Effects of salinity on the antioxidant response of marigold flowers (Tagetes L.)

Salinization is an increasing problem worldwide, limiting crop production. Soil salinity causes ion toxicity, osmotic stress, nutrient deficiency and oxidative stress on plants, leading to the overproduction of reactive oxygen species (ROS). To counterbalance these effects, plants activate a complex detoxification system through the action of antioxidant pigments, carotenoids, phenolics and flavonoids, and the accumulation of minerals, that play an important role in human health against several diseases.

In this study, we investigated the impacts of salinity (0, 50, 100, 300 mM NaCl) on the flowers of three Tagetes patula cultivars harvested after 14 days, recording total carotenoids, minerals, carotenoids, ascorbic acid, total polyphenol content, and total flavonoid content. Results showed an overall increase in all compounds with the increase in salinity levels, in comparison with control conditions. Nevertheless, salinity (most especially 100 and 300 mM) strongly affected plant size and flower production.

Results showed that edible marigold flowers are a promising crop with enriched nutritional contents and antioxidant activity that can be a new source of source of nutraceuticals. However, this study also reports, for the first time, the harsh effects of high salinity in the production of flowers, limiting its production in high-salinity soils. We recommend its production in a short exposure to salinity up to 100mM NaCl to achieve a high production of nutraceuticals without compromising the viability of flower production.