“Nitric oxide boosts antioxidant defense in olive trees against unexpected temperature drops”

Nitric oxide (NO), a critical signaling molecule, holds significant potential for enhancing plant responses, especially under environmental stresses associated with modern climate changes. Sodium nitroprusside (SNP), an NO donor, has shown promising effects in this regard. To investigate the role of NO in increasing freezing stress tolerance in olive trees, plants were treated with varying concentrations of SNP (0 μM as control, 100 μM, and 200 μM) and then subjected to freezing temperatures of -1, -3, and -6 °C. 100 μM SNP concentration yielded the most notable benefits, with efficacy dependent on stress severity. Treatment with 100 μM SNP enhanced the activity of antioxidant enzymes such as CAT, SOD, POX, and APX and significantly increased non-enzymatic antioxidant levels, including total phenols, flavonoids, flavonols, and anthocyanins. These enhancements reached up to 48.48 % at -1 °C, 21.8 % at -3 °C, 51.78 % at -6 °C, and 42.6 % under control conditions. SNP-treated olive plants also exhibited improved levels of photosynthetic pigments and chlorophyll precursors, indicating a positive influence of NO on photosynthetic processes. Furthermore, 100 μM SNP administration promoted osmotic regulation, evidenced by a 96.28 % increase in proline content and changes in total soluble sugars. These adaptive responses contributed to reduced H₂O₂ content, MDA levels, electrolyte leakage, and increased leaf longevity, highlighting SNP's role in enhancing membrane stability and overall plant vitality. The findings underscore NO's multifaceted role in modulating key physiological and metabolic processes that support olive tree resilience under low-temperature stress.