Dynamics of the antioxidant system during seed osmopriming, post-priming germination, and seedling establishment in Spinach (Spinacia oleracea)

Osmopriming is a pre-sowing treatment that improves seed germination performance and stress tolerance. To understand osmopriming physiology, and its association with post-priming stress tolerance, we investigated the antioxidant system dynamics during three stages: during osmopriming, post-priming germination, and seedling establishment. Spinach seeds (Spinacia oleracea L. cv. Bloomsdale) were primed with −0.6 MPa PEG at 15 °C for 8 d, and dried at room temperature for 2 d. Unprimed and primed germinating seeds/seedlings were subjected to a chilling and desiccation stresses. Seed/seedling samples were collected for antioxidant assays and germination performance and stress tolerance were evaluated. Our data indicate that: (1) during osmopriming the transition of seeds from dry to germinating state represses the antioxidant pathways (residing in dry seeds) that involve CAT and SOD enzymes but stimulates another pathway (only detectable in imbibed seeds) involving APX; (2) a renewal of antioxidant system, possibly required by seedling establishment, occurs after roughly 5 d of germination; (3) osmopriming strengthens the antioxidant system and increases seed germination potential, resulting in an increased stress tolerance in germinating seeds. Osmopriming-mediated promotive effect on stress tolerance, however, may diminish in relatively older (e.g. ∼5-week) seedlings.

Research highlights▶ Osmopriming represses one of the antioxidant system pathways residing in dry spinach seeds but stimulates another one that is only detectable in imbibed seeds. ▶ This is reflected by reduced activities of CAT and SOD, and increased activity of APX. ▶ A renewal of antioxidant system, possibly required by seedling establishment, occurs during late germination (post ∼5-d). ▶ Osmopriming increases germination potential and stress tolerance in germinating seeds via bolstering the antioxidant system. ▶ Osmopriming-mediated promotive effect on stress tolerance diminishes during the seedling growth.