# Elemental Profiles of Wild _Thymus_ L. Plants Growing in Different Soil and Climate Conditions
## 3 Results and Discussion
Figure 1: Elemental profiles of the soils. Figure 2: The elemental profiles: (**a**) essential elements; (**b**) toxic and sub-toxic (or sub-essential) elements. The element content in plants usually reflects their biological necessity for plant survival. The element concentration is also an indication of the composition of the soil in which they grow. As was previously shown [26], higher Al content in the organs of _Thymus serpyllum_ L. may result from the increased abundance of this element in the soil. A similar phenomenon was also observed in plants growing in soils with a higher chromium content [25]. Chromium and nickel are usually considered toxic elements, but plants can use these metals in the biosynthesis of organic compounds for electron charge transfer, just as Cu, Fe, Mn, Co, Mo and V are used [1; 2; 40]. The behaviour of Ba and Sr in plant organs depends on their content in the soil. If the element is present in large quantities in the soil, then its concentration decreases towards the flowers. If the element is not present in large quantities, then its accumulation in flowers will remain constant. Thus, when the concentration of Ba in the soil is 400 and 93 mg/kg, concentrations of 126 and 113 mg/kg in flowers are observed; when the concentration of Sr in the soil is 100 and 150 mg/kg, concentrations of 126-113 mg/kg and 64-52 mg/kg are observed in flowers. The Ca/Sr ratio in plant organs is 70-138 for _Thymus serpyllum_ L. and 123-402 for _Thymus buikalensis Serg._ L., accordingly. The increase in the ratio of these elements indicates an increase in the contribution of enzymes to the transfer of elements from soil in the Baikal plant, situated in a wetter climate [41]. The increased content of Cr, Ni and V in _Thymus buikalensis [PERSON]_ [PERSON] flowers is likely associated with the same effect. However, it is difficult to unambiguously attribute biophilic behaviour to Ni, Co and Cr. Such elements as Be, Ga and Pb were evaluated as toxic, since even at low concentrations in soils, their abundances decreased sharply in the root system, although they accumulated in small quantities in the flowers. We observed an intense accumulation of phosphorus from the roots to the leaves and flowers even at low P levels in the soil. The food supply of biophilic K, Ca, Mg, Fe, Mn and Na from the soils to the plants was partially limited but reached the maximum concentration in the flowers. Similar elemental profiles of the \"roots-stems-leaves-flowers\" sequences for biophilic B, Cu, V and Zn for the different _Thymus_ species were obtained (Figure 2). It is known that silicon compounds are involved in the synthesis of proteins, which allows for the transport of soluble silicon compounds required for the mechanical strength of the cell wall. In gymnosperms and aquatic plants, the silicon content is often higher than 1 wt.%. The element is difficult to analyse by ICP-AES and ICP-MS. During polymerisation and hydrolysis of silicon, large particles are formed in the solutions of the plant samples, which are filtered out before the analysis or are distilled through heating with hydrofluoric acid [39]. These Si contents are not determined by method of X-ray fluorescence spectrometry because it has a high detection limit for silicon. The factors mentioned above usually cause the exclusion of silicon from the analyte list. For plants grown in the studied climatic conditions, the concentrations of Si and Ti in the \"roots-stems-leaves-flowers\" sequence are significantly different, though in flowers their abundances are similar: Si--3.70 wt.% and Ti--400 mg/kg (Table 1). These are probably the maximum concentrations of Si and Ti that _Thymus_ plants can accumulate and use in essential processes safely. In the shoots of _Thymus marshallianus_ L., the silicon content was found to be 2.21 wt.% [15], which is in good agreement with the data obtained for the studied plants, averaging for stems and leaves 2.91 and 1.19 wt.%, respectively. Data concerning the Ti content in _Thymus_ plants were not found in the literature.