Drought stress is a major abiotic stress, limiting crop production and yield. Overall, drought reduces flower number and size, also affecting the viability and durability of flowers. Thus, understanding its impacts has become a major aim for the sustainability of the horticultural industry. Calendula officinalis L. (pot marigold) is a widely used plant in the ornamental horticulture and also used in traditional medicine due to its wide range of secondary metabolites, flavonoids and carotenoids contents. Nevertheless, it is highly affected by drought, although some genotypes show some tolerance to water scarcity.

In this study, we compared the impacts of moderate and severe drought in four different pot marigold genotypes, evaluating its responses in photosynthetic pigments (chlorophylls and carotenoids), in the levels of proline and malondialdehyde in leaves and flowers, and in the enzymatic activity of catalase (CAT), peroxidase (POX), and ascorbate peroxidase (APX), as well as in the production of flowers.

Overall results showed a high resilience to moderate drought, although highly dependent on the genotypes evaluated. In contrast, severe drought had a harsh impact on most genotypes, especially in the production of flowers, despite the high activities of APX, CAT, and POX enzymes. These results also show that a considerable variation in drought tolerance occurs in pot marigolds that can be used to screen useful tolerance traits.