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Allium cepa var. agrogarum L. seedlings grown in nutrient solution were subjected to increasing concentrations of Cd2+ (0, 1, 10, 100 μM). Variation in tolerance to cadmium toxicity was studied based on chromosome aberrations, nucleoli structure and reconstruction of root tip cells, Cd accumulation and mineral metabolism, lipid peroxidation, and changes in the antioxidative defense system (SOD, CAT, POD) in leaves and roots of the seedlings. Cd induced chromosome aberrations including C-mitoses, chromosome bridges, chromosome fragments and chromosome stickiness. Cd induced the production of some particles of argyrophilic proteins scattered in the nuclei and even extruded from the nucleoli into the cytoplasm after a high Cd concentration or prolonged Cd stress, and nucleolar reconstruction was inhibited. In Cd2+-treated Allium cepa var. agrogarum plants the metal was largely restricted to the roots; very little of it was transported to aerial parts. Adding Cd2+ to the nutrient solution affected mineral metabolism. For example, at 100 μM Cd it reduced the levels of Mn, Cu and Zn in roots, bulbs and leaves. Malondialdehyde content in roots and leaves increased with treatment time and increased concentration of Cd. Antioxidant enzymes appear to play a key role in resistance to Cd under stress conditions.
The aim of the experiment was to study the effects of selenium ions on the changes in membrane permeability for K and Ca in the leaves of rape during cadmium stress. The of stress level was determined by changes in the mass increment and lipid peroxidation (MDA concentration) in 3-week-old seedlings cultured in vitro on Murashige and Skoog [1962] medium (control) and on medium containing 600 µМ CdCl2. Selenium was added at the concentration of 2 µМ (Na2SeO4) to the control and medium containing cadmium ions. The level of K and Ca was determined with ionoselective electrodes after one hour of shaking leaf discs (membrane permeability) and heating to 100°C (total ion content). Cadmium present in the nutrient medium inhibited the mass increment and increased MDA concentration, and significantly decreased membrane permeability for K and Ca. In the mixtures of cadmium and selenium, selenium ions partially reduced the effects of the stress-inducing cadmium action on the studied physiological parameters and membrane permeability to the studied ions. The observed protective effect of selenium can be the result of the effect of this substance on both the activity of ion channels and peroxidation of membrane lipids.
Contamination of the environment with heavy metals such as Cd is a serious problem of modern world. Exposure of plants to Cd leads to oxidative stress, inhibition of respiration and photosynthesis, increased rate of mutation and, as a consequence, stunted growth and yield decrease. One of the common reactions of plants to cadmium stress is over-production of ethylene, however the exact role of this hormone in plants response to Cd is still unrecognized. The aim of the present study is evaluation of the impact of an ethylene synthesis inhibitor, Co, on the response of soybean seedlings to cadmium stress. The experiments included measurements of growth, cell viability, ethylene production and expression of genes associated with cellular signaling in soybean seedlings exposed to CdCl2 (with Cd in a concentration of 223 μM) and/or CoCl2 (with Co in concentration of 4.6 μM). Surprisingly, the results show that Co has no effect on ethylene biosynthesis, however, it affects cell viability and expression of Cd-induced genes associated with plant signaling pathways. The affected genes encode mitogen-activated protein kinase kinase2 (MAPKK2), nitrate reductase and DOF1 and bZIP2 transcription factors. The role of Co in plants response to cadmium stress and its potential use as an ethylene inhibitor is discussed.
Seedlings of wheat (Triticum aestivum L.) cultivars Jing 411, Jinmai 30 and Yangmai 10 were exposed to 0, 10, 20, 30, 40 or 50 μM of CdCl₂ in a solution culture experiment. The effects of cadmium (Cd) stress on wheat growth, leaf photon energy conversion, gas exchange, and Cd accumulation in wheat seedlings were investigated. Gas exchange was monitored at 3, 9, 24 days after treatment (DAT). Growth parameters, chlorophyll content, leaf chlorophyll fluorescence, and Cd concentration in shoot and root were measured at 24 DAT. Seedling growth, gas exchange, chlorophyll content, chlorophyll fluorescence parameters were generally depressed by Cd stress, especially under the high Cd concentrations. Cd concentration and accumulation in both shoots and roots increased with increasing external Cd concentrations. Relationships between corrected parameters of growth, photosynthesis and fluorescence and corrected Cd concentrations in shoots and roots could be explained by the regression model Y = K/(1 + exp(a + bX)). Jing 411 was found to be Cd tolerant considering parameters of chlorophyll content, photosynthesis and chlorophyll fluorescence in which less Cd translocation was from roots into shoots. The high Cd concentrations were in shoots and roots in Yangmai 10 which has been found to be a relative Cd tolerant cultivar in terms of most growth parameters.
Heavy metal toxicity has become a universal threat to all life forms, including plants. The main purpose of this study was to identify the gene expression profiling of MAPK, Thioredoxin, and MnSOD genes in wheat seedlings as affected by cadmium treatment. For this experiment, the quantitative Real-Time PCR on RNA isolated from shoots of wheat exposed to CdCl₂ at a concentration of 100 mg/L was used. Results showed that in wheat seedling that exposed to cadmium stress for six days of beginning constant cadmium stress, Thioredoxin gene expression showed a large rise compared with the control sample, MnSOD gene expression increased compared with non-treated wheat seedling at the same times, but unlike the Thioredoxin and MnSOD genes, MAPK gene expression has no significant changes. Of course, it is possible that other times of beginning treatments (instead of six days) cause a change in this gene expression.
Previously, a stable cell suspension of cucumber tolerant to 100 µM CdCl2 was obtained (Gzyl & Gwóźdź, 2005, Plant Cell Tissue Organ Cult 80: 59-67). In this study, the relationship between the activity of antioxidant enzymes and cadmium tolerance of cucumber cells was analyzed. A cadmium-sensitive and the cadmium-tolerant cell lines were exposed to 100 µM and 200 µM CdCl2 and the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX) and guaiacol peroxidase (POX) were determined. In the sensitive cell line, a decrease of total activity of SOD and POX was observed, whereas the activity of CAT and APOX significantly increased in metal-supplemented medium. By contrast, in the tolerant cells, the total activity of antioxidant enzymes decreased (SOD, CAT) or was maintained at approximately the same level (APOX, POX). Moreover, a different pattern of isoenzyme activity was observed in the tolerant and sensitive cells. These results suggest that an enhanced activity of antioxidant enzymes is not directly involved in the increased tolerance to cadmium of the selected cucumber cell line.
Badania przeprowadzono na korzeniach Lolium multiflorum L.. Rośliny pochodziły ze stacji badawczej w Dublanach, Uniwersytetu Rolniczego we Lwowie. Przed siewem nasion, do gleby (czarnoziem leśno-stepowy, wyługowany, wytworzony z lessu o pH = 6,8) dodano roztwór CdCl2w ilościach kadmu 0 (obiekt kontrolny), 3, 15, 30 mg·kg-1 gleby. Rośliny zebrano w fazie kwitnienia i w fazie pełnej dojrzałości nasion. Pozorną powierzchnię właściwą korzeni tych roślin wyznaczano z izoterm adsorpcji pary wodnej, których pomiar przeprowadzono zgodnie z Polską Normą PN-Z-19010- 1. Do opisu danych doświadczalnych adsorpcji-desorpcji pary wodnej zastosowano model równania BET. Korzenie roślin pochodzące z obiektów z Cd+2 charakteryzowały się mniejszą wielkością pozornej powierzchni właściwej niż korzenie z obiektów kontrolnych. Stwierdzono że, ilości kadmu 15 i 30 mg·kg-1 gleby wpłynęły istotnie na spadek wielkości pozornej powierzchni właściwej korzeni Lolium multiflorum L. w fazie kwitnienia. Dla korzeni zebranych w fazie pełnej dojrzałości nasion, istotny spadek tego parametru wykazano dla dawki kadmu 30 mg·kg-1 gleby. Kadm dodany do gleby w ilości 3 mg·kg-1 tylko nieznacznie wpłynął na wielkość pozornej powierzchni właściwej korzeni Lolium multiflorum L. Dawki kadmu dodane w ilości 30 mg·kg-1, spowodowały, że względne zmiany wielkości pozornej powierzchni właściwej korzeni starszych (faza pełnej dojrzałości nasion) były większe niż dla korzeni zebranych w fazie kwitnienia roślin. Intensywność zmian pozornej powierzchni właściwej korzeni zależała nie tylko od odporności roślin i stężenia czynnika stresowego, ale również od czasu ekspozycji rośliny na stres. Obserwowane zmiany pozornej powierzchni właściwej badanych korzeni, związane były prawdopodobnie ze zmianami w procesach fizjologicznych, które zachodziły w roślinie pod wpływem przedłużającego się stresu.
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