Ibtissem Ben Hammouda

Phytohormones, or plant hormones, are intrinsic organic compounds within plants. These compounds have a significant impact as essential plant growth and development regulators, influencing processes from seed germination to fruit ripening. The exogenous application of these phytohormones, such as gibberellic acid (GA₃), indole-3-acetic acid (IAA), and brassinosteroids, has been shown to significantly enhance horticultural productivity, with reported increases in germination, growth, and yield ranging from 10–40%. These signaling molecules are also vital for micro and macroalgae development and functioning. Recognizing their presence within algae presents a fresh perspective for horticultural researchers and cultivators, offering opportunities to enhance the quality and application of horticultural crops. Nevertheless, the challenge arises from the presence of phytohormones in trace amounts, complicating their extraction and identification. This paper will offer a comprehensive overview of phytohormone classification and detection methods and highlight their presence in algae, which may serve as an alternative for promoting plant growth in agriculture.

Propolis is a valuable natural product whose chemical composition and bioactivity are strongly dependent on its geographical and botanical origin. This study presents a comprehensive comparative analysis of the volatile profiles and antibacterial properties of propolis from Romania, Australia, and Uruguay, benchmarked against previously published data from samples from Poland and Turkey. Volatile compounds were profiled using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. The resulting data were interrogated using multivariate chemometric analyses (HCA, PCA), and antibacterial activity was assessed via the disk diffusion method against five bacterial strains. Chemometric analysis revealed a clear demarcation into two primary chemotypes: a European type (Poland, Romania, Turkey) dominated by aromatic compounds such as benzoic acid, and a non-European type (Australia, Uruguay) characterized by a high abundance of terpenes. The Australian propolis exhibited a complex terpene profile rich in α-copaene and pinenes, while the Uruguayan sample was distinguished by an exceptionally high concentration of α-pinene. All active extracts showed selective, concentration-dependent inhibition against Gram-positive Staphylococcus aureus and Streptococcus mutans. The terpene-rich Australian propolis displayed the highest antibacterial potency, particularly against S. mutans. Crucially, Pearson correlation analysis revealed a counter-intuitive relationship: the most abundant terpenes in the non-European samples (e.g., α-pinene, verbenone) were significantly negatively correlated with antibacterial activity (r ≈ −0.99). Conversely, less abundant compounds, including linalool and acetic acid, were identified as strong positive predictors of inhibition (r > 0.90). These findings underscore a complex geography-chemotype-bioactivity relationship, where the overall synergistic effect of a mixed chemical profile, rather than the dominance of a single compound, determines antibacterial potency. The initially proposed markers provide a basis for origin-based standardization and highlight Australian propolis as a promising source of natural antibacterial agents.

Biostimulants that improve agriculture's productivity and environmental responsibility are widely favored and used. Algae has emerged as a viable option for sustainable agriculture. In the present study, the effects of the Cladophora glomerata (L.) Kütz. aqueous extract in three concentrations (2.5, 5, and 10 mg extract per mL of tap water) was tested on the growth and productivity of garden cress (GCR) Lepidium sativum L., plants over 12 days, and the results were compared with those of the control group (irrigated only with tap water). The effect of the algae extract was studied by assessing the changes in phenolic compounds using HPLC–DAD and determining the chlorophyll content as well as the total antioxidant capacity of the GCR using DPPH and ABTS tests. Total phenolics, as well as total flavonoids, were measured. The potential role of algae extract in promoting cress plant growth was attained when compared to the control, mainly at a concentration of 2.5 mg/mL, which exhibited the highest yield growth after 12 days and presented the highest antioxidant capacity at 13.53 ± 1.16 mg Trolox equivalent (TE)/g dry weight (DW), compared to 10.44 ± 0.33 mgTE/g DW for the control. The total phenolic content significantly increased (p < 0.05) from 14.34 ± 0.84 mg gallic acid equivalent (GAE)/ g dry weight (DW) to 23.14 ± 0.55 mg GAE/g DW. Eleven phenolic compounds were identified in different tested samples of GCR, whether treated or not treated with algae extracts. Chrysin was only identified in the treated plants. Therefore, the use of algae (C. glomerata) presents promising potential as a biostimulant in agriculture, contributing to increased plant growth and improved resistance to environmental stress.