Abstract
Soil salinization and alkalization always co-occur in grassland ecosystem, but little information exists concerning the mixed effects of salt-alkaline stresses on plants. Leymus chinensis is considered as one of the most promising grass species in Songnen Grassland of Northern China. In this study, we investigated the effects of 30 mixed salt-alkaline conditions (NaCl, Na 2 SO 4 , NaHCO 3 and Na 2 CO 3 ; pH 7.10-10.18 and salinity 50-250 mM) on seed germination and seedling growth of L. chinensis. The results showed that germination percentage and rate were both decreased with increasing salinity and pH. Nongerminated seeds germinated well after being transferred to distilled water from treatment groups. Shoot and radicle growth were also affacted by salinity, pH and their interactions. However, radicle length decreased more markedly with increasing salinity and pH, and was strongly inhibited when pH reached 8.05. Stepwise regression analysis results showed that salinity was the dominant factor for seed germination under mixed salt-alkaline stress conditions. However, once radicle break through the seed coat, and pH changed into the dominant factor for seedling establishment. These results indicated that mixed salt-alkaline stresses had different impacts on germination and early seedling stages of L. chinensis . A better understanding of the germination and seedling processes should facilitate the effective utilization of this species under such complex environment.
Highlights
Soil salinization and alkalization is a major environmental problem throughout the world, which limits growth and production of plant and results in land degradation
Germination of L. chinensis seeds was significantly affected by pH, salinity and their interactions of the two factors (p
In the other five treatment groups (A-E), Seedling growth test For evaluation of the effects of mixed salt-alkaline stresses on early seedling growth, seeds were incubated initially in distilled water at 30/20 °C with 12 h photoperiod, when the coleoptile had just emerged, 20 of the early seedlings were incubated with treatment solutions
Summary
Soil salinization and alkalization is a major environmental problem throughout the world, which limits growth and production of plant and results in land degradation. In Songnen Plains of Northeast China, approximately 70% of the natural grassland has been seriously degraded due to the impacts of salt and alkali soils, and this trend is still increasing (Zhang and Mu, 2009). The impact of salt stress involves osmotic and ionic effects, alkali stress has same stress factors but added the influence of high pH, which can inhibit ion uptake and disrupt ionic balance of plant cells (Munns, 2002; Yang et al, 2007). Salinization and alkalization always co-occur in nature conditions, plant survive under salt and alkaline stresses are very complex (Shi and Wang, 2005; Li et al, 2009). Mixed effect of salt stress and alkali stress should be further explored, that of salt stress or alkali stress
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