Elicitation with CaCl_₂ and SNP enhance antioxidant defense and regulate transcriptional changes in drought-stressed...

Calcium chloride and sodium nitroprusside mitigate PEG-induced drought in saffron by enhancing antioxidant defense, osmolyte levels, and stress-responsive genes expression, promoting resilience and adaptive growth. While calcium ions (Ca²⁺) and nitric oxide (NO), are key signalling mediators, which enhance plant's ability to survive abiotic stress, their definitive role in enhancement of drought tolerance in saffron is not fully studied yet. We aim to examine the effect of different concentration of calcium chloride (CaCl_₂) (25, 50, 75 mM) and sodium nitroprusside (SNP) (25, 50, 100 µM) on saffron cultured on MS media containing 10% polyethylene glycol (PEG) for 30 days. Results showed plants exposed to drought produced ROS (H₂O₂) that caused oxidative damage to the cells such as membrane damage. Moreover, drought has reduced biomass accumulation, relative water content, and photosynthetic pigment. Elicitor treatment significantly alleviated these effects, with 50 mM CaCl_₂ improving relative water content by 84% and 25 µM SNP enhancing biomass by 72% over drought-stressed plants. Both elicitors restored chlorophyll and carotenoid levels, reduced electrolyte leakage, enhanced antioxidant enzyme activities (SOD, POD), increased proline and phenolic contents, and improved total antioxidant capacity. Furthermore, expression of drought-responsive genes (DREB1,2, AREB1, SnRK2, NAC1, MYB37, bZIP23, DHN1) was upregulated under elicitor treatment. These findings highlight that CaCl_₂ and SNP have potential to support plant growth and development and to minimize the detrimental effect of drought stress on saffron.