Priming Seeds and Plants with Microbial Inoculants to Improve Growth and Stress Memory

Stress induces changes in plant's physiological functions, which leads to lower plant growth and agricultural yield. Seed priming is a novel, yet simple technique that involves the use of beneficial and eco-friendly biological agents to improve the physiological functioning of seeds. An understanding of the mechanisms involved in seed bio-priming with plant growth-promoting microbes is very crucial to efficiently utilize this technique towards agricultural sustainability. By triggering dormant stress response pathways, microbial priming improves a plant's ability to defend itself and produces a quicker or more powerful response to subsequent stresses. This help plants 'remember' and react more skillfully to recurring environmental stressors by enhancing their stress memory. It is generally thought that the advancement of metabolic processes along with activation of repairing systems during the pre-germination stage are the central reasons behind growth promotion and acquired stress tolerance. The application of plant growth-promoting rhizobacteria in agriculture has been emerging to improve stress resilience, widely used by seed technologists to enhance seed vigor in terms of germination potential and increased stress tolerance. The critical stages during the growth of crops are the uniform seed germination, early seedling growth, and uniform plant stand. The primed seeds show faster and uniform seed germination due to different enzyme activation, metabolic activities, biochemical processes of cell repair, protein synthesis, and improvement of the antioxidant defense system as compared to unprimed seeds. Seed priming has proved to be an effective method in imparting stress tolerance to plants using natural and/or synthetic compounds to treat the seeds before germination.