Effect of decomposition of leaves of Azadirachta indica A. Juss. on germination and growth of Myracrodruon urundeuva Allemão

Abstract

Azadirachta indica have allelopathic potential, attributed to the presence of allelochemicals capable of altering plant diversity in surrounding areas. This work aimed to evaluate if the decomposed leaves of A. indica can affect the germination and growth of Myracrodruon urundeuva. A. indica leaves were collected at the end of senescence and mixed with soil in different concentrations and decomposed for 90 and 180 days. Through phytochemical analysis, it was found the presence of diterpenes and triterpenes, such as margocinolide, epoxyazadiradione and salimuzzalin. Leaf decomposition negatively affected germinability, emergence speed and the germination synchrony index of M. urundeuva, especially during the first decomposition period. The residues of the leaves of A. indica also negatively affected the length of the young plants of M. urundeuva, since the lengths of the stem and root were reduced, and the treatment of lower concentration a reduction in root length was observed only in the first decomposition period (T1). Leaf residues in the first decomposition time also negatively influenced the total biomass of M. urundeuva, in all treatments evaluated. The decomposition were also able to change the amount of photosynthetic pigments in the first decomposition period, since the total chlorophyll content had a reduction from the average value of 3.23 to 2.40 g/kg, corresponding to a 25.71 inhibition. The observed results suggest that the compounds present in the litter of A. indica have an allelopathic action, being necessary to limit the use of the former in areas that need ecological restoration and in preserved natural environments.