Improvement of seed germination traits in canola (Brassica napus L.) as affected by saline and drought stresses

In many crop species, seed germination and early seedling growth are the most sensitive stages to stress. Salinity and drought may delay the onset, reduce the rate and increase the dispersion of germination events, leading to reductions in plant growth and final crop yield. The adverse effects of salt stress can be alleviated by various measures, including seed priming (pre-sowing seed treatment). The general purpose of seed priming is to partially hydrate the seed to a point where germination processes are begun but not completed. Most priming treatments involve imbibing seed with restricted amounts of water to allow sufficient hydration and advancement of metabolic processes but preventing germination or loss of desiccation tolerance. The objective of this study was to determine factors responsible for delayed germination and early seedling growth due to salt toxicity or osmotic effect and to optimize the best priming treatment for these stress conditions. In this experiment, treated seeds (control, KNO3 and hydropriming) of canola (Brassica napus L. cv. Okapi) were evaluated at germination and seedling growth stages for tolerance to salt (NaCl) and drought conditions (PEG-6000) at the same water potentials of 0.0, −3, −6, −9 and −12 bar. Electrical conductivity (EC) values of the NaCl solutions were 0, 3, 6, 9 and 12 dS.m−1, respectively. Results showed that germination delayed in both solutions, being variable with different priming treatments. Germination, and root and shoot length were higher, but mean germination time and unusual germination percentage were lower in NaCl than in PEG at the same water potential. Seeds were germinated at all concentrations of NaCl, but no seed germination was observed at −12 MPa of PEG treatments. NaCl had less inhibiting effect on the seedling growth than the germination. It was concluded that inhibition of germination at the same water potential of NaCl and PEG resulted from osmotic effect rather than salt toxicity. Hydro priming increased germination and seedling growth under salt and drought stresses.