Salicylic acid and boric acid improve flower growth, yield, and cold tolerance in French marigold (Tagetes patula)

A decrease in air temperature harms many ornamental plants, especially flowers grown in green space. To prevent cold stress, various elicitors are used that reduce the harmful effects of low temperature. Therefore, in this study, we investigated the impact of two elicitor's salicylic acid and boric acid on the growth and yield parameters of French marigold (Tagetes patula). Next, these plants were exposed to cold stress, and their physiological and morphological traits were also studied. Results showed that the application of elicitors, especially in higher concentrations, had a positive effect on morphological and physiological traits. Interaction of SA×BA with a concentration of 2mM, increased flower diameter (20%), stem height (19%), stem and root fresh weight (27 and 35% respectively), stem and root dry weight (31 and 39% respectively), and flower quality (26%). Also, the interaction of these two elicitors led to a decrease in ion leakage (22%), malondialdehyde (28%), and proline (24%) content, and an increase in chlorophyll fluorescence (28%), catalase (20%) and ascorbate peroxidase (33%) activity. In general, the application of salicylic acid and boric acid interaction treatment with 2mM concentration improved growth and yield characteristics and cold stress tolerance in French marigold.