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Rahela is noticeably different, more flat, then curves of the other ones. Cultivars are marked as follow: diamonds — Ae. Normalization procedure at points O and J, and differentiation of results from polluted and reference soils, visualized the K-band, the most expressed with minus sign, for cv. Wiwena and the weakest for cultivars: Brudzynska with the negative sign and Rahela with positive one Fig.
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Normalization at points O and K visualized L-band Fig. All curves, but not that drawn for cv. Rahela, turned out to be almost identical, with the minus sign. The plot for the cv. Rahela was close to zero. The detected differences in soil composition of contaminated and reference site resulted from outdoor natural environments of rural areas, where the experiments were run. The fact that the vegetation seasons prior to Chl a fluorescence measurements were rainy and water availability did not limited the plant growth, opened the opportunity to interpret the differences in grasses performance as the response to HM.
More sand in soil at reference site might negatively affect the plant growth and performance but mostly during the low precipitation periods. Lower EC and pH at reference site could be the indirect effect of lower level of HM concentration, so it was assumed, that detected differences in plant performance resulted mostly from high HM level in soil.
The HM ion concentration in polluted site exceeded four fold the limits of Cd and Pb ions concentration for arable soils and six fold the limits of Zn, which are: Plants can tolerate relatively large amount of zinc in the soil, because it is an essential micronutrient, which deficiency as well as excess is harmful . Contamination of agricultural land by trace metals is the side effect of industrialization. In regions of long history of industrial emission elevated levels of cadmium, lead, zinc and other ions emitted in the course of coal and ore mining and processing are detected.
Since the maintenance of agricultural areas in those regions is important from ecological and sociological standpoint, the alternative farming activities are needed. Perennial grass biomass production for energy purposes is one of such solution  , .
However, caution should be made on practical use of biomass with high amounts of heavy metals. Considering its chemical composition it is not a substrate for direct energy production but a hazardous waste. Contaminated crop disposal process must be always planned in any phytoremediation activities, especially when large quantities of biomass are to be generated .
Many plant species has been already screened for their ability to accumulate HM. The latter seems much promising, because there are numbers of species available from many families, from which willows and perennial grasses are the most interesting .
Although the willow produces the high biomass with the effective nutrient uptake as well as the clone specific capacity for HM uptake, high demand for water and the specific harvest equipment required limit its usefulness to the large and flat fields rich in water, what is not frequent in the case of polluted areas .
Considering perennial grasses, there are no such limitations. A number of perennial grasses are used increasingly in Europe and North America as renewable bioenergy sources, as they can be grown with low maintenance on marginal soils and harvested to produce large volumes of biomass . Dynamics of HM ions absorption, transport and neutralization influence theirs toxicity. It was shown, that dose dependent relative cadmium toxicity is 4-fold higher than zinc and 3-fold higher than lead, for the onion epidermal cells used as a model. The way of HM inactivation affects theirs toxicity: HM ions can be stored in vacuoles, Cd ions can form the complexes with the cell wall polymers, Pb can be locked in endoplasmic reticulum vesicles .
Non neutralized HM ions induce formation of an excess of free radicals and slowdown turnover of chloroplasts proteins, mostly D1 protein  , . Thus the HM impact on the plant interferes with photosynthesis and the measurement of Chl a fluorescence reveals the disturbances. Minimal fluorescence reflects the oxidized state of quinone Q A , whereas the maximal one — the completely reduced state of the whole plastoquinone pool PQ .
ETC damage and sink dependent slowdown of electron flow are visible directly on fluorescence curves drawn on logarithmic time abscissa or on double normalized curves as well as can be recognized by parameters calculated using JIP-test and its applications . Fluorescence values F 2 , F 3 , F 4 and F 5 at times: 0. Usually under the stress conditions the fluorescence transient curve becomes flatter, i.
Our data distinguished cv. Rahela as the cultivar which reached the highest HM ions concentration in aerial parts and its photosynthesis was the most influenced by them. It indicated a decline of the maximum efficiency at which light absorbed by plants grown on the polluted soil is used for the reduction of Q A  , . Kalaji et al. The other statistical method, presented by Goltsev et al.
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We have found the PCA analysis as a convenient tool in plant grouping. Since the first PCA variable was dependent on measured parameters Fig. Analysis of normalized curves distinguish cv. It can be hypothesized that in such a situation the ascorbate can be the electron donor in chloroplasts of plants from the polluted area  ,  ,  , . Again the cv. Rahela stood out, as on the Fig.
A negative L-band indicates higher grouping of PSII antennas as compared to reference sample  ,  ,  , which is the fact for all cultivars, beside cv. The similarities of the shape of all normalized curves for all cultivars beside cv. Rahela may suggest the different physiological response to stress of that one.
Heavy Metal Stress in Plants: From Biomolecules to Ecosystems - Google Libros
The y-axis shift is detected on all graphs. Rahela is at the top. Obtained results can be interpreted as a mark of cultivars reaction on HM ion stress. It looks that all cultivars except cv. Those cultivars, under the influence of HM ions stress accelerated metabolism, which is a typical physiological response of plants slightly resistant or non-resistant to the stress. Resistant plants typically launch additional defense mechanisms and rebuild its metabolism  , .
Contrary to expectation, cv. Rahela which sequestrated the highest concentration of HM ions in the aerial part, did not show PSII antennas grouping under the stress, as other cultivars did. It should be considered that such cultivars which survive the stress by accelerating photosynthesis as well as the whole metabolism could be less resistant in front of additional environmental stresses such as i. Festuca arundinacea cv. Rahela in fact deals the best with the HM stress.
Its antennas are not damaged, might be due to redox guard in the form of ascorbate which in other cultivars were not induced strongly enough to be visible on double normalized graphs. Analyzed the data: GZ KR. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Abstract Chlorophyll a fluorescence gives information about the plant physiological status due to its coupling to the photosynthetic electron transfer chain and to the further biochemical processes. Introduction Phytoremediation requires plants that maintain good fitness on contaminated soils in parallel with the highest possible concentration of pollutants in aerial parts .
Materials and Methods Field Experiment The experiment was located on contaminated soil on Silesia, southern Poland Plant Materials Five perennial grass cultivars: tall oat grass, Arrhentherum elatius L. Soil Analysis Five representative soil samples were collected from 0—30 cm horizon at each site for chemical analysis. Determination of HM Ions Concentration in Plant Biomass Plant material was washed with tap water and then with deionised water in an ultrasonic washer to remove all soil particles followed by drying at 70 o C for 3 days.
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Table 1. Monthly precipitation and mean temperatures during the course of experiment in polluted and reference site. Results In order to examine, to what extent the Chl a fluorescence was useful in studies of the effect of HM polluted soil in natural agro-ecosystem, localizations with the most similar soil composition beside HM ions concentration were chosen to run the experiment.