Comparative study on the resistance of Suaeda glauca and Suaeda salsa to drought, salt, and alkali stresses

Suaeda glauca and Suaeda salsa are annual chenopod herbs that grow well in saline-alkali lands, and they share a number of morphological and physiological traits. We found that the natural distributions of these two halophytes were regionally heterogeneous in the saltmarsh of the Bohai coast, China. In the present study, habitat surveys and laboratory tests were conducted to examine the adaptability of S. glauca and S. salsa in variable environments. The habitat survey showed that S. glauca preferred to establish in soil with a lower moisture, lower EC, and higher pH as compared to S. salsa, suggesting that the adaptability of S. glauca and S. salsa to drought, salt, and alkali conditions varies. In the laboratory, these abiotic stresses were simulated at varying degrees by hydroponic culture. Plant biomass, water content, cations and anions distribution were measured after 10 days treatments. The results showed that (1) the inhibitory effect of the drought treatment on S. salsa shoot fresh weight and water content was less than that on S. glauca. Low and moderate drought treatments inhibited the root growth of S. glauca but promoted S. salsa root growth with Mg2+ and SO42- accumulation. (2) S. glauca and S. salsa were both highly resistant to salinity, and their adaptive strategies were similar. The optimum NaCl concentration for S. salsa was 200 mM, higher than that of 100 mM for S. glauca, and a greater K+ deficiency was observed in S. glauca roots under high salinity treatment. (3) Although high alkali stress was destructive to S. glauca and S. salsa, low alkali treatment promoted the plants root growth, and this promotion in S. glauca was greater than that in S. salsa. Furthermore, low and moderate alkali treatments significantly increased Ca2+ and Mg2+ contents in S. glauca root but had little effect in S. salsa. These results indicated that S. salsa was more tolerant to drought and salt stresses than S. glauca but less tolerant to alkalinity. The resistance variation between the two species was mainly due to their root adaptability and the potential cations regulation. Moreover, our study suggests that S. salsa is an optimal species for the artificial revegetation in high saline land, while S. glauca is more adaptable to alkali land.