Nanoceria seed priming enhanced salt tolerance in rapeseed through modulating ROS homeostasis and α-amylase activities

Background: Salinity is a big threat to agriculture by limiting crop production. Nanopriming (seed priming with nanomaterials) is an emerged approach to improve plant stress tolerance; however, our knowledge about the underlying mechanisms is limited. Results: Herein, we used cerium oxide nanoparticles (nanoceria) to prime rapeseeds and investigated the possible mechanisms behind nanoceria improved rapeseed salt tolerance. We synthesized and characterized polyacrylic acid coated nanoceria (PNC, 8.5 +/- 0.2 nm, -43.3 +/- 6.3 mV) and monitored its distribution in different tissues of the seed during the imbibition period (1, 3, 8 h priming). Our results showed that compared with the no nanoparticle control, PNC nanopriming improved germination rate (12%) and biomass (41%) in rapeseeds (Brassica napus) under salt stress (200 mM NaCl). During the priming hours, PNC were located mostly in the seed coat, nevertheless the intensity of PNC in cotyledon and radicle was increased alongside with the increase of priming hours. During the priming hours, the amount of the absorbed water (52%, 14%, 12% increase at 1, 3, 8 h priming, respectively) and the activities of a-amylase were significantly higher (175%, 309%, 295% increase at 1, 3, 8 h priming, respectively) in PNC treatment than the control. PNC primed rapeseeds showed significantly lower content of MDA, -H2O2, and O-.(2)- in both shoot and root than the control under salt stress. Also, under salt stress, PNC nanopriming enabled significantly higher -K+ retention (29%) and significantly lower -Na+ accumulation (18.5%) and -Na+/K+ ratio (37%) than the control. Conclusions: Our results suggested that besides the more absorbed water and higher alpha-amylase activities, PNC nanopriming improves salt tolerance in rapeseeds through alleviating oxidative damage and maintaining -Na+/K+ ratio. It adds more knowledge regarding the mechanisms underlying nanopriming improved plant salt tolerance.

Automated summary

The study demonstrated that nanopriming with cerium oxide nanoparticles improved salt tolerance in rapeseeds by enhancing germination, water absorption, alpha-amylase activities, reducing oxidative damage, and maintaining Na+/K+ ratio. The nanoparticles were mainly located in the seed coat during priming, with increasing intensity in cotyledon and radicle over time. This research provides insights into the mechanisms underlying nanopriming-enhanced plant salt tolerance.