Mechanistic insights into enhanced tolerance of early growth of alfalfa (Medicago sativa L.) under low water potential by seed-priming with ascorbic acid or polyethylene glycol solution

Abstract

Poor establishment of early seedlings due to water stress is a serious problem that decreases crop growth and final yield. In current study, the potential of seed-priming with ascorbic acid (AsA) or polyethylene glycol (PEG) solution in increasing growth and improving water stress tolerance in early seedlings of alfalfa (Medicago sativa L.) that has both agricultural and medicinal values was evaluated. Under normal conditions, both two solutions improved the growth of early seedlings which might be associated with the ability to increase soluble sugars, proline, total phenolics, and the activities of antioxidant enzymes, as well as to decrease basal amounts of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in the seedlings. In non-primed seedlings, the growth of early seedlings decreased under water stress, and the principle component analysis (PCA) indicated that H2O2 and MDA accumulations were closely associated with the decreased growth of early seedlings. Seed-priming with AsA or PEG solution significantly ameliorated the detrimental impacts of water stress on early seedling growth, and results of PCA supported that the improvement in growth parameters under water stress might be ascribed to lower accumulations of H2O2 and MDA, higher accumulations of proline, soluble sugars, total soluble proteins, and total phenolics as well as increased activities of H2O2-scavenging enzymes. Furthermore, our data indicated that the amelioration effectiveness of both AsA and PEG solutions on early seedling growth under non-stressed and water-stressed conditions was comparable. Taken together, our findings suggest that seed-priming with AsA or PEG solution could equally be effective in improving early seedling growth of alfalfa under both non-stressed and water-stressed conditions.