Physiological and molecular responses of Betula platyphylla Suk to salt stress

Key message Our study found that birch employs different physiological pathways to tolerance salt stress in roots and leaves, and the genes closely correlated with these physiological changes were identified. Birches are fast-growing woody plants that are adapted to adverse environments, and are widely distributed from north Europe to northeast Asia. However, the salt stress tolerance mechanism of birch has little been studied. Here, we investigated the physiological and molecular response of white birch ( Betula Platyphylla ) to salt stress. Long-term salt stress inhibited photosynthetic activity, and decreased stomatal conductance of birch. Abscisic acid was induced in birch during the early salt stress period, and Ca 2+ level was increased slowly but maintained at a higher level for a long time. Under salt conditions, the salt-overly-sensitive pathway was activated in birch roots; reactive oxygen species (ROS) was highly accumulated, and superoxide dismutase is the main ROS scavenger in roots, while peroxidase is the main ROS scavenger in leaves. Proline plays a role in salt tolerance in both roots and leaves; however, soluble sugars and trehalose also have roles in salt stress tolerance, but mainly in leaves. Additionally, the genes that might have essential roles in controlling some of these physiological changes were identified, which represent good candidate genes to characterize the salt tolerance mechanism of birch. This study increased our understanding of the salt tolerance mechanism of birch plants.