Seed Priming Strategies for Abiotic Stress Tolerance in Plants: Mechanisms, Comparative Evidence and Practical Limitations

Abstract

Seed priming is a pre-sowing intervention intended to improve germination behaviour, seedling establishment and, under suitable conditions, subsequent tolerance to environmental stress. The approach typically allows limited hydration and metabolic activation without radicle emergence, followed by controlled drying, although some biological and physical pretreatments follow different protocols. This narrative review evaluates water-based, osmotic, salt, hormonal, chemical, microbial, botanical, radiation, magnetic and nanoparticle-mediated strategies for mitigating salinity, drought, temperature extremes and potentially toxic elements. Evidence from peer-reviewed experimental studies indicates that selected protocols can enhance germination, antioxidant regulation, ionic adjustment, photosynthetic performance and early growth, but responses vary with seed quality, genotype, dose, exposure duration and stress severity. Mechanistic associations should not always be interpreted as proof of causation, and benefits observed in controlled environments cannot be assumed to translate into stable field yields. Distinctions between seed treatments and foliar or root priming are especially important when evaluating hormonal and redox studies. Nanopriming and physical techniques offer research opportunities while raising additional questions about reproducibility, exposure control and safety. Comparative evidence supports prioritising protocol-specific optimisation, appropriate unprimed and vehicle-treated controls, post-treatment storability, agronomic validation and cost-effectiveness. Seed priming is best regarded as a complementary and context-dependent component of crop establishment rather than a universal solution to abiotic stress.