Seed Osmolyte Priming and Abiotic Stress Tolerance

Abstract

Seed priming has been used to achieve enhanced and uniform emergence of many horticultural crops. Controlled seed rehydration induced by priming triggers metabolic processes associated with early stages of germination. Compounds employed in priming can be large and charged, such as hormones or acidic molecules, or small and neutral osmolytes such as sugars and polyols. Priming with water, osmolytes such as proline or mannitol, hormones such as gibberellin or brassinosteroids, or biological solutions such as salicylic acid or essential oils can enhance seedling or mature-plant tolerance to abiotic stresses. The treatment effectiveness may depend on methodology, crop, and/or seed structure. Beneficial effects of priming for abiotic stress tolerance are often associated with enhanced antioxidant activity in the seedling, as expressed by increased enzyme activity and/or concentrations of protective compounds. Although the beneficial effects of seed priming can be significant, they are not observed consistently. This may be related to the duration of the protective action of priming. Protection afforded by priming is often more effective if stress is present at the time of sowing, germination, or emergence. Delaying sowing after priming can result in impaired germination, while protective effects of the treatment do not always persist with plant maturation. Future research on seed priming for abiotic stress resistance should emphasize development of treatments that are effective even after treated seeds are stored, persist during most or all of plant maturation, and behave similarly in different cultivars of the same crop and ideally in a range of crops.