The role of oxidative stress in seed priming to improve germination and vigour

Seed priming improves germination, but responses vary with procedure and plant used, potentially from differential responses in oxidative pathways. This study targeted oxidative pathways in seed priming, using hydrogen peroxide (H2O2), antioxidant-related micronutrients (Zn, Se and Mn), or a combination, to modulate germination and plant growth characteristics of hemp and barley. Hemp tolerated higher H2O2 (1 M vs 0.125 M) and micronutrients (6-fold greater) concentrations than barley, with the combination treatment significantly increasing hemp germination but decreasing barley germination. Seed priming did not improve hemp germination under salt stress (200 mM NaCl), but the micronutrient treatment improved germination of barley under salt stress (100 mM NaCl). Histological staining showed that micronutrient-primed root tips accumulated less O2- in both non-stressed and salt-stressed conditions. We assessed seed priming benefits if grown in soil by measuring plant quality in three-week-old plants potted post-priming, but most quality factors were not significantly improved, except barley where shoot zinc content increased. In summary, seed priming with H2O2 and/or micronutrients increased germination in hemp, but only micronutrients increased barley germination. Future work will continue optimising the priming methodology and further investigate the role of oxidative stress in the observed responses.