Effect of Varied Salinity on Marigold Flowers: Reduced Size and Quantity Despite Enhanced Antioxidant Activity

Abstract

Salinity is an increasing problem worldwide that limits crop production. The cultivation of salt-tolerant flowers is a potential sustainable strategy for the exploitation of saline soils while avoiding the use of freshwater resources. However, our understanding of how flowers can adapt to salinity is still limited. In this study, we investigated the effects of salinity on a widely-used ornamental plant (Tagetes patula) by submitting three cultivars (cv. Aurora Orange, Fireball, Safari Scarlet) to different salinity levels (0, 50, 100, 300 mM). The plants were grown under controlled conditions and followed over two weeks. We tested the effect of salinity on plant growth and flower production, as well as on the levels of total carotenoids, polyphenols, and flavonoids, and the activities of antioxidant enzymes (catalase, peroxidase activity, ascorbate peroxidase). The findings indicate a substantial decline in both plant growth and flower production under saline conditions. Overall, plant height was ¼ lower, and there were 1/3 less flowers under salinity. Additionally, there was a consistent rise in antioxidant compounds, highlighting the swift response of defense mechanisms, both enzymatic and non-enzymatic, to combat stress. The high levels of antioxidant compounds sustain the use of marigold flowers as a new source of nutritional compounds, with enriched nutritional contents. Yet, cultivation of these plants in saline conditions should carefully consider the pronounced adverse effects observed at high salinity levels (e.g., 100 and 300 mM) on both plant and flower production.