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首页> 外文学位 >Total phenolics, condensed tannins, and nordihydroguaiaretic acid (NDGA) as potential allelopathic compounds in creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov.] and tarbush (Flourensia cernua DC) in the northern Chihuahuan Desert (New Mexico).
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Total phenolics, condensed tannins, and nordihydroguaiaretic acid (NDGA) as potential allelopathic compounds in creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov.] and tarbush (Flourensia cernua DC) in the northern Chihuahuan Desert (New Mexico).

机译：奇瓦瓦沙漠北部（新墨西哥州）和杂草油中总的酚类，缩合的单宁酸和去甲二氢愈创木酸（NDGA）作为潜在的化感化合物。 。

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摘要

Shrubs have replaced arid grasslands over large parts of the American southwest. Multiple mechanisms are proposed to explain this shift. One hypothesis invokes allelopathy as a mechanism for maintenance of shrub dominance in arid grasslands. This paper focuses on secondary compounds found within creosotebush and tarbush, their distribution, and possible losses from plant tissues through precipitation and leaf decay.; Total phenolics, condensed tannins and nordihydroguaiaretic acid (NDGA) were measured in nine categories of tissue. Total phenolic and condensed tannin concentrations were determined using colorimetric methods, NDGA content was determined with high performance liquid chromatography. Total phenolics were present throughout the plant with highest concentrations in leaves (36.2 mg/g), green stems (40.8 mg/g) and roots (mean for all root categories = 28.6 mg/g). Condensed tannins were in all tissues except larger stems (5 to 12 mm in diameter), with highest concentrations in flowers (1.7 mg/g), seeds (1.1 mg/g), and roots less than 5 mm in diameter (1.1 mg/g). Flowers, leaves, green stems, and small stems (5 mm in diameter) all contained NDGA, with highest concentrations in leaves (38.3 mg/g).; Stemflow, throughfall, and interspace precipitation collections were analyzed for total phenolics and nordihydroguaiaretic acid. Phenolics were found in throughfall and stemflow; 0.088 and 0.086 mg/ml for stemflow and 0.022 and 0.014 mg/ml for throughfall in two creosotebush morphotypes; 0.044 and 0.005 mg/ml for stemflow and throughfall, respectively, in tarbush. Nordihydroguaiaretic acid was not found in any precipitation samples.; Bags containing leaf litter were placed under shrubs. One set was placed on the surface, one set buried at 5 cm. They were then collected at intervals from 0 to 90 days. Sets 1 and 2 (creosotebush and tarbush, respectively) were in place from February to April. Set 3, creosotebush, was in place from April to July. Percent organic matter loss was 1.99% and 3.23% for Set 1 surface and buried samples, respectively, 2.31% and 2.49% for Set 2 surface and buried and 34.10% and 75.27% for Set 3 surface and buried, respectively. Set 1 lost total phenolics (surface 6%), NDGA (19% surface, 11% buried), and condensed tannins (53% surface and 44% buried). Set 2 had losses in total phenolics (27% surface, 38% buried) but concentration of condensed tannins increased slightly (1.41% surface, 1.47% buried). Set 3, spring creosote, lost total phenolics (13% surface, 48% buried), nordihydroguaiaretic acid (52% surface, 82% buried), and condensed tannins (55% surface, 68% buried).; This paper demonstrates the presence and distribution of secondary phenolic compounds in creosotebush and the movement of these compounds from production sites in creosotebush and tarbush to sites of possible allelopathic activity in soil. Phenolic compounds, other than NDGA, are moved from plant surfaces to soil through precipitation. Phenolic compounds are lost from leaf litter as the leaf decays. Within the duration of this study, this process is most effective from April through July. The fate of these compounds once in the soil, and their interactions with other plants, needs to be examined before a complete picture of possible allelopathic activity in creosotebush dominated systems in the northern Chihuahuan Desert can be presented.
机译：灌木已经取代了美国西南大部分地区的干旱草原。提出了多种机制来解释这种转变。一种假设将化感作用作为一种在干旱草原上维持灌木优势地位的机制。本文重点研究了在creosotebush和tarbush中发现的次生化合物，它们的分布以及由于降水和叶片腐烂而从植物组织中损失的可能性。在九种组织中测量了总酚类，缩合单宁和去甲二氢愈创木酸（NDGA）。用比色法测定总酚和缩合单宁的浓度，用高效液相色谱法测定NDGA的含量。整个植物中的总酚含量最高，分别在叶片（36.2 mg / g），绿色茎（40.8 mg / g）和根（所有根类别的平均值= 28.6 mg / g）中。除了较大的茎（直径5至12毫米）以外，所有组织中都含有浓缩的单宁，其中花朵（1.7毫克/克），种子（1.1毫克/克）和根部直径小于5毫米（1.1毫克/克）的浓度最高。 G）。花朵，叶子，绿色茎和小茎（直径<5毫米）都含有NDGA，叶子中的浓度最高（38.3 mg / g）。分析了干流，穿透水和空间降水的收集物中的总酚类和去甲二氢愈创木酸。在穿透和茎流中发现了酚类物质。两种creosotebush形态型的茎流分别为0.088和0.086 mg / ml，穿透量为0.022和0.014 mg / ml； Tarbush中的茎流和贯通滴分别为0.044和0.005 mg / ml。在任何沉淀样品中均未发现去甲双氢愈创木酸。将装有落叶的袋子放在灌木下。一组放置在表面上，一组埋在5厘米处。然后每隔0到90天收集一次。 1月和2组（分别为creosotebush和tarbush）在2月至4月间就位。第三组creosotebush于4月至7月间就位。组1的表面和掩埋样品的有机物损失百分比分别为1.99％和3.23％，组2的表面和掩埋样品分别为2.31％和2.49％，组3的表面和掩埋样品分别为34.10％和75.27％。组1损失了总酚类（表面6％），NDGA（表面19％，埋藏11％）和单宁浓缩（表面53％，埋藏44％）。组2的总酚含量降低（27％的表面，埋藏的38％），但单宁浓缩的浓度略有增加（1.41％的表面，埋藏的1.47％）。第3组，春季杂酚油，总酚损失（表面13％，埋藏48％），去氢二氢愈创木酸（52％表面，埋藏82％）和单宁浓缩（表面55％，埋藏68％）。本文说明了杂酚醛中次酚类化合物的存在和分布，以及这些化合物从杂酚醛和塔布灌木生产地向土壤中可能发生化感作用的位置的运动。除NDGA外，酚类化合物通过降水从植物表面移至土壤。随着叶片的腐烂，酚类化合物会从枯枝落叶中丢失。在本研究期间，此过程从4月到7月最为有效。这些化合物一旦进入土壤，其结局以及它们与其他植物的相互作用，需要先进行考察，然后才能完整地描述北部奇瓦瓦沙漠中杂居灌木为主的系统中可能的化感作用。

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