Invasive alien species are becoming more and more prevalent worldwide,Erigeron bonariensisandBidens pilosaare two invasive species of Asteraceae in Egypt. To mitigate their detrimental effects and understand their differences in invasiveness, we compared the allelopathic potentials ofE. bonariensisandB. pilosausing leachates, decaying residues, and volatilization processes. Notably, the allelopathic variances in leachates were significant, influenced by plant types, concentrations, and response patterns of target plant traits, as indicated by EC₅₀. The relative phytotoxicity of the invasive species decayed residues peaked between 20 and 25 days in the soil, with a positive correlation with concentrations and soil properties. The highest quantities of phenolic acids were chlorogenic acid and caffeic acid reaching (5.41 and 4.39 µg g⁻¹)E. bonariensisand (4.53 and 4.46 µg g⁻¹)B. pilosa, in leachates extracts respectively, while in the soil extract of decayed residues were coumaric acid and ferulic acid measuring (1.66 and 1.67 µg g⁻¹)E. bonariensisand (1.47 and 1.57 µg g⁻¹)B. pilosa, respectively. Using GC/MS analysis, the main volatile components inE. bonariensiswere 1, 8 cineole (5.62%), and α-terpinene (5.43%) and iso-Caryophyllene (5.2%) which showed the greatest inhibitory effects. While B. pilosamain constituents were trans-sabinene (5.39%) and Camphene (5.11%), respectively. Finally, the high invasion level displayed fromE. bonariensis(0.221) compared withB. pilosa(0.094) which correlated with the stronger allelopathic activities against plant species, and soil properties. Therefore, the allelopathic potentialities of these species are critically relevant to their invasion success.

Fucoidan is one of the main polysaccharides of brown algae and echinoderm, which has nutritional and pharmacological functions. Due to the low molecular weight and exposure of more sulfate groups, oligo-fucoidan or fucoidan oligosaccharides have potential for broader applications. In this research, a novel endo-α-1,4-L-fucoidanase OUC-FaFcn1 which can degrade fucoidan into oligo-fucoidan was discovered from the fucoidan-digesting strain Flavobacterium algicola 12,076. OUC-FaFcn1 belongs to glycoside hydrolases (GH) family 107 and shows highest activity at 40 °C and pH 9.0. It can degrade the α-1,4 glycosidic bond, instead of α-1,3 glycosidic bond, of the fucoidan with a random tangent way to generate the principal product of disaccharide, which accounts for 49.4% of the total products. Therefore, OUC-FaFcn1 is a promising bio-catalyst for the preparation of fucoidan-derived disaccharide. These results further enrich the resource library of fucoidanase and provide the basis for the directional preparation of fucoidan-derived oligosaccharide with specific polymerization.

Citrullus lanatus var. Colocynthoide “Gurum” is an unconventional crop that can be utilized as a new source of edible oil and has the ability to grow in a variety of harsh conditions. To mitigate the adverse effects of salinity on seed germination and plant performance of C. lanatus, seeds were primed in the aqueous extracts of the seaweed Ulva lactuca before planting under greenhouse conditions. The aqueous extract of U. lactuca at 8% w/v led to maximal seed germination percentage and seedling growth of C. lanatus. Moreover, U. lactuca extract counteracted the negative effects of salt stress on the plant by significantly increasing the activity of SOD, CAT, and POD. The bioactive components of U. lactuca, e.g. glycine betaine and phenolic compounds can account for such beneficial role of algal extract on C. lanatus. Thus, priming of C. lanatus seeds in U. lactuca extract with various concentrations of U. lactuca extract can be employed as an effective practice for successful seed germination, improved plant growth and enhanced salt resistance, probably as a result of increased antioxidant enzymes activity and photosynthetic pigments.

The potentials of Chenopodium species are important for both the environment and agricultural production. To comprehend their effects, their allelopathic pathways were investigated. The impacts of C. album, C. murale, and C. ambrosioides weeds were compared via leachates of water extracts, decaying residues, and volatilization and measured biologically and chemically on plant traits and soil characteristics. The allelopathic effect of water extracts from the aboveground parts was more potent than that from the subterranean parts, significantly influenced by the plant parts and concentrations. The allelochemicals determined by LC-ESI-MS were coumaric and ferulic acid, with concentrations of 4.74 and 5.72 μg ml^-1 for C. album, 7.07 and 5.71 μg ml^-1 for C. murale, and 8.88 and 4.82 μg ml^-1 for C. ambrosioides, respectively. The allelopathic effect of incorporated residues into soil was affected significantly by plant types, concentration, and their interactions. The essential oils of shoot parts showed the strongest suppression in B. rigidus and C. arvensis germination and growth. The principal components of essential oils determined by GC-MS were ascaridole (C. ambrosioides), carvacrol (C. murale), and carvacrol (C. album) with concentrations of 8.87%, 10.64%, and 8.43%, respectively. Notably, C. ambrosioides and C. murale demonstrated the strongest inhibitory effects, followed by C. album suggested to be used as herbicide treatments in the future. Chenopodium species exert significant inhibitory effects by releasing allelochemicals against several tested species. Therefore, allelopathy appears to be responsible for the nearby plant structure through the action of their bioactive metabolites.

Essential oil formulation of Thymus capitatus L. (wild and cultivated thyme) and Majorana hortensis L. (marjoram) were investigated for allelopathic activity against Convolvulus arvensis and Setaria viridis seeds and seedling growth. Thymol, camphor, carvacrol, thujone, ä-terpinene, borneol, p-cymene, carvacrol, 1, 8-cineole, caryophyllene oxide, á-humulene á-pinene, borneol, â-pinene, caryophyllene, caryophyllene oxide, linalol and phellandrene were detected by GC-Ms analysis from the oil contents. Macroemulsion (Mac-E) and nanoemulsion (Nano-E) were formulated from oil by adding co-surfactant and surfactant. These formulations were subjected to stability stresses and were tested for herbicidal activity against C. arvensis seeds germination and seedling growth. Nanoemulsion had particle size of 5.3, 12.0 and 22.1 nm for M. hortensis, T. capitatus wild and T. capitatus cultivated, respectively. Depending on ED50 M. hortensis (oils, Mac-E and Nano-E) exhibited strong allelopathic activity on C. arvensis, however, the lowest activity was achieved from T. capitatus cultivated followed by T. capitatus wild. The Nano-E exhibited pronounced post-emergence properties on (5–7 leaves stage) than others formulation on C. arvensis in greenhouse conditions.