Abstract
The depsides atranorin (7) and diffractaic acid (1), the depsidones hypostictic (2) protocetraric (3), salazinic (4) acids, the xanthone secalonic acid (5), and usnic acid (6) were evaluated for their phytotoxic potentials against the target species Allium cepa cv. Baia periforme (onion, Monocotyledoneae). The bioassays, carried out under laboratory conditions, revealed that diffractaic (1) and hypostictic (2) acids stimulated plant growth; secalonic acid (5) stimulated seed germination and radicle growth, while reducing coleoptile length. Usnic acid (6) promoted seed germination and stronger inhibition of radicle and coleoptile growth. Protocetraric (3) and salazinic (4) acids and atranorin (7) exhibited a herbicidal effect, inhibiting seed germination and reducing radicle and coleoptile growth—features that suggest their utility as natural herbicides. These results invite further investigation to elucidate the mode of action of these compounds and to synthesize them for field experiments. DOI: http://dx.doi.org/10.17807/orbital.v7i3.756
Highlights
The current demand for large-scale food production has greatly increased the agricultural use of synthetic pesticides, but considerable efforts have been made to reduce their use, both to diminish their levels in foods and to decrease the environmental impact of agriculture [1]
The search for natural pesticides has gained impetus following the observation of undesirable effects of synthetic herbicides on ecosystems
Nuclear magnetic resonance (NMR) spectroscopy was performed on a Bruker DPX-300 spectrometer using the solvent as an internal reference
Summary
The current demand for large-scale food production has greatly increased the agricultural use of synthetic pesticides, but considerable efforts have been made to reduce their use, both to diminish their levels in foods and to decrease the environmental impact of agriculture [1]. The search for natural pesticides has gained impetus following the observation of undesirable effects of synthetic herbicides on ecosystems. Plants have chemical defense mechanisms that involve phytotoxins, or allelochemicals—secondarymetabolism compounds that provide protection against other plants, phytophagous insects, and herbivorous predators. This phenomenon is known as allelopathy [2]. Many secondary compounds from plants, microorganisms, and lichens are toxic to insects, microbes, and other organisms. Secondary metabolites of lichens are most likely involved in defense mechanisms against insects and herbivores, parasitism by other fungi, and competition from bryophytes, vascular seedlings, and other lichens [5]
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