Abstract
Haloxylon persicum is a well-known plant of sandy deserts, but yet, its allelopathic and phytochemical potential has not been explored. In the present study, we evaluated the effects of different concentrations (1, 2, 4, and 8%) of the aqueous extract of H. persicum shoots on seed germination and seedling growth of wheat crop and black mustard weed. The effects of the same extract on the biochemical parameters (chlorophyll a, chlorophyll b, carbohydrates content, and proline content) of wheat seedlings were also investigated. Low and moderate concentrations (1, 2, and 4%) of H. persicum aqueous extract nonsignificantly affected seed germination, shoot length, root length, fresh weight, and dry weight of wheat seedlings, whereas these parameters were negatively affected by the application of the highest extract concentration (8%). The results revealed a significant increase in proline content in wheat seedlings under all the applied concentrations of H. persicum extract. Low and moderate concentrations (1–4%) of H. persicum extract significantly enhanced chlorophyll a, chlorophyll b, and total chlorophyll content in wheat seedlings, whereas these parameters were significantly reduced when the highest extract concentration (8%) was applied. Only the lowest concentration (1%) of H. persicum extract reduced the carbohydrates content of wheat seedlings, while other concentrations showed nonsignificant effects. Concentrations of 4 and 8% of H. persicum extract reduced the seed germination percentage of black mustard. The root length, shoot length, and fresh weight of black mustard seedlings were significantly decreased by the application of 1 and 2% extract concentrations and completely inhibited in response to treatment with 4 and 8% concentrations. The dry weight of black mustard seedlings was not affected by 1 and 2% extract concentrations but completely inhibited at 4 and 8% concentrations. The methanol extract of H. persicum contains high contents of bioactive secondary metabolites, such as phenolics, flavonoids, flavonols, anthocyanins, tannins, saponins, as well as proved to has a very strong antioxidant activity of the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH). Based on our results, we recommend the potential application of the aqueous extracts of H. persicum to control black mustard weed in wheat crops. Furthermore, H. persicum revealed an interesting phytochemical pattern with sound antioxidant activity that assigns this plant as a promising candidate to explore its detailed metabolomics profile along with potential bioactivities.
Highlights
One of the major challenges to wheat growth and yield is its interspecific competition with weeds, such as black mustard (Brassica nigra (L.) Koch), for environmental resources [1,2,3,4]
The present study aimed to evaluate the allelopathic effects of the aqueous extract of H. persicum on wheat crops and black mustard weed
The concentrations of 2–8% of the aqueous extract of H. persicum significantly reduced the germination rate in black mustard, whereas the germination rate of wheat was only significantly reduced due to treatment with the highest concentration of H. persicum extract (8%) (Figure 1A,B).On the last day of the experiment, 4–8% extract concentrations signifiAgronomy 2021, 11, x FOR PEER REVIEcaWntly reduced the germination percentage in black mustard seeds (p < 0.05), where7asofth1i9s trend was observed in wheat only under the highest concentration (8%) (Figure 2)
Summary
One of the major challenges to wheat growth and yield is its interspecific competition with weeds, such as black mustard (Brassica nigra (L.) Koch), for environmental resources [1,2,3,4]. Plants represent a rich source of biologically active molecules with species-specific allelopathic potential by supporting the growth of some species and retarding the growth of others at the same time [10,11,12] These phytochemicals belong to diverse groups, including phenols, alkaloids and terpenes [13], saponins [14,15], glucosinolates and their enzymatic degradation products (isothiocyanates) [16], with varying concentrations in different plant species [17]. These metabolites affect some plant species by altering the plant’s biological fluxes, affecting photosynthetic pigments [18,19], which leads to the inhibition of seed germination, and root and shoot growth [14]. Most of these allelochemicals are soluble in water and are found in all plant parts, such as root, stem, rhizome, leaves, flowers, fruits, and seeds [13,14,15,16], and so can be used in foliar as well as soil applications for their desired positive or negative effects on seeds, seedlings, or adult plants [20,21]
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