Translocation signatures of major elements in halophytes from hypersaline environments: the case study from Sečovlje Salina (Republic of Slovenia)

Abstract

Purpose Hypersaline environments are extremely vulnerable and important ecological niches. Because much knowledge has focused on the distribution of heavy metals in these areas, the detailed behavior of key major elements in hypersaline environments has not been elucidated in detail. This research aims to define the distribution, translocation pathways, and mobility patterns of the major elements in hypersaline sediments and halophytes. Materials and methods Samples of Sarcocornia fruticosa plants were collected from evaporation (ES) and crystallization (CA) sites in the Sečovlje Salina area (Republic of Slovenia). The major element contents were measured by digestion in HNO3 then aqua regia and analyzed by ICP-MS for ultra-low detection limits. Rhizo-sediments from EA and CA were processed using sequential extraction analysis to determine the precise fractionation of Al, Ca, Fe, K, Mg, Mn, and Na. To determine the translocation patterns of individual major elements in S. fruticosa, two indices were calculated: bioconcentration (BCF) and translocation factor (TF). Differences and similarities between samples and elements were highlighted using Statistica VII and Grapher 8 statistical software and Ward’s method, respectively. Results and discussion The obtained results confirmed that halophyte plants take up large amounts of the essential micronutrient Na due to high salinity, and that macronutrients (Ca, Mg, P, and S) are intensively translocated from the roots to the upper parts of the plant. The overall trend in translocation signature for major elements, distinguished by BCF and TF factor calculations, emphasizes that root tissues accumulate a significant amount of major elements and that accumulation depends on individual major elements. It also showed that the major elements Ca, Mg, Na, P, and S are highly translocated within plants, while the mobility of Al, Fe, and K is limited. Conclusions Our results suggest that the major elements are vital macronutrients for halophytes, but their accumulation in the roots and further translocation within the plant depend on individual elements and their dynamics. The translocation pattern of the major elements can be justified as follows: Ca is an essential element for plant growth, maintenance, and membrane integrity; Mg is a specific component of chlorophyll; Na is present because of the hypersaline environment; P is a key component of plant metabolic processes; S represents an important component of enzymes and other key proteins; Al and Fe are preferentially accumulated in roots; and plant leaves are generally undersupplied with K. The presented results are of great importance for the general knowledge and use/application of halophytes in agriculture and biotechnology.