|Estell, Richard - Rick|
Submitted to: Biochemical Systematics and Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2002
Publication Date: 11/1/2002
Citation: HYDER, P.W., FREDRICKSON, E.L., ESTELL, R.E., TELLEZ, M.R., GIBBENS, R.P. DISTRIBUTION AND CONCENTRATION OF TOTAL PHENOLICS, CONDENSED TANNINS AND NORDIHYDROGUAIARETIC ACID IN CREOSOTEBUSH (LARREA TRIDENTATA). BIOCHEMICAL SYSTEMATICS AND ECOLOGY. 2002. V. 30(10). P. 905-912.
Interpretive Summary: Creosote bush (Larrea tridentata)has expanded its geographical range during the last 100 years, resulting in replacement of arid grasslands by creosotebush and other shrubs. This transition results in a decline in the land's economic and ecological potential, affecting large regions of the U.S. and North America. As a result, the mechanisms responsible for this transition are a topic of great interest. The appearance of creosotebush in desert grasslands alters plant community structure and soil properties with the number of plant species and soil fertility declining. This study examined creosotebush chemistry for compounds that may be toxic to neighboring plants and important soil organisms. Presence of these compounds in soils surrounding creosotebush potentially inhibits establishment of grassland plants and gives creosotebush a competitive advantage. The first step in demonstrating that these chemical interactions occur is to verify the presence of compounds with potential toxic properties, which is the focus of this paper. We found significant concentrations of chemicals known to affect competing plants' and soils' organisms in parts of the plants not previously analyzed.
Technical Abstract: Shrubs have been replacing arid grasslands over large parts of the American southwest for most of the last century. Multiple mechanisms have been proposed to explain this vegetation shift. One hypothesis invokes allelopathy as a mechanism for maintenance of shrub dominance in former arid grasslands. This paper focuses on the presence and distribution of compounds with allelopathic and/or phytotoxic potential found within creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov. Total phenolics, condensed tannins and nordihydroguaiaretic acid (NDGA) were measured in nine categories of tissue within creosotebush. Total phenolic and condensed tannin concentrations were determined using colorimetric methods while NDGA content was determined with high performance liquid chromatography (HPLC). 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 found in all tissues except larger woody stems (5 to 12mm in diameter) with highest concentrations in flowers (1.7 mg/g), seeds (1.1 mg/g), and roots less than 5mm in diameter (1.1 mg/g). Flowers, leaves, green stems and small woody stems (<5mm in diameter) all contained NDGA with highest concentrations in leaves (38.3 mg/g) and green stems (32.5 mg/g). The distribution and nature of secondary compounds are variable among various locations within the plant. Moreover, secondary compounds are present in locations and concentrations that suggest they could have a role in allelopathic and/or phytotoxic interactions with surrounding organisms.