Allelopathic interference of Hovenia dulcis extracts on the germination and development of Parapiptadenia rigida

This paper reports the influence of ethanolic extracts of fresh and dried leaves, pseudofruits, seeds, bark and roots of the invasive plant Hovenia dulcis Thunb. on seed germination and seedling development of the native tree Parapiptadenia rigida (Benth.) Brenan. Fresh adult and young organs of H. dulcis were extracted by maceration, while the extracts of the corresponding dried and pulverized plant material were obtained by percolation using soxhlet. The parameters germination, emergence velocity index (EVI), length and dry weight of radicles and hypocotyls of P. rigida were evaluated under influence of H. dulcis extracts in concentrations of 0, 25, 50, 75 and 100 mg mL-1. Extracts of fresh plant materials provided yields varying between 5.7 and 9.7%, while extracts of dried organs showed values ranging from 14.0 to 35.5%. The allelopathic activity of extracts on P. rigida differed according to the plant organ of the donor species and showed to be concentration dependent, in addition to being influenced by the state of the extracted plant material. The allelopathic effects of H. dulcis extracts on P. rigida affected different stages of its development and were caused by allelochemicals present in distinct plant organs.