HO seed priming improves tolerance to salinity; drought and their combined effect more than mannitol in Cakile maritima when compared to Eutrema salsugineum.

The effect of HO and mannitol seed priming was investigated on plant growth, oxidative stress biomarkers and activities of antioxidant enzymes in leaves of Cakile maritima and Eutrema salsugineum, when exposed to drought and salt stress, either separately applied or combined. Under unprimed conditions, drought severely restricted growth (40% as compared to the control) and redox balance of C. maritima seedlings, whereas E. salsugineum showed these drastic effects under individual salinity (33% as compared to the control). Combined salinity and drought maintained and even stimulated the antioxidant defense of both plants from unprimed seeds. Both priming agents (mannitol and HO) significantly ameliorated growth and antioxidant defense of both species grown under salinity, drought and their combined effect. However, HO priming appeared to be more beneficial in C. maritima seedlings. Indeed, oxidative injuries were significantly reduced, together with significantly higher concentrations of ascorbic acid (36%), glutathione (2-fold) and proline production (2-fold), leading to a greater redox balance that was closely associated with enhanced antioxidant enzyme activities, specifically under salt stress. Overall, our results indicate that it is very likely that HO priming, due to its signal role, improves C. maritima tolerance to both osmotic stresses and enables the plant to memorize and to decode early signals that are rapidly activated when plants are later exposed to stress.