Salinity and Heavy Metals: Working Together for Tolerance in Sesuvium portulacastrum (L.) L.

The aim of the present review is to analyze different aspects of heavy metal tolerance and metal accumulation capacity of a perennial halophytic species Sesuvium portulacastrum. After a brief introduction to the species and description of possible characteristics related to adaptation to heterogeneous environments, detailed analysis of phenomenon of metal tolerance and metal accumulation is provided. In particular, it is described how different environmental factors, especially salinity, affect tolerance to heavy metals in S. portulacastrum and what morphological, biochemical, and physiological indicators can be used in this respect. Salinity is a crucial factor for increasing Cd tolerance in this species. Further, biochemical and molecular aspects of metal tolerance are briefly analyzed. Metal accumulation capacity of the species is analyzed and compared according to different experimental systems (tissue culture, hydroponics, soil) used as well as with results from taxonomically related halophyte species. A typical gradient of Cd accumulation potential was evident in S. portulacastrum plants in hydroponics, decreasing from roots (1600–2300 mg kg[[sup]]−1[[/sup]]) to stems (240–400 mg kg[[sup]]−1[[/sup]]) and leaves (110–130 mg kg[[sup]]−1[[/sup]]). A maximum potential for accumulation of Ni in S. portulacastrum was up to 1100 mg kg[[sup]]−1[[/sup]] in shoots and 2100 mg kg[[sup]]−1[[/sup]] in roots. Finally, aspects of practical application of S. portulacastrum in phytoremediation and other environmental technologies are discussed. It is necessary to test the ability of S. portulacastrum to accumulate different metals and their combinations in different soils, also in the presence of salt, paying special attention to the effect of mineral supply. The role of plant growth-promoting soil microorganisms and bacterial endophytes needs to be tested in this context.