Allelopathic Effect of Serphidium kaschgaricum (Krasch.) Poljak. Volatiles on Selected Species

Abstract

The chemical profile and allelopathic effect of the volatile organic compounds (VOCs) produced by a dominant shrub Serphidium kaschgaricum (Krasch.) Poljak. growing in northwestern China was investigated for the first time. Serphidium kaschgaricu was found to release volatile compounds into the surroundings to affect other plants’ growth, with its VOCs suppressing root elongation of Amaranthus retroflexus L. and Poa annua L. by 65.47% and 60.37% at 10 g/1.5 L treatment, respectively. Meanwhile, volatile oils produced by stems, leaves, flowers and flowering shoots exhibited phytotoxic activity against A. retroflexus and P. annua. At 0.5 mg/mL, stem, leaf and flower oils significantly reduced seedling growth of the receiver plants, and 1.5 mg/mL oils nearly completely prohibited seed germination of both species. GC/MS analysis revealed that among the total 37 identified compounds in the oils, 19 of them were common, with eucalyptol (43.00%, 36.66%, 19.52%, and 38.68% in stem, leaf, flower and flowering shoot oils, respectively) and camphor (21.55%, 24.91%, 21.64%, and 23.35%, respectively) consistently being the dominant constituents in all oils. Eucalyptol, camphor and their mixture exhibited much weaker phytotoxicity compared with the volatile oils, implying that less abundant compounds in the volatile oil might contribute significantly to the oils’ activity. Our results suggested that S. kaschgaricum was capable of synthesizing and releasing allelopathic volatile compounds into the surroundings to affect neighboring plants’ growth, which might improve its competitiveness thus facilitate the establishment of dominance.

Phytotoxic Activity of Alkaloids in the Desert Plant Sophora alopecuroides

“…Two dicot plants, Amaranthus retroflexus and Medicago sativa, as well as two monocot plants, Lolium perenne and Setaria viridis, were selected as receiver species for this study. They were chosen for the following reasons: firstly, they can be found growing in the same habitats as S. alopecuroides; secondly, these four species have previously been used as receiver plants in allelopathic research because of their uniform seedling emergence, high germination rate and their significance in both agricultural and natural fields [3,5,6]. On the other hand, previous work on allelochemical activity in the soil matrix is still insufficient.…”

“…As with many other medicinal plants, S. alopecuroides has been speculated to exhibit allelopathic properties, which presumably facilitates its recent rapid spread in the Yili River Valley of Xinjiang [3,5]. Allelopathy refers to any direct and indirect harmful or beneficial effect by one plant on another through the production of chemical compounds that are released into the nearby environment [6]. It is widely believed that allelopathy may promote the malignant expansion of some invasive plants by releasing allelochemicals such as alkaloids, flavonoids, phenolics, terpenoids, etc., so as to negatively impact neighboring species [7][8][9].…”

Chemical Composition and Phytotoxic Activity of Artemisia selengensis Turcz. Volatiles

“…In fact, the HS-SPME method usually leads to the identification of more compounds from aromatic plants. [40][41][42][43] For instance, 161 peaks and 90 peaks were detected via HS-SPME and HD procedures, respectively, while analyzing the volatiles produced by Echinacea sp., which is consistent with our results. [42] On the other hand, Carvalho et al found that, regardless of the extraction method, the volatiles of Egletes viscosa constituents were largely monoterpenoids and monoterpenes.…”

“…[45] In another study, 50 g of fresh plant material of Thymus proximus in a 1.5 L airtight container completely inhibited the seed germination of A. retroflexus and P. anuua. [40] Zhou et al found that 10 g of fresh Serphidium kaschgaricum in a 1.5 L airtight container markedly suppressed the root elongation of A. retroflexus and P. annua by 65.47 % and 60.37 %, respectively. [20] The inhibitory effect of fresh or living plants on other plants is often due to their rich volatiles, such as eucalyptol, camphene, αthujone, α-terpineol, β-terpineol, p-cymene, and camphor; the inhibitory effect of these volatiles released from various plants on the surrounding plants is conducive to the establishment of their own advantages.…”

“…In conclusion, the phytotoxic activity of the main component, eucalyptol, was significantly lower than that of the A. selengensis EO; however, it was difficult to confirm the existence of synergistic effects because some of the other abundant constituents were not commercially available thus their activity was not measured. Eucalyptol, also known as 1,8-cineole, is a major component of many plant volatiles, such as Serphidium kaschgaricum (38.68 %), Elsholtzia fruticosa (40.10 %), and Eucalyptus saligna (29.01-32.51 %); [40,49,50] it is also a major constituent of many Artemisia plants, such as A. verlotiorum (21.00 %), A. argyi (22.03 %), and A. austriaca (10.75 %). [17,51,52] Eucalyptol (1,8-cineole) is one of the most effective monoterpenes in plant EOs.…”