The Potentiality of Marine Macro-Algae as Bio-Fertilizers to Improve the Productivity and Salt Stress Tolerance of Canola (Brassica napus L.) Plants

The present study aimed to evaluate the potentiality of three seaweeds, which belong to different algal taxa (green alga Ulva lactuca Linnaeus, brown alga Cystoseira spp., and red alga Gelidium crinale (Hare ex Turner) Gaillon) as bio-fertilizers to improve the growth and yield of canola (Brassica napus L.) plants under greenhouse conditions. Furthermore, the impact of seaweeds in alleviating the effects of salt stress (75 and 150 mM NaCl) on canola plants was also investigated. The three examined seaweeds (applied as soil amendments) successfully alleviated the harmful effects of salinity on canola plants by significantly reducing the inhibition of chlorophyll a, b, total carbohydrate accumulation, and growth promoting hormones, while increasing antioxidative compounds, such as phenols, flavonoids, anthocyanin, and osmoprotectants, including total carbohydrates and proline. Phytochemical analysis of the three examined seaweeds suggests that their stimulatory effect on growth and productivity under normal and salinity growth conditions may be linked to their constituents of a wide variety of growth promotive hormones, including indole acetic acid, indole butyric acid, gibberellic acid, cytokinins, total carbohydrates, and phenolic compounds. U. lactuca was found to be the best candidate to be used as a bio-fertilizer to improve canola growth, yield, and salt stress tolerance.