In this study, we aim to explore the allelochemicals of marine brown algae Sargassum fusiforme and the mechanism of allelopathy effect on Heterosigma akashiwo. Six potential allelopathic substances, palmitic acid, arachidonic acid, α-linolenic acid (ALA), fucosterol, 24-hydroperoxy-24-vinylcholesterol, and saringosterowere, were isolated and identified from S. fusiforme by column chromatography, NMR, TOF-MS and GC‐MS analyses. The ALA and 24-hydroperoxy-24-vinylcholesterol showed remarkable inhibitory activities on H. akashiwo growth. Besides, the allelopathic mechanism between the ALA and H. akashiwo was preliminarily investigated. The results indicated that the activities of SOD and POD of H. akashiwo gradually decreased under high ALA concentration. The reduction of photosynthetic pigments and chlorophyll fluorescence parameters, as well as apparent electron transport rate in H. akashiwo cells, aggravated gradually with increasing the concentration of the ALA. In summary, this study revealed the responses of morphology and physiology of H. akashiwo when exposed by ALA, while revealing the potential of macroalgae in red tide control.

A soil microcosm study was performed to examine the impacts of cerium oxide nanoparticles (nCeO₂) on the physiology, productivity, and macromolecular composition of barley (Hordeum vulgare L.). The plants were cultivated in soil treated with nCeO₂ at 0, 125, 250, and 500 mg kg⁻¹ (control, nCeO₂-L, nCeO₂-M, and nCeO₂-H, respectively). Accumulation of Ce in leaves/grains and its effects on plant stress and nutrient loading were analyzed. The data revealed that nCeO₂-H promoted plant development resulting in 331 % increase in shoot biomass compared with the control. nCeO₂ treatment modified the stress levels in leaves without apparent signs of toxicity. However, plants exposed to nCeO₂-H treatment did not form grains. Compared with control, nCeO₂-M enhanced grain Ce accumulation by as much as 294 % which was accompanied by remarkable increases in P, K, Ca, Mg, S, Fe, Zn, Cu, and Al. Likewise, nCeO₂-M enhanced the methionine, aspartic acid, threonine, tyrosine, arginine, and linolenic acid contents in the grains by up to 617, 31, 58, 141, 378, and 2.47 % respectively, compared with the rest of the treatments. The findings illustrate the beneficial and harmful effects of nanoceria in barley.

Biodiesel wash water is a contaminating industrial effluent that must be treated prior to disposal. The use of this effluent as a low-cost alternative cultivation medium for microalgae could represent a viable supplementary treatment. We cultivated 11 microalgae species with potential use for biodiesel production to assess their growth capacities in biodiesel industrial washing waters. Only Monoraphidium contortum, Ankistrodesmus sp., Chlorococcum sp., and one unidentified Chlorophyceae species grew effectively in that effluent. M. contortum showed the highest growth capacity and had the second highest fatty acid content (267.9 mg g⁻¹ of DW), predominantly producing palmitic (20.9%), 7,10,13-hexadecatrienoic (14%), oleic (16.2%), linoleic (10.5%), and linolenic acids (23.2%). In the second phase of the experiment, the microalgae were cultivated in biodiesel wash water at 75% of its initial concentration as well as in WC (control) medium. After 21 days of cultivation, 25.8 and 7.2% of the effluent nitrate and phosphate were removed, respectively, and the chemical oxygen demand was diminished by 31.2%. These results suggest the possibility of cultivating biodiesel producing microalgae in industrial wash water effluents.

Interest in use of flax (Linum usitatissimum L.) as cadmium (Cd)-accumulating plant for phytoextraction of contaminated soils opened up a new and promising avenue toward improving tolerance of its varieties and cultivars to Cd stress. The aim of this study is to get insights into the mechanisms of Cd detoxification in cell membranes, by exploring the effects of salicylic acid (SA)-induced priming on fatty acids and lipid composition of flax plantlets, grown for 10 days with 50 and 100 μM Cd. At leaf level, levels of monogalactosyldiacylglycerol (MGDG), phosphatidylcholine (PC), phosphatidylglycerol (PG), and neutral lipids (NL) have shifted significantly in flax plantlets exposed to toxic CdCl₂concentrations, as compared to that of the control. At 100 μM Cd, the linoleic acid (C18:2) decreases mainly in digalactosyldiacylglycerol (DGDG) and all phospholipid species, while linolenic acid (C18:3) declines mostly in MGDG and NL. Conversely, at the highest concentration of the metal, SA significantly enhances the levels of MGDG, PG and phosphatidic acid (PA), and polyunsaturated fatty acids mainly C18:2 and C18:3. Furthermore, SA pretreatment seems to reduce the Cd-induced alterations in both plastidial and extraplastidial lipid classes, but preferentially preserves the plastidial lipids by acquiring higher levels of polyunsaturated fatty acids. These results suggest that flax plantlets pretreated with SA exhibits more stability of their membranes under Cd-stress conditions.