Antigerminative comparison between naturally occurring naphthoquinones and commercial pesticides. Soil dehydrogenase activity used as bioindicator to test soil toxicity.

As important secondary plant metabolites, naphthoquinones exhibit a wide range of biological activities, and one of their roles in the competition among plants is a well-known process called allelopathy. Their potential as a sustainable alternatives to herbicides has been investigated. In this study, we aim to take advantage of these naturally occurring substances to control the germination of spontaneous flora. In this work, the sensitivity of the germination of different plant species (horticultural, grasses and spontaneous flora) was tested. The results indicate that most of the plants are sensitive to juglone. The comparison between naphthoquinones and commercial pesticides did not provide enough evidence to use naphthoquinones to control spontaneous flora. Assessing the toxicity of pesticides is crucial because the sustainability of the ecosystem could be endangered by their use. In this study, the toxicity of certain pesticides (metam Na, oxyfluorfen, glyphosate, metribuzin and diuron) was evaluated based on dehydrogenase activity (DHA). DHA has become a good bioindicator for assessing the toxicity of xenobiotics. A toxicity index was proposed to compare the different degrees of toxicity among the tested substances. Finally, a toxicity threshold was constructed using the slopes of the fitted lines of the data, assuming that the maximum toxicity (10) represented the slope of the biocide HgCl2 and that the minimum toxicity (1) was attributed to the DHA obtained from soil without pesticides.