Characterization of Exogenous Nitric Oxide Effect on Crocus sativus Response to Different Irrigation Regimes

Water scarcity is one of the main factors limiting crop production worldwide. The study on response of saffron to irrigation regime showed that one-time irrigation at field capacity of 100% resulted in the greatest number and weight of flower, and dry stigma yield, but weekly irrigation regime at the same conditions prevented flowering process. One-time irrigation regime reduced water potential (Ψw) of plants, while the contents of chlorophylls, carotenoid, anthocyanin, carbohydrates, phenol, amino acid, proline, H2O2, and the activity of antioxidant enzymes in the one-time irrigated plants were higher than in the weekly irrigated plants. The nitric oxide (NO) donor, sodium nitroprusside (SNP), significantly increased photosynthetic and non-photosynthetic pigments, metabolites, and antioxidants in both irrigation regimes, with the highest content in the one-time irrigated plants. The SNP treatment increased the flower yield in the one-time irrigated plants, but it could not induce flowering in the weekly irrigated plants. Collectively, these results demonstrated the importance of irrigation regime in flower induction in saffron. Even though the exogenous SNP improved the performance of saffron, it could not overcome the importance of irrigation frequency regime on flowering process. Overall, the SNP application accompanied with the one-time irrigation regime provided higher flower yield and improved the physiological performance of saffron plant.