Phytotoxic effects of Morus nigra aqueous extract on germination and seedling growth of Lactuca sativa

Abstract

Some exotic species threat the integrity of natural environments due to their invasive potential. They can affect other species by releasing secondary compounds in the soil. Morus nigra (Moraceae) is an invasive species of riparian forests in southern Brazil. The objective of this study was to verify if the aqueous extracts of fruit, fresh and dry leaves of M. nigra show phytotoxic effects on germination, seedling growth and membrane integrity of seedlings of Lactuca sativa. Extract concentrations of 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5 and 10% were tested. Germination rate and speed of germination were determined. Effects on initial growth were evaluated by measuring seedling root and shoot length, and membrane integrity was assessed by conductivity tests. Results showed the phytotoxicity of M. nigra aqueous extracts, causing significant inhibition on germination and seedling growth. The fruit extract was generally less phytotoxic than extracts from fresh and dry leaves. Moreover, the extracts induced changes in membrane integrity and caused morphological deformities in seedlings, such as necrotic roots and chlorotic plants. The high phytotoxicity of fruit, dry and fresh leaf extracts of M. nigra was evidenced, indicating the allelopathic potential of the species.

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“…MDA is an indicator metabolite of lipid peroxidation reactions (peroxidation of unsaturated fatty acids in membranes). The lipid peroxidation products are potential biomarkers for oxidative stress status (Vieira et al 2018). Hence, changes in membrane integrity, permeability, and fluidity could be caused by ROS production and accumulation.…”

“…Hence, changes in membrane integrity, permeability, and fluidity could be caused by ROS production and accumulation. These ROS can affect membranes, and result in DNA and protein damages, leading to cell death (Vieira et al 2018). As a result, the increase of the antioxidant status responses, either in leaves or in roots, could be an alleviation of allelopathicinduced oxidative stress.…”

Assessment of Phytotoxins Using Different Technologies

“…To date, a number of the antifungal, antimicrobial, and antibacterial effects of these compounds have been reported by various researchers [9][10][11][12][13]. Phytotoxins include various secondary metabolites and biochemical constituents produced by different plant parts such as leaves, stems, roots, flowers, seeds, fruits, and so on [14][15][16][17]. The most essential phytotoxins identified are phenolic compounds [18,19], quinones [20], terpenoids [21], alkaloids [22], glycosides [23], and flavonoids [24], The disruption of photosystems I and II, and the inhibition of chlorophyll synthesis, mitosis, and amino acid synthesis are the main modes of action associated with phytotoxins [25].…”