Guaianolide Derivatives from the Invasive Xanthium spinosum L.: Evaluation of Their Allelopathic Potential

New Findings from the Volatiles of the Corsican Liverwort Porella arboris-vitae: An Evaluation of Their Allelopathic Effect

The volatile metabolites of the Corsican liverwort Porella arboris-vitae and their allelopathic implication were studied for the first time. Volatile compounds of the essential oil, hydrosol, and ether extract were investigated using gas chromatography (GC), GC-mass spectrometry, and nuclear magnetic resonance. Drimane and pinguisane derivatives were dominant in the plant. The study highlights an analytical strategy involving metabolite enrichment by column chromatography and comprehensive analytical experiments to identify compounds with incomplete spectral data from the literature. Among them, the drime-7-en-11-acid methyl ester hitherto described as a synthetic intermediate was described here for the first time in its natural state and a sesquiterpene alcohol was newly discovered. The allelopathic effect of P. arboris-vitae volatile metabolites was evaluated on two monocotyledonous species, rice and leek, and two dicotyledonous species, radish and watercress. Essential oils, hydrosols, and ether extracts inhibited the germination and seedling growth, highlighting the potential of bryophyte for developing novel herbicides.

Effects of Different Degrees of Xanthium spinosum Invasion on the Invasibility of Plant Communities in the Yili Grassland of Northwest China

Studying the effects of different degrees of exotic plant invasion on native plants' community structure and plant diversity is essential for evaluating the harm caused to ecosystems by plant invasion. In this study, we investigated the effects of Xanthium spinosum, a widespread invasive species, on plant community species diversity and community stability in the Ili River Valley area of Xinjiang, China, under three invasion levels (no invasion and low, moderate, and heavy invasion), and the competitive advantage index, invasion intensity, and contribution of plant community species diversity to community stability and invasibility were determined for the prickly fungus under different degrees of invasion. The results show that there were significant differences (p < 0.05) in the species diversity and community stability of plant communities caused by different degrees of invasion of X. spinosum. The species diversity and stability of plant communities were negatively correlated with the community invasibility, competitive advantage, and invasion intensity of X. spinosum (p < 0.05); therefore, the competitive advantage and invasion intensity of X. spinosum increase with the increase of its invasion degree. On the contrary, community species diversity and stability decreased with the increase of its invasion degree, ultimately leading to differences in community invasibility under different invasion degrees. The Shannon-Wiener and Simpson's indices were the greatest contributors to community stability and invasibility, respectively. Moderate and heavy levels of invasion by X. spinosum reduced the diversity and stability of local plant communities, increased the invasibility of communities, and substantially affected the structures of plant communities. Therefore, the continued invasion by X. spinosum will have an immeasurable impact on the fragile ecosystems and diversity of indigenous species in Xinjiang. We recommend that this invasive species be controlled and eradicated at the early stages of invasion to prevent further harm.