Responses of the carbon and oxygen isotope compositions of desert plants to spatial variation in soil salinity in Central Asia

We examined the isotopic parameters in two C₃ species (Artemisia diffusa H. Krasch and Tamarix hispida Willd.) and a C₄ species [Haloxylon aphyllum (Minkw.) Iljin.] growing or planted in soils with different levels of salinity in a Central Asian desert. The oxygen isotope ratios of stem water (δ¹⁸O_stem) in T. hispida and H. aphyllum distributed in high-salinity zones were similar to the δ¹⁸O of artesian water (δ¹⁸O_artesian) and different from that in A. diffusa distributed in lower-salinity zones. This indicates that T. hispida and H. aphyllum depend on water with low salinity in the deeper soil layer, whereas A. diffusa depends on water in the shallower soil layer that would be affected by salt accumulation. The carbon isotope composition of leaf organic matter (δ¹³C_om) and oxygen isotope enrichment in leaf organic matter above stem water (Δ¹⁸O_om) were lower in A. diffusa than in the other species. The responses of δ¹³C_om and Δ¹⁸O_om to soil salinity observed for T. hispida suggest that the species decreased its transpiration rate and increased its intrinsic water-use efficiency in response to increasing soil salinity. The δ¹³C_om and Δ¹⁸O_om of H. aphyllum were higher than those of the C₃ species, and were not correlated with soil salinity, suggesting that H. aphyllum reduced its salt uptake by decreasing transpiration—even though it was able to access less saline water in the deeper soil layer. These results indicate that the water-use strategy of desert plants in high-salinity environments can be assessed based on their carbon and oxygen isotope ratios.     

Genetic Markers and Psoriasis in Three Ethnic Populations of Dagestan

Analysis of clinical material obtained from the individuals (49 psoriasis patients and 357 individuals without this disease) representing three ethnic populations of Dagestan (Avars, Dargins, and Kumyks) was performed. Polymorphism of the blood group loci AB0, Rhesus (RH), Kell, P, and Lewis, as well as of the protein-encoding loci for haptoglobin (HP), transferrin (TF), the third complement component (C′3), group-specific component (GC), and the enzymes, including glycosylase (GLO1), esterase D (ESD), 6-phosphate dehydrogenase (6PDG), and acid phosphatase (ACP), was studied. It was demonstrated that in the pooled sample of Avars and Kumyks the Lewis system phenotype Le(a-b-) and the phenotype ee of the Rhesus system were statistically significantly more frequent among the psoriasis patients (P = 0.0488 and P = 0.0166, respectively), than among healthy controls of the same ethnic groups. It was suggested that for the pooled sample of Avars and Kumyks, homozygosity for the recessive ee (RH) in combination with the Le(a-b-) phenotype, representing homozygosity for recessive allele le, was the risk factor for the development of psoriasis.