Physiological and biochemical analysis of seed priming effect on Brachypodium distachyon under abiotic stress

Plant breeders and scientists try to develop more precise solutions for the production of new varieties, which are more resistant to abiotic stress to supply the food and feed demand of the growing world population. Seed priming is a hydration technique by treating seeds with various chemicals to activate the metabolism of the plant prior to sowing. For many years, seed priming has been used to achieve synchronized germination and increased germination rate. However, in recent years, studies have focused on the effect of seed priming on the plant's defense mechanism against abiotic stress. Brachypodium distachyon is a model plant for important cereals such as barley, wheat and rye that have great importance as food and feed supply. In this study, B. distachyon (Bd-21 line) seeds were treated with distilled water for hydropriming, potassium nitrate (1, 2, 3 per cent KNO3) for osmopriming, and salicylic acid (0.25, 0.5, 0.75 mM SA) for hormonal priming to investigate the effect of seed priming on germination parameters and evaluate the physiological and biochemical changes caused by different priming methods in B. distachyon plants under salt and drought stress. The germination test showed that all priming methods had a positive effect on seed germination parameters, in particular, mean emergence time (MGT), germination index (GI), uncertainty of germination (U) and synchronization (Z). Morphological characteristics of plants such as biomass and plant height were positively affected by hydropriming and low concentrations of KNO3. Relative water content (RWC) and chlorophyll concentration decreased while proline content and relative membrane permeability (RMP) increased under salt and drought stress. Antioxidant levels (catalase-CAT, peroxidase-POD and superoxide dismutase-SOD) showed extensive variation and significant differences among priming treatments. Overall, it can be concluded that osmopriming with 1 per cent KNO3 would be preferable for drought and salt stress tolerance in B. distachyon. To our knowledge, seed priming was performed for the first time in B. distachyon with this study. Therefore, the results of this study can further be used in omics studies to explore the molecular mechanisms underlying abiotic stress tolerance of B. distachyon and other cereal grains after seed priming