Allelopathic potential of the phenolics from the roots of Pluchea lanceolata

Aqueous leachates of roots of the perennial weed Pluchea lanceolata (DC.) C. B. Clarke, its root‐incorporated soil and rhizosphere soil, interfered with the seedling growth of certain plant species. The soils from the rhizosphere zone of this plant had significantly higher total phenolics and HPLC analysis revealed that phenolic fractions represented by retention times of 1.6, 1.9, 2.5 (simple phenol, chlorogenic acid and phloroglucinol respectively), 3.7 and 4.3 min were contributed by roots of the weed to the soil. The phenolic fraction represented by the retention time 3.3 (formononetin 7‐O‐glucoside) was detected in the weed's rhizosphere soils and not in the rootincorporated soils. UV spectral studies established the presence of phloroglucinol, simple phenol, chlorogenic acid, formononetin 7‐O‐glucoside, and methylated coumarins in the root leachate, which affect the seedling growth of mustard (Brassica juncea). Present research established the allelopathic potential of P. lanceolata roots, and the possible involvement of allelopathy in its interference success.