**3. Results**

#### *3.1. Soil Characteristics*

The soils in *B. prostrata* habitats (populations) differed significantly in the degree and vertical changes in salinity chemistry. In each of the seven habitats, the soil salinity the 0–20 cm, 20–40 cm, and 40–60 cm in layers was studied. Two habitats (Nos. 1 and 2) had non-saline or slightly saline soils (Table 1). The soils in the other five habitats (Nos. 3–7) were much more saline: the upper 0–20 cm layers were non-saline or slightly saline (Ssalts = 0.11–0.25%); the 20–40 cm layers were moderately or highly saline (Ssalts = 0.5–1.17%); and the 40–60 cm layers were highly or extremely saline (Ssalts = 1.35–2.57%) (Table 1). In all habitats, except for No. 4, Na<sup>+</sup> was the dominant cation: 0.03–2.27 cmol(eq)/kg, 0–20 cm layer; 0.32–8.95 cmol(eq)/kg, 20–40 cm layer; and 3.15–23.25 cmol(eq)/kg, 40–60 cm layer. The Ca2+ ion predominated in habitat No. 4. In other soils, Ca2+ and Mg2+ contents also significantly contributed to salinity at 0.28–12.9 and 0.26–8.32 cmol(eq)/kg, respectively. Chlorides and sulfates were the dominant anions (Table 1).

**Table 1.** Contents of anions and cations in soils of the seven *Bassia prostrata* habitats in the northwestern Caspian Lowland.


Ssalt—the sum of salts represents the sum of the mass fraction of ions from the solid soil residue (%). Values are means ± standard errors (*n* = 3).

#### *3.2. Plant Growth and Water Content*

*B. prostrata* plants varied significantly in growth parameters between populations (Figure 2). The greatest plant heights were in populations Nos. 2, 4, and 7 (Figure 2A), while the highest fresh (FW) and dry (DW) biomass aboveground parts of plants were observed in populations No. 4 and No. 6 (Figure 2B,C). At the same time, the water content (W) in the plants was the highest in population No. 7 (Figure 2D).

**Figure 2.** Growth parameters and water content of *Bassia prostrata* plants from seven populations. 1–7—populations; (**A**)—plant height; (**B**)—fresh biomass (FW) aboveground part of plants; (**C**) dry biomass (DW) aboveground part of plants; (**D**)—water content (W) of plants. Values are means ± standard errors (*n* = 5).

#### *3.3. Population Genetic Diversity*

An analysis of eight enzyme systems in seven *B. prostrata* populations revealed ten loci; one of them (*Sod*) was monomorphic in all populations. The other nine loci were polymorphic: *G6pd* in all populations; *Me* in six populations; *Gdh* in four populations; *Got, 6pgd*, and *Mdh-A* in 3 populations; and *Dia-A, Dia-B*, and *Mdh-B* in one population. Values of observed heterozygosity (*H*o) varied from 5 to 47% among polymorphic loci and populations (Figure 3A), whereas expected heterozygosity (*H*e) varied from 5% to 59% (Figure 3B). The average (for all loci) observed heterozygosity varied from 5.5% to 11.1%, and expected heterozygosity varied from 6.2% to 15.9% in populations of *B. prostrata* (Figure 3C). The polymorphic loci proportion (*P*) among the populations was 20–70% (Figure 3C). On average, populations Nos. 2, 3, 5, and 6 were more polymorphic than populations Nos. 1, 4, and 7 (Figure 3).
