Hydro-priming increases seed germination and early seedling growth in two cultivars of Napa cabbage (Brassica rapa subsp. pekinensis) grown under salt stress

To assess the effects of hydro-priming on enhancing germination and seedling growth in Napa cabbage (Brassica rapa subsp. pekinensis) under salt stress, seeds of two Napa cabbage cultivars that differed in salt tolerance, ‘Lainong 50’ (salt-tolerant) and ‘Xiaoza-56’ (salt-sensitive), were soaked in distilled water at 20°C in the dark for 10 h. Hydro-primed and non-primed seeds were then germinated under six levels of salinity (0, 50, 100, 150, 200, or 250 mM NaCl) under laboratory conditions. Various germination traits (e.g., germination percentages, germination potential, and seedling vigour index), anti-oxidant enzyme catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD)] activities, and proline and malondialdehyde (MDA) concentrations were then measured in 7-d-old seedlings. The results showed that salt-stress decreased seed germination traits and reduced early seedling growth in both Napa cabbage cultivars. Hydro-priming increased the seed germination percentages and early seedling growth in both cultivars grown under salt stress. These effects were significantly positively correlated with the activities of POD and CAT, and the accumulation of proline, which can alleviate oxidative membrane damage and result in decreased MDA concentrations. These findings suggest that hydro-priming is an effective method to increase seed germination percentages, germination potential, and early seedling growth in Napa cabbage grown under salt stress.