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As a native of the Chihuahuan desert, guayule (Partheniumargentatum Gray) has a history of dealing with low water availability. Agronomic studies have shown that increasing irrigation increases overall rubber yields, but decreases rubber concentration per plant. As water availability is an important factor in agricultural production, this study was conducted to examine how drought affects plant growth and secondary compound distribution throughout the plant. One-year-old guayule plants were subjected to water stress from June through August, in 2003 and 2004. The well-watered treatment was irrigated daily, and the drought-stressed plants were irrigated when the soil water potential reached 6 (0.6) or 3 (0.3) bars (megapascals) in 2003 and 2004, respectively. Plant growth was monitored by measuring height, width, and stem diameter. Fresh weight of shoots and roots was recorded at harvest, and a subset of plants were defoliated and used to determine leaf weight and area. Resin and rubber were extracted from dried and ground plant samples. Growth, leaf weight, and leaf to stem ratio were decreased in the drought-stressed plants compared to the well-watered plants. Rubber concentration, but not resin concentration, was higher in the drought-stressed plants. There were no significant differences in resin and rubber concentration in the leaves and roots of the different treatments; however, they were both higher in the stems of the drought-stressed plants. In guayule, rubber is deposited mainly in the bark parenchyma of the stems. The drought-stressed plants had a greater contribution of stem biomass to overall biomass and a reduced stem diameter with higher bark to wood ratio, which could account for the higher rubber concentration in the drought-stressed plants.

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In addition to the primary metabolism (growth) present in all living beings, plants have a secondary metabolism (protection) that allows production and accumulation of compounds of a diverse chemical nature called SMs, which are distributed

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). Nutrient-deficient plants often have lower growth rates and higher concentrations of carbon-based (nonnitrogen-containing) secondary compounds (CBSCs) than do plants with access to ample nutrients ( Bryant et al., 1983 ; Coley et al., 1985 ). This negative

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Plants are sessile organisms that use numerous mechanisms to respond to dynamic environmental factors. One such factor is light, which is a powerful elicitor of primary and secondary metabolism that ultimately affects the chemical and sensory

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. prostrata was first recorded by Holm et al. (1979) and described by Ho (2000) in Vietnam. Some previous studies have confirmed that E. prostrata contains different natural compounds such as flavonoids, alkaloids, triterpenoids, saponins, phenolics

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and flavonoid compounds ( Maudu et al., 2010 ). These secondary metabolites are compounds synthesized from primary metabolites as the plant interacts with its environment for adaptation or defense ( Ramakrishna and Ravishankar, 2011 ). The compounds

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; Ślesak et al., 2008 ; Vogt et al., 1999 ). In addition, this plant possesses the ability to rapidly accumulate phytochemicals and secondary metabolites, such as beta-carotene, pinitol, betacyanin, phenolic compounds, and flavonol conjugates, in a cell

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( PPF ) of 650 μmol·m −2. s −1 . Carvone analysis. Levels of the secondary compound (−)-carvone, the dominant component of spearmint oil, were analyzed in treated spearmint plants. (−)-Carvone concentrations have been previously shown to be

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ingredients is shown in Fig. 2 . Table 1. Delustering voltages, collision voltages, and collision chamber emission voltages of the medicinal compounds. Fig. 2. Secondary mass spectrum of six active pharmaceutical ingredients. ( 1 ) Eleutheroside B, ( 2

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Glucosinolates and carotenoids are two classes of secondary metabolites in the Brassicaceae that are important in plant metabolism and for the dietary health benefits that they convey. Glucosinolates are sulfur-containing compounds present in a

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