Effect of salicylic acid and sodium nitroprusside on growth parameters, photosynthetic pigments and secondary metabolites of safflower under drought stress

The effect of drought stress on the production of secondary metabolites and photosynthetic pigments in safflower, Carthamus tinctorius L., was studied in the present work. The application of two regulating signaling molecules of salicylic acid (SA) and sodium nitroprusside (SNP) were respectively examined at concentrations of 250 pM and 25 pM on the plants subjected to different field capacity (FC) volumes of water (25% and 100%). The drought stress decreased the leaf number and area, shoot fresh and dry weights, and shoot length, whereas the root length and fresh weight were increased. There was an increase in the secondary metabolites (flavonoids, anthocyanin, phenol, and phenylalanine ammonia lyase activity) and a decrease in photosynthetic pigments. The SA treatment improved the rate of photosynthesis, anthocyanin content, and phenylalanine ammonia lyase activity. The SNP treatment improved the growth of aerial parts and hindered the root elongation possibly because of their free radical scavenging ability. The drought stress can be applied for enhanced production of secondary metabolites and the simultaneous administration of SA and SNP can be proposed as a mitigation strategy to reserve the normal plant function.