Identification and Quantitation of Compounds in a Series of Allelopathic and Non-Allelopathic Rice Root Exudates

Abstract

An investigation of the chemical basis for rice allelopathy to the rice weed arrowhead (Sagittaria montevidensis) was undertaken using GC/MS and GC/MS/MS techniques. Twenty-five compounds were isolated and identified from the root exudates of both allelopathic and non-allelopathic rice varieties. Phenolics, phenylalkanoic acids, and indoles were among the chemical classes identified. Two indoles previously unreported in rice were detected in the exudates, 5-hydroxy-2-indolecarboxylic acid and 5-hydroxyindole-3-acetic acid. Several other compounds identified in this study have not previously been reported in rice root exudates, namely mercaptoacetic acid, 4-hydroxyphenylacetic acid, and 4-vinylphenol. The levels of 15 compounds present in the exudates were quantified using GC/MS/MS. Six of the seven most abundant compounds were phenolic acids. Significant differences exist between the allelopathic and non-allelopathic cultivars in their production of three of these six compounds. Greater amounts of trans-ferulic acid, p-hydroxybenzoic acid, and caffeic acid were detected in the exudates of allelopathic cultivars. The seventh compound, abietic acid, was significantly higher in the non-allelopathic cultivars.

Allelopathic Activity of Dehulled Rice and its Allelochemicals on Weed Germination

“…Furthermore, dehulled rice released more gallic and cinnamic acid than rice (P<0.05). Seal et al [32] isolated and identified 25 compounds from the root exudates of both allelopathic and non-allelopathic rice varieties. Among the identified compounds, there were ten phenolic acids including salicylic, t-cinnamic, 2-hydroxyphenylacetic, p-hydroxybenzoic, 4-hydroxyphenylacetic, vanillic, syringic, p-coumaric, t-ferulic and caffeic acids.…”

Intercropping of field crops in cotton for the management of purple nutsedge (Cyperus rotundus L.)

“…These include sorghum , rice (Seal et al 2004), and wheat (Huang et al 2003). Recently Iqbal and Cheema (2007) reported effective control of purple nutsedge through the utilization of natural plant extracts from various allelopathic crops (sorghum, sunflower and brassica) in the field.…”

Exudados de la raiz y su relevancia actual en las interacciones alelopaticas

“…Ecológicamente, se han propuestos cuatro mecanismos para la excreción de los aleloquímicos al ambiente, donde cada uno de ellos han demostrado la eficacia de tal mecanismo, involucrando fenómenos de volatilización, [101][102][103][104][105][106][107] lixiviado, 108-113 descomposición de partes de la planta en el suelo [114][115][116][117][118] y exudados por raíz. [119][120][121][122][123][124][125][126][127] Estos mecanismos implican que los aleloquímicos pueden encontrase en cualquier parte de la planta, y que la dinámica de su actividad es una función del mecanismo en que este pueda ser liberado. Por ejemplo, la descomposición de residuos vegetal implica material senescente, que no implica una función activa de la planta, mientras que volatilización y exudados de raíz, son procesos extremadamente activos donde está involucrado el tejido vivo de la planta.…”

“…Aleloquímicos como ácidos hidroxámicos y momilactona también han sido observados a variar con la especie. 48,195,196,197 Fenología Altos niveles de concentración en estados tempranos de desarrollo (germinación y plántulas). Rasgo característico en plantas exudando ácidos fenólicos y hidroxámicos.…”