Allelopathic effects of phenolics and terpenoids extracted from Gmelina arborea on germination of Black gram (Vigna mungo) and Green gram (Vigna radiata)

The allelopathic influence of Gmelina arborea was determined on the seed germination and seedling growth of green gram and black gram. Their dried leaves were collected and the active principles were extracted. A Thin Layer Chromatography was performed which indicated the presence of polyphenols and terpenoids. The extract was subjected to FTIR analysis and GC-MS. FTIR spectrum showed a –OH stretch at 3416 cm⁻¹ C-O stretch and C-H stretch at 1127 cm⁻¹ & 2924 cm⁻¹ respectively. Indication of the presence of phenolic and terpenoid based compounds which was confirmed by MS. GC-Mass Spectrometric analysis showed characteristic peaks corresponding to terpenoids like Shiromodiol diacetate, 2 Butyl methacyclate, Brusatol and Menthofuran and phenolic compounds like Coumaric acid, Gallic acid, Syringic acid and Vanillic acid. In laboratory bioassay, the effects of extracts were determined on the seed germination and seedling growth of test crops. The G. arborea extracts inhibited the germination, seedling growth and the total protein content of both test crops. The PASS (Prediction of Activity Spectra for Substances) prediction showed that the compounds present in G. arborea extracts inhibited the proteolytic enzymes [Phosphatase and Propyl aminopeptidase (Pa>70%)], important for seed germination. Thus allelochemicals inhibited the activity of these enzymes and thereby either retarded the seed germination. Hence some preventive measures may be taken to minimize the water drainage from these tree orchards grown for wood, pulp and fuel wood.