Analysis of phenolic compounds and allelopathic effects of Eucalyptus on Prosopis cineraria

Abstract

The Eucalyptus has been extensivley planted in Pakistan in native forests because of its fast-growing and adaptability to different habitats. Allelopathic and ecological effects are receiving severe concern with the growth of more plantations of Eucalyptus. Since the Eucalyptus has allelopathic effects on neighboring plants. The effect of the exotic Eucalyptus leaf litter and ash on Prosopis cineraria germination and growth was observed. The three concentrations of leaf litter and ash 10, 20 and 30% were applied, as were the controls (without leaf litter and ash). The germination and growth parameters of Prosopis cineraria were analyzed. The phenolic acids were identified and quantified through HPLC from laboratory experiments soil. The laboratory experiments soil was analyzed for soil properties such as; EC, pH, OM, N, P, K, and Na. The germination was observed to be reduced in leaf litter and ash applied treatments.  After germination, mortality of seedlings at the early stage was recorded in leaf litter ash applied treatments. Leaf number, shoot elongation ratio, length of shoot, root length, relative biomass ratio, amount of chlorophyll, fresh and dry weight of seedlings were found to have decreased. In soil mixed with leaf litter, nine phenolics; hypogallic acid, gallic acid, 2, 4, 6-trihydroxybenzoic acid, protocatechuic acid, pyrogallolaldehyde, caffeic acid, m-coumaric, o-coumaric and p-coumaric acid were analyzed through the HPLC. 2, 4, 6-trihydroxybenzoic acid was predominant with concentration of 34.51 mg/100g. In soil mixed with ash, gallic acid, protocatechuic acid and pyrogallolaldehyde were analyzed. Gallic acid was predominant in leaf litter ash 30% with concentration of 11.44 mg/100g. The pH of the soil decreased in leaf litter. OM, EC, K, N, P and Na have increased in treatments. Higher EC and Na were noted in the ash. A negative correlation was seen between concentration and the plant parameters studied. Eucalyptus has deleterious effects on the native species, Prosopis cineraria. Therefore, Eucalyptus should not be planted along with native trees or in native forests in Pakistan. Thus, it is also recommended that Eucalyptus trees be replaced with native species.