Alelopatia de extratos vegetais sobre Eragrostis plana Ness e hidrólise da sua biomassa para prospecção de compostos químicos

Abstract

The Eragrostis plana Ness (annoni grass) is known as an invasive plant of difficult controlling due to its characteristics as rapid spread of its seeds, drought, and allelopathic potential detrimental to the development of many native plant species. The main form of control of this species is through the use of herbicides. However, the use of herbicides causes several environmental problems. Therefore, this study aims to evaluate the efficiency of plant extracts in the control of annoni grass, in addition to performing subcritical water hydrolysis to obtain sugars and other organic compounds contained in the biomass. Leaf extracts were obtained from faux-billet (Coleus barbatus), leucaena (Leucaena leucocephala), and eucalyptus (Eucaliptus camaldulensis) by three extraction methods: infusion, extraction with pressurized liquid, and ultrasound-assisted extraction. The extracts were applied in the pre-and postemergence of the species in experiments carried out using the germination method in roll and using a substrate. For the hydrolysis of annoni grass biomass, temperatures of 180 and 220ºC and solvent to solids mass ratio of 5 and 10 g/g were evaluated for collection times of 1, 2, 3, 4, 5, 8, and 10 minutes. The sugars and other organic compounds contained in the hydrolysates were quantified by liquid chromatography. The extracts from faux-billet and eucalyptus reduced the germination and growth of annoni grass, and the extracts with eucalyptus leaves were the most efficient in the control of this grass, reducing the germination by 63.33%, shoot length by 52.23%, and root length by 45.55% when compared to the control. The extracts obtained from leucaena leaves, depending on the method used, did not present significant effect on germination, while the germination speed index increased in 38.53% when using extract obtained by pressurized liquid. Sugars such as glucose, xylose, arabinose, and cellobiose, acids such as acetic, formic, and levulinic, and inhibitors such as 5-hydroxymethylfurfural and furfural were quantified in the hydrolysates. Glucose and xylose and formic and acetic acids were found in higher amounts in the hydrolysates.