Salt glands of recretohalophyte under salinity: Their evolution and adaptation.

Here, we studied the evolution of salt glands in 11 species of and determined their role in adaptation to saline environments by measuring the effect of NaCl on plant growth and salt gland characteristics. Cluster analysis divided species into three types (types I-III) according to salt-gland characteristics. A phylogenetic tree based on ITS sequences indicated an evolutionary relationship consistent with the geographical distribution of . We measured growth under different NaCl conditions (0, 100, 200, and 300 mM) for 40 days in three species (. , .  and . ) representing the three types. With increasing NaCl concentration, the biomass of all species was significantly reduced, especially that of . . Salt secretion ability and salt-gland density showed similar trends in three types. The order of salt tolerance was type I > type II > type III. We conclude that during adaptation to salinity, salt-gland evolution followed two directions: one increasing salt-gland density, and the other increasing salt secretion rate per salt-gland. This study provides a basis for potential mechanisms of recretohalophyte adaptation to salinity.