum对来自完善和稳定的树冠的腐殖质物质表现出更好的反应。