Allelopathic potential of Eucalyptus urograndis on lettuce and Brazilian native forest species of Cedrela fissilis Vell.

The Eucalyptus urograndis is widely used in Brazil, including in agroforestry systems. Cedrela fissilis is a potential plant species to be used in agroforestry systems or intercropped with E. urograndis. Therefore, it is necessary to investigate the allelopathic potential of the hybrid on this species. This work aimed to investigate the allelopathic potential of E. urograndis leaves and litter on the germination and growth of Lactuca sativa and Cedrela fissilis species. Leaves and litter were collected and extracted with ethanol to obtain crude extracts (CEE), which were then fractionated to obtain hexane (FHex), dichloromethane (FDCM), ethyl acetate (FAcOH), butanol (FBuOH) and aqueous (FAq) fractions. For the allelopathic potential assay, the samples were tested for percentage of germination (%G), germination speed index (GSI), shoot and root length and dry mass of seedlings using a triple-factorial design (2 x 6 x 5). Sample concentrations were of 1.25; 2.5; 5.0 and 10.0 mg/L using L. sativa and C. fissilis seeds with 5 replicates of 20 seeds for each. Gas chromatography (GC/MS) was used to analyse the most active samples. The CEE, FHex and FDCM samples of leaves and litter had a negative effect on the variables analyzed for L. sativa and C. fissilis. The FAcOH, FBuOH and FAq fractions influenced the initial growth of the plant’s seeds. FDCM was more active in the reduction of germination and inhibition of initial growth of both species. Lactuca sativa and Cedrela fissilis were negatively affected by the leaves and litter of Eucalyptus urograndis.