Abstract
Spermidine (Spd) is known to protect macromolecules involved in physiological and biochemical processes in plants. However, it is possible that Spd also plays an osmotic regulatory role in promoting the seed germination of Leymus chinensis (L. chinensis) under salt-alkali stress. To investigate this further, seeds of L. chinensis were soaked in Spd solution or distilled water, and a culture experiment was performed by sowing the soaked seeds in saline-alkaline soils. The data showed that the Spd priming resulted in an increase of more than 50% in soluble sugar content and an increase of more than 30% in proline content in the germinating seeds. In addition, the Spd priming resulted in an increase of more than 30% in catalase activity and an increase of more than 25% in peroxidase activity in the germinating seeds and effectively mitigated the oxidative damage to the plasma membrane in the germinating seeds under salt-alkali stress. Moreover, the Spd priming of seeds affected the accumulation of polyamine (PA) and maintained the activities of macromolecules involved in physiological metabolism in germinating seeds exposed to salt-alkali stress. Furthermore, the Spd priming treatment increased the hydrogen peroxide (H2O2) level to more than 30% and the Ca2+ concentration to more than 20% in the germinating seeds, thus breaking the dormancy induction pathways in L. chinensis seeds through beneficial hormone enrichment. This study provides an insight into the Spd-mediated regulation pathway during exogenous Spd priming of L. chinensis seeds, which mitigates osmotic and oxidative damage and maintains the integrality of the cell lipid membrane. Thus, exogenous Spd priming increases PA oxidase activity and maintains the accumulation of H2O2. We found that the H2O2 beneficially affected the balance of Ca2+ and hormones, promoting the vigor and germination of L. chinensis in response to salt-alkali stress.
Highlights
Soils with high salinity and alkalinity commonly contain high levels of Na2CO3 and NaHCO3, affecting plant growth and development due to salinization damage (Parihar et al, 2015)
To explore whether Spd priming plays a regulatory role in improving the germination of L. chinensis seeds under salt-alkali stress, a series of responsive changes in physiological and biochemical indicators in L. chinensis seeds were measured after 12 h of Spd soaking
The germination rates of L. chinensis seeds after the Spd priming treatment were increased by 33.66% compared to those in the control seeds treated with distilled water (Figure 2B)
Summary
Soils with high salinity and alkalinity commonly contain high levels of Na2CO3 and NaHCO3, affecting plant growth and development due to salinization damage (Parihar et al, 2015). Tzvel., one of the most important grassland plants in the Songnen Plain, is a perennial rhizomatous species of the Poaceae family containing high levels of proteins, mineral nutrients, and carbohydrates (Lin et al, 2016). The mature seedlings of L. chinensis have a strong tolerance to saltalkali stress and are the most promising gramineous plant for the rehabilitation of grassland vegetation in soils with salinizationalkalization (Li et al, 2018). The low germination rate of L. chinensis has been a potential obstacle to its propagation and utility in restoring grassland vegetation in soils with high salinity-alkalinity. Promoting the germination rates and seedling growth of L. chinensis in saline-alkaline soils is important for enhancing the propagation of this grass species to restore the soil ecological balance
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