Priming with sodium nitroprusside and hydrogen peroxide increases cotton seed tolerance to salinity and water deficit during seed germination and seedling development

A major difficulty in cotton crops is high-quality seed production, which interferes with plant vigor and estab-lishment. Techniques such as seed physiological conditioning have been reported due to their ability to improve stress tolerance in seeds and plants. Considering this, we carried out this research to evaluate the use of signaling molecules to increase cotton plant stress tolerance. Seeds were conditioned on aerated solutions of indoleacetic acid (100 mu M), hydrogen peroxide (100 mu M), chitosan (0.75 mM), melatonin (0.2 mM), sodium nitroprusside (100 mu M), and pure water (hydropriming), at 20 degrees C for 24 h. Then seeds were washed with running water and dried in an oven with forced air circulation at 25 degrees C for 24 h. Treated seeds or nontreated seeds were placed to germinate under salinity (10 dS m-1 NaCl) and water deficit by using polyethylene glycol (PEG 6000) at -0.6 MPa, and with nonstressed condition (water). The solutions mentioned were used to moisten the Germitest (R) paper roll at 2.5 times its weight. We also analyzed the activity of the enzymes superoxide dismutase, catalase, and ascorbate peroxidase, as well as the content of proline, hydrogen peroxide, and lipid peroxidation. Physi-ological conditioning with signaling molecules effectively improved cotton seed germination under stress, especially to hydrogen peroxide and sodium nitroprusside, which resulted in better performance on the pa-rameters of germination and seedling growth. As stress conditions induced oxidative stress, as observed by lipid peroxidation, we found that physiological conditioning improved the seed antioxidant system, with hydrogen peroxide and sodium nitroprusside resulting in better performance. Our results highlighted the potential of so-dium nitroprusside and hydrogen peroxide as inducers of stress tolerance in cotton.