Effect of several commercial seaweed extracts in the mitigation of iron chlorosis of tomato plants (Solanum lycopersicum L.)

Commercial seaweed extracts (SWEs) have been applied in agriculture for ameliorating biotic and abiotic stress in plants. However, the mechanisms of action of these extracts are only partially known. Most of the research work with SWEs has focused on abiotic stresses such as drought, salinity or high temperatures, but little is known about SWE effects on plants with nutrient imbalances. Therefore, the goal of this study was to investigate the effects of several commercial SWEs (based on Ascophyllum nodosum and Durvillea potatorum) in the mitigation of iron chlorosis of stressed tomato plants. Tomato plants were grown in a hydroponic system initially with Fe, and then Fe was removed from the nutrient solution. SWEs were applied twice, first during the growth period (+Fe) and second at the beginning of Fe deficiency (-Fe), following the recommended doses of manufacturers. Some of SWE treatments activated the antioxidant system in Fe-deficient tomato plants increasing SOD and CAT activity. However, SWEs application did not produce positive effects on biomass, chlorophyll content, activation of Fe acquisition strategies and Fe uptake with respect to the untreated control.