Biostimulant effect of Cladophora glomerata extract on garden cress plant growth

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.