Physiological Adaptation of Three Wild Halophytic Suaeda Species: Salt Tolerance Strategies and Metal Accumulation Capacity

Abstract

Understanding salt tolerance mechanisms in halophytes is critical for improving the world’s agriculture under climate change scenarios. Herein, the physiological and metabolic responses of Suaeda monoica, Suaeda vermiculata, and Suaeda schimperi against abiotic stress in their natural saline environment on the east coast of the Red Sea were investigated. The tested species are exposed to different levels of salinity along with elemental disorders, including deficiency in essential nutrients (N&P in particular) and/or elevated levels of potentially toxic elements. The tested species employed common and species-specific tolerance mechanisms that are driven by the level of salinity and the genetic constitution of Suaeda species. These mechanisms include: (i) utilization of inorganic elements as cheap osmotica (Na+ in particular), (ii) lowering C/N ratio (S. monoica and S. schimperi) that benefits growth priority, (iii) efficient utilization of low soil N (S. vermiculata) that ensures survival priority, (v) biosynthesis of betacyanin (S. schimperi and S. vermiculata) and (vi) downregulation of overall metabolism (S. vermiculata) to avoid oxidative stress. Based on their cellular metal accumulation, S. monoica is an efficient phytoextractor of Cr, Co, Cu, Ni, and Zn, whereas S. vermiculata is a hyper-accumulator of Hg and Pb. S. schimperi is an effective phytoextractor of Fe, Hg, and Cr. These results highlight the significance of Suaeda species as a promising model halophyte and as phytoremediators of their hostile environments.

Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change

“…The article by Ibraheem et al [ 22 ] refers to another genus of the Amaranthaceae family. The authors compared the physiological and metabolic stress responses of three Suaeda species ( S. monoica , S. vermiculata , and S. schimperi ) in their natural saline environments—contrary to the other papers in this Special Issue, which report studies under controlled greenhouse conditions.…”

Research Advances on Molecular Mechanism of Salt Tolerance in Suaeda

“…Ex J.F.Gmel. were different [ 90 ]. The chlorophyll content in S. salsa was improved after NaCl stress [ 90 ].…”

“…The chlorophyll content in S. salsa was improved after NaCl stress [ 90 ]. When cultured with 200 mM NaCl for 14 days, the photosynthetic capacity including net photosynthetic rate (Pn), electron transfer rate, NADPH level, activities of ferredoxin-NADP oxidoreductase, ribulose-1, 5-bisphosphate carboxylase (Rubisco), and Rubisco activase were improved significantly in S. salsa , and 500 mM NaCl had no adverse effect on those parameters [ 31 , 90 ]. Low salt stress had little effect on the photosynthesis of S. corniculata seedlings, while high salinity inhibited their photosynthesis [ 91 ].…”

“…salsa shows a high resistance to low salinity [ 92 ], making plant growth more adaptable under low salinity conditions (8 ppt). Therefore, increased photosynthetic activity may play a critical role in the biomass enhancement of Suaeda under saline conditions [ 90 ].…”

“…The Suaeda species exhibited significant variation in amino acid biosynthesis under similar salinity conditions. For example, S. monoica and S. schimperi accumulated significantly higher foliar proline than S. vermiculata , suggesting that proline is an important compatible osmolyte in S. monoica and S. schimperi species [ 90 ].…”