Format: ORAL

Hongxiang Zhang

1 Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China 2 Royal Botanic Gardens Victoria, Melbourne, Australia

Salinization is a serous agricultural and environmental problem worldwide that impacts crop production and natural ecosystems. Germination and seedling establishment is the prerequisite for species growing in saline environments. Thus, germination responses to salts has received considerable attention. The influences of salts on plant growth including germination include osmotic effects, ion effects and nutrient deficit. Therefore, germination strategy under salt stress should be considered based on these aspects of saline effects. We designed a series of experiments using grassland species and crops to study the related questions. We found that the osmotic effect was not the predominant effect under NaCl stress because the hydrotime model cannot predict germination of barley and grass species well. Then we proposed a salinity model which can better fit germination of these species under NaCl stress. The ion effect was adverse to germination only at high salinity, with sodium as an osmotic regulator to promote germination percentage and speed of barley at low and intermediate salinity. An experiment testing germination tolerance of 12 halophytes to salt type NaCl, Na2SO4and NaHCO3showed species-specific responses to different salts and they were either salt tolerators (high germination at high salinity) or avoiders (high recovery germination when salinity alleviated). Bigger seeds had higher salt tolerant capability at high salinity. Further analysis with mixed salts revealed that the most closely related salt parameters with germination and seedling growth was Na+concentration, not pH. Diluted salt solutions should be considered to conduct recovery germination experiments, rather than distilled water based on our study. We found that proper N application may aid seedling establishment of grass species in saline soils, which denoted nutrient deficit effect of salts. These results help to understand plant adaptation in saline environments and provide important information for salt tolerant species/crops breeding.