Email: Wenshan Guo guows@yzu.edu.cn

Germination is a crucial process in the life span of plants and is one of the stages most sensitive to salinity stress. Numerous physiological mechanisms and multistage processes were found to be involved in it. In this study, the impact of salt stress on wheat germination was investigated, in terms of water uptake, ion accumulation, hormonal balance, and reserve utilization. When salt stress occurs, excessive Na+ accumulates in plants, accompanied by K+ extrusion.

The ABA content increased while GA3 decreased, and -amylase and cysteine protease activities were inhibited leading to a decrease in soluble sugar and protein content. Correlation analysis indicated that water uptake rate (WUR) was found to have a significant positive correlation with seed vigor index, Na+ and K+ contents. Salt-tolerant variety had higher Na+ and K+ contents and TaNHX1 and TaAKT1-like expression.

We concluded that water is the main limiting factor for germination under salt stress, soluble sugar was mainly used as an osmotic adjustment substance, showing an upward trend of its content after salt treatment at 48-72h while declining under control. Besides, Na+ and K+ can be used as an osmotic to facilitate water uptake instead of suffering from ion toxicity, which benefits from Na+ sequestration and K+ retention.

Meanwhile, -amylase activity was found to have a significant positive relationship with germination rate, GA3, soluble sugar content and K/Na. Besides, there was a significant positive correlation between K/Na and soluble sugar content while GA3/ABA showed a significant positive correction with WUR. Transcriptome results showed that starch and sucrose metabolism was the most enriched pathway, and six genes related to -amylase activity were annotated.

These results indicated that -amylase activity was the key to germination under salt stress, K/Na homeostasis and GA3/ABA balance contributes to starch metabolism and water uptake by maintaining high -amylase activity.