EWA PRZEDPEŁSKA, SYLWIA TRĄBKA, KRZYSZTOF BRZOST (authors of photographs)
MAŁGORZATA WIERZBICKA (project manager)

University of Warsaw,
Faculty of Biology, Institute of Experimental Plant Biology, Department of Ecotoxicology;
Miecznikowa 1, 02-096 Warsaw
e-mail: wierzbicka@biol.uw.edu.pl

Description popularizing the research project

An edelweiss is covered with hairs, a stinging nettle and a sundew, too. The thicker or thinner fur on leaves and shoots is necessary and serves a number of life functions. Numerous species are equipped with unpleasant weapon which contains irritating substances, others have a hunting weapon, namely hairs covered with sticky droplets, others use their hairs as a protective layer against drought, heat, excessive vaporizing or cold. The adaptation processes which ultimately led to plants wholly or partially covered with delicate tomentose have been continued for millions of years. It took the plants merely a few hundred generations to find a new application to the hairs and turn some of them into accumulators of heavy metals.
As we all know, heavy metals are toxic. Cadmium or zinc in excess disturb life processes of plants at all organizational stages: from genes level to leaves, flowers and fruit. The species have little chance to leave the unpleasant place or avoid contact with the toxins. The sometimes highly-reactive heavy metals, which penetrate the interior of the plant, must be separated from metabolism, otherwise they may interact with the key particles of nucleotide acid and enzymatic proteins. For many species the hairs on the leaves became the reservoir of cadmium and zinc. When there are not enough of them new ones grow and the silver fur gets thicker.
That happens in Silesia. The waste heaps are covered with surprisingly rich green. Some of the plants have thicker fur than their cousins from e.g. Mazury. From the evolutionary perspective the period of industrial activity of man is just a twinkling of an eye. Nevertheless the plants used the period well and adapted their mechanisms to neutralizing the metals. With a bare eye we can observe how the hairs grow thick. Using a good microscope we can see the metals stored within.
Biscutella laevigata and Cardaminopsis have fur. The typical inhabitants of waste heaps in an impressive way join style and struggle for survival.

Abstract

Upper Silesia is, without a doubt, a perfect testing ground for biologists as here both intensive mining and well developed industry had created a unique field laboratory. In this region vast areas of land are covered with heaps of waste rock material as well as industrial and smelting wastes. This inhospitable land is characterised by lack of well developed soil, very low humidity or even drought, high insolation, low nutrients concentration and high amounts of heavy metals. In spite of such harsh conditions waste heaps are colonised by vegetation.
Our research, which has been conducted here for many years, aims to get insight and gain better understanding of mechanisms that allow plants to live in environment polluted with heavy metals. The present study focus on a problem of heavy metals uptake, translocation and accumulation. It is a part of research project on morphological, physiological and genetic adaptations that had evolved in plants and allowed them to live in the hard waste heap conditions. All research are carried on 6 common plant species from a waste heap. A light microscopy (passing light, phase-contrast and dark field) is here the main research method.
Our investigation has showed that some heavy metals (such as zinc and cadmium) are transported to the plant's above-ground parts and accumulated in trichoms that cover the surface of each leaf. Extremely high amounts of noxious metals can be accumulated in that way as the size of a trichom cell is often much bigger than average size of other leaf cells. Thanks to this storage of heavy metals there is not any harm to plant metabolism. For that reason plants from waste heaps are more densely covered with trichoms than plants from non-polluted areas. This phenomenon is a good example of plant adaptation to difficult environmental conditions of waste heap.