Reproduction strategies of the silver birch (Betula pendula Roth) at post-industrial sites

Accumulation ability of trace metals by silver birch leaves in areas contaminated by Zn-Pb ore processing: Effects of excessive trace metal accumulation on specialized metabolism

The study was carried out in the most industrialised region of southern Poland. Four areas were selected for the study: the vicinity of the Miasteczko Śląskie Zn-Pb-works (ZW; with three transects selected: A, B, and C), and the metalliferous waste heaps (H1, H2, H3). Samples were taken from the surface soil layer, while only mature silver birch (Betula pendula Roth) trees (3-4 m high) growing spontaneously in the study area were selected for the collection of leaves. The analysis of metals including trace metals (TMs; Ag, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Tl, and Zn) in the soil and leaves, as well as the contents of specialized leaf compounds belonging to polyphenols were performed. In general, the B. pendula trees in transects A and B located within 500 m of the furnaces exhibited 3-9 times higher content of TMs in their leaves compared to the plants located further away from the Zn smelter. In contrast, the quantity of TM in trees from transect C was independent of distance. The accumulation of TMs in the leaves was significantly lower in the metalliferous waste heap sites compared to the ZW area. It was hypothesised that the accumulation of TMs in B. pendula leaves would depend on the location and distance from the polluting source. It was demonstrated that TMs content in soil affects the accumulation of phenolic acids and flavonoids.

Antioxidant activities in relation to the transport of heavy metals from the soil to different parts of Betula pendula (Roth.)

BACKGROUND

Birch is a tree with a common occurrence in the environment and its organs are used in the form of herbal material. An important aspect of this study is birch pollen, which is a problem for allergy sufferers, and due to a variety of environmental conditions, its allergenicity may increase. Among the organs studied, inflorescences deserve attention, which, as seen from an overview of the literature, are analysed for the content of heavy metals for the first time in this study.

RESULTS

This paper investigated the relationship between antioxidant properties and the content of heavy metals (Cu, Zn, Cd, Pb, Ni and Cr) as the plant's response to stress, taking into account both the vegetative and generative organs of the tree Betula pendula. While studying the accumulation of elements in individual organs, the research was extended to include the aspect of different environmental conditions, reflected in two soil types of differing physicochemical properties: sandy and silty soils. In order to thoroughly analyse the transport of the studied heavy metals from the soil to individual organs (leaves, inflorescences and pollen), ecotoxicological indicators were used. A modified translocation factor (TF) index into sTF (sap translocation factor) was presented as a novelty in research, calculated based on the content of selected heavy metals in the sap flowing to individual birch organs. This allowed for a more complete description of the transport of elements in the aerial parts of plants, indicating the accumulation of zinc and cadmium, especially in leaves. Among the studied environmental conditions which may affect the accumulation of heavy metals, sandy soil is of particular significance, conditioning lower pH values, among other things. However, analysis of the reaction of birch to the conditions of the soil environment and the content of heavy metals, based on antioxidant properties, demonstrated an evident reaction to stress, but without an unambiguous response among the studied vegetative and generative organs.

CONCLUSIONS

As birch is a plant with wide utility values, monitoring studies are advisable to exclude the risk of accumulation of heavy metals in its organs, and for this purpose it may be useful to use the sTF indicator and assess the antioxidant potential.

Effect of Drought and Heavy Metal Contamination on Growth and Photosynthesis of Silver Birch Trees Growing on Post-Industrial Heaps

Silver birch trees (Betula pendula Roth) are a pioneering species in post-industrial habitats, and have been associated with an expansive breeding strategy and low habitat requirements. We conducted ecophysiological and dendroclimatological studies to check whether there are any features of which the modification enables birch trees to colonise extreme habitats successfully. We characterised the efficiency of the photosynthetic apparatus, the gas exchange, the content of pigments in leaves, and the growth (leaf thickness and tree-ring width) of birch trees on a post-coal mine heap, a post-smelter heap, and a reference site. Birch growth was limited mainly by temperature and water availability during summer, and the leaves of the birch growing on post-industrial heaps were significantly thicker than the reference leaves. Moreover, birch trees growing on heaps were characterised by a significantly higher content of flavonols and anthocyanins in leaves and higher non-photochemical quenching. In addition, birches growing on the post-coal mine heap accumulated a concentration of Mn in their leaves, which is highly toxic for most plant species. Increasing the thickness of leaves, and the content of flavonols and anthocyanins, as well as efficient non-photochemical quenching seem to be important features that improve the colonization of extreme habitats by birches.