Abstract
Exploration of allelochemicals with phytotoxic effects is intended to minimize a current dependency on synthetic herbicides in weed management. Several allelochemicals from the tropical tree <em>Cerbera manghas</em> (sea mango) have been reported as termiticides and bactericides. The present study investigated possible phytotoxic effects of <em>C. manghas</em> leaf extracts under laboratory conditions. Four monocots: barnyard grass (<em>Echinochloa crus-galli</em>), foxtail fescue (<em>Vulpia myuros</em>), Italian ryegrass (<em>Lolium multiflorum</em>), and timothy (<em>Phleum pratense</em>) and four dicots: alfalfa (<em>Medicago sativa</em>), garden cress (<em>Lepidium sativum</em>), lettuce (<em>Lactuca sativa</em>), and rapeseed (<em>Brassica napus</em>) were used as test species. Elongation of both shoots and roots of seedlings was measured to assess any phytotoxic effects. The results showed that the sensitivities of shoots and roots were different between the test species, and the inhibition of seedling elongation significantly increased with increasing concentration of leaf extracts of <em>C. manghas</em> for all the test species. The IC<sub>50</sub> (50% inhibitory concentration) values showed that 8.50–32.30 and 4.26–34.67 mg dry weight equivalent extract mL<sup>−1</sup> of <em>C. manghas</em> inhibited seedling elongation by 50%, for shoots and roots respectively. Isolation and identification of the phytotoxic substances from <em>C. manghas</em> are suggested for future investigation.
Highlights
Weed control by applying synthetic herbicides has long been an established agricultural practice [1]
The bioassays indicated that leaf extracts of C. manghas significantly inhibited seedling elongation for all the test species at certain concentrations of the extract
Inhibition increased with increasing extract concentrations and the sensitivity of shoots and roots was different for the test species (Fig. 1)
Summary
Weed control by applying synthetic herbicides has long been an established agricultural practice [1]. The excessive use of synthetic herbicides in weed control has led to many environmental problems including toxicity to non-target species, weed resistance, water and soil pollution, and human health issues [2]. Many researchers are paying more attention to sustainable and friendly environmental control methods for minimizing the dependency on synthetic herbicides. One way is to utilize an allelopathic utility as an alternative strategy for weed control, as well as providing environmental safety [3]. The exploitation of allelopathic responses provides a safe method for controlling weeds [3,4]. It has been reported that many plants are important as a source of allelochemicals which show phytotoxic activity [5]. Allelochemicals are available and these are released from
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