Justicia anselliana(Nees) T. Anders Essential Oils Compounds and Allelopathic Effects on CowpeaVigna unguiculata(L.) Walp Plant

Allelopathic effects of Borreria latifolia on weed germination and identification of allelochemicals

BACKGROUND

Borreria latifolia (Aubl.) K. Schum (Rubiaceae) is an annual weed with a strong allelopathic inhibitory effect on malignant weeds in orchards in southern China. This study was carried out to investigate its allelopathic potential and to identify allelochemicals present in B. latifolia.

RESULTS

Aqueous extracts of B. latifolia inhibited the germination and radicle growth of Eleusine indica and the radicle growth of Bidens alba in a dose-dependent manner. However, only the high-concentration treatment at 50 mg mL-1 delayed the germination of B. alba and Digitaria sanguinalis. Among the root, stem, and leaf aqueous extracts of B. latifolia, the leaf extract had the strongest inhibitory effects on the germination and seedling growth of E. indica, followed by stem extract and then root extract. A total of 47 published allelochemicals, including coumarin, 4-hydroxybenzoate, salicylic acid, 4-hydroxycinnamic acid, and vanillic acid, were identified in the leaf extract. Among the five allelochemicals, coumarin was found to be present in the highest concentration in the leaf extract. Furthermore, coumarin exhibited a significantly greater inhibitory effect on E. indica (EC50 = 36.87 mg L-1) than did the other allelochemicals (EC50 = 100.87-156.30 mg L-1).

CONCLUSION

This study indicates that the leaf extracts of B. latifolia and their allelochemicals have excellent potential as bioherbicides and that coumarin is one of the key allelochemicals in B. latifolia. © 2024 Society of Chemical Industry.

Allelopathic Effects of Amomum villosum Lour. Volatiles from Different Organs on Selected Plant Species and Soil Microbiota

Amomum villosum Lour. is a perennial herb of the Zingiberaceae family, which is widely distributed in Xishuangbanna, Yunnan Province in Southwest China. Large amounts of volatile components contained in this plant enter the surrounding atmosphere and soil through volatilization, foliar leaching, root exudation, and residue decomposition. However, the ecological role of these compounds is currently unclear. The aim of this study was to compare the differences in the composition of volatile oils from stems, leaves, and young fruits of A. villosum, identify chemicals that had allelopathic effects, and explore the effects of the oil on the diversity and composition of soil microbiomes. Volatile oils were obtained by steam distillation and characterized by gas chromatography−mass spectrometry, and then were tested for allelopathic activity using seedlings of Lactuca sativa L. and Lolium perenne L. as test species. The results showed that the oils from stems and leaves were rich in monoterpene hydrocarbons, unlike the oxygenated monoterpenes which dominated oils from young fruits. Leaves > stems > young fruits: this was the order of the allelopathic effects of volatile oils from various A. villosum organs. Among the four main chemical components in the oils, only α-pinene, which is abundant in leaves, had a stronger allelopathic action than the crude oils, implying that it might be a potential allelochemical. Experiments on soil microorganisms indicated that 3.0 mg/mL oil had the greatest effect on the structure of the soil fungal community. It can be concluded that A. villosum is capable of releasing allelochemicals which affect the growth of other plant species and the diversity and community structure of soil microorganisms.

Solanum linnaeanum Leaves: Chemical Profiling of VOCs and Effects on Seed Germination and Early Growth of Monocots and Dicots

Some Solanaceae plants are a rich source of sesquiterpenoid phytoalexins with allelopathic potential. Powder and aqueous extract obtained from the leaves of Solanum linnaeanum Hepper & P.M.L. Jaeger were used to treat the seeds of three target species (Lolium multiflorum Lam., Sinapis alba L. and Trifolium incarnatum L.). Both matrices were evaluated along with untreated controls to determine their toxicity on germination and seedling growth. The results revealed that the pre-emergence treatments were able to be very effective against all three species in the filter paper test by inhibiting the germination up to 100 %. The effectiveness was reduced by the interaction with soil. Despite this, significant data were obtained, albeit different according to the applied matrix. In general, L. multiflorum was the most sensitive to both the action of the leaf powder and aqueous extract while S. alba was found to be the most resistant to powder activity and T. incarnatum had the strongest response to the extract. For the first time, SPME-GC/MS technique was used to characterize the volatile chemical profile of S. linnaeanum leaves. The analyses highlighted the presence of different classes of compounds including terpenoids and sesquiterpenoids potentially useful in the fight against noxious plants both in natural and cultivated ecosystems.

Characteristic aroma-active compounds of floral scent in situ from Barringtonia racemosa and their dynamic emission rates

Barringtonia racemosa is a nocturnal flowering plant. Information on its floral volatiles and the dynamic emission profiles was very limited. In this study, the floral volatiles of B. racemosa were monitored hourly during its florescence via detached and in situ collection for the first time. The dynamic odor activity value (OAV) was calculated to elucidate the active aroma components of floral scent. Results of compositional analyses showed that the predominant floral volatiles were linalool and phenylacetaldehyde. Their emission started around 8:00 p.m., and the peak emissions were 20541 and 18234 ng h(-1) flower(-1), respectively, during 10:00 p.m.-2:00 a.m. Results from dynamic OAV profiling revealed that linalool (409 min(-1)) and phenylacetaldehyde (547 min(-1)) had higher OAVs than other components (<10 min(-1)), indicating that linalool and phenylacetaldehyde contributed mainly to the floral scent with a strong, sweet, and pleasant aroma.

Volatile chemicals from leaf litter are associated with invasiveness of a neotropical weed in Asia

Some invasive plant species appear to strongly suppress neighbors in their nonnative ranges but much less so in their native range. We found that in the field in its native range in Mexico, the presence of Ageratina adenophora, an aggressive Neotropical invader, was correlated with higher plant species richness than found in surrounding plant communities where this species was absent, suggesting facilitation. However, in two nonnative ranges, China and India, A. adenophora canopies were correlated with much lower species richness than the surrounding communities, suggesting inhibition. Volatile organic compound (VOC) signals may contribute to this striking biogeographical difference and the invasive success of A. adenophora. In controlled experiments volatiles from A. adenophora litter caused higher mortality of species native to India and China, but not of species native to Mexico. The effects of A. adenophora VOCs on seedling germination and growth did not differ between species from the native range and species from the nonnative ranges of the invader. Litter from A. adenophora plants from nonnative populations also produced VOCs that differed quantitatively in the concentrations of some chemicals than litter from native populations, but there were no chemicals unique to one region. Biogeographic differences in the concentrations of some volatile compounds between ranges suggest that A. adenophora may be experiencing selection on biochemical composition in its nonnative ranges.