Nicula, C., Marian, M., Mihaly-Cozmuta, L., Peter, A., Mihaly-Cozmuta, A. - Adaptive Mechanisms Of Phaseolus vulgaris And Zea mays Seeds Grown In Agrocenoses Prone To Pollution With Heavy Metals 152 ADAPTIVE MECHANISMS OF Phaseolus vulgaris AND Zea mays SEEDS GROWN IN AGROCENOSES PRONE TO POLLUTION WITH HEAVY METALS Camelia NICULA * , Monica MARIAN * , Leonard MIHALY-COZMUTA * , Anca PETER * , Anca MIHALY-COZMUTA * * North University of Baia Mare, Faculty of Sciences, Department of Chemistry-Biology, Baia Mare, Romania Corresponding author: Camelia Nicula, North University of Baia Mare, Faculty of Sciences, Department of Chemistry-Biology, 76 Victoriei., 430122 Baia-Mare, Romania, tel.: 0040262430122, fax: 0040262276153, e-mail: vargacamelia@yahoo.com Abstract. The key goal of our research is the identification and analysis of accumulations of metal ions (Pb 2+ , Zn 2+ , Cu 2+ , Fe 2+ ) during their imbibition in seeds of Phaseolus vulgaris and Zea mays. We take as samples seeds collected from one metalliferrous and respectively from one non-metalliferrous area in Maramures County (North-West of Romania). We will refer following to an area as being “metalliferrous” because of its known high degree of pollution with metallic components, and to the other area as “non-metalliferous” because of being generally known as very much less exposed to pollution in general. We will subsequently name as being “polluted” the seeds originated in the metalliferous area, and respectively as “unpolluted” the seeds originated in the other area. We have thoroughly investigated in quantitative terms the existence of accumulations of each of the metal ions mentioned above during imbibition at three different levels of concentration. The seeds grown in the non-metalliferous area generally display a higher degree of absorption for each of the metal ions than the seeds grown in the metalliferous area. On the other hand, we have concluded that the concentration of heavy metals does not impact significantly the absorption capacity of both the polluted and unpolluted Z. mays seeds. The P. vulgaris seeds behaved differently, namely the content of metal ions absorbed went proportionally up, as the concentration of the initial solution went higher. Keywords: Phaseolus vulgaris, Zea mays, heavy metal accumulation, imbibition, adaptative mechanisms INTRODUCTION Anthropogenic factors (industrial activity, mining, sewage disposal, traffic, etc.) are mainly responsible for the growing concentration of heavy metals in soil. Heavy metals inhibit directly (by altering the catalytic function of enzymes, by damaging cellular membranes, by inhibiting the growth of roots) and indirectly (by dampening photosynthesis and mineral nutrient uptake, by structural changes) all physiological processes in plants [10, 14]. Another indirect effect of the contamination of soil with heavy metals consists in the decline of the microbiological activity, activity particularly vibrant in the rhizosphere. Plants usually show the ability to accumulate large amounts of metals without visible changes in their appearance or yield [13]. In many species of plants the level of metal accumulation can exceed even several hundred times the maximum level accepted for human beings, without a perceived negative impact on their growth or yield [24]. Therefore, it seems that plants can endure a level of environmental pollution that might be even several times higher than the level observed nowadays [9, 16, 21]. Metals accumulate and remain in soil along time frames spanning even hundreds of years, but impact in various ways the plants grown on polluted sites [19]. Various species of plants growing in a metalliferous area are known for their capacity to adapt to a polluted environment, by inactivating ions of heavy metals [3, 4, 26]. This occurs by binding the metal ions in excess and/or by changing the chemical composition and physical organization of cellular membranes [17, 22]. Many research teams [1, 6] have investigated the influence of heavy metals on the metabolism of plants, but data remains scarce about the accumulation of heavy metals in the reproductive organs of plants [5, 20]. Stefanov et. al. [22], which studied the accumulation of lead, zinc and cadmium in the seeds of various plants, showed that plants accumulate selectively ions of heavy metals in their seeds. Peanut and corn seeds accumulate mainly lead, pea seeds accumulate mainly cadmium and wheat seeds accumulate mainly zinc. On the other hand, Lane and Martin [11] showed that the coats of Raphanus sativus seeds were a strong barrier to lead and helped prevent the contamination of embryos until the coats were torn apart by the germinating embryonic root. There are reports on the inhibitory effect of lead on the germination of seeds of the Lupinus luteus [25], Oryza sativa [15] and Sinapis alba [7] species. One of the methods to assess how tolerant the seeds of a plant are to the ions of a metal consists in sowing those seeds in soil containing such ions. This substantiates that heavy metals have a significant effect on germination [2]. The studies mentioned above, unlike those by Lane and Martin [11], point to the significant influence of lead on the germination of seeds. In this situation it seems that lead ions impact the germination process depending on differences in the structure of seeds, more precisely depending on differences in the structure of coats. The role of the coat is to protect the embryo from harmful external factors is well known. But seed coats have a wide range of anatomic forms that do not exist in other organ or tissue of the plant [8]. Wierzbicka et. al [24] showed that out of all the families of plants tested, the Fabaceae are very sensitive as the concentration of metal ions goes up. The key goal of our research was to establish how the accumulation of heavy metals occurs during imbibition, the first step of the germination process, in seeds originating from a metalliferous area as compared to seeds from a non-metalliferous area. Our other ongoing concern is to collect evidence about how the adaptive behavior of seeds during imbibition has influenced the growth of the plant, as well as the