Calcium modifies Cd effect on runner bean plants

https://doi.org/10.1016/S0098-8472(98)00045-8Get rights and content

Abstract

The effect of different Ca concentrations in the growth medium on the toxicity of 25 μM CdSO4 was studied in runner bean plants (var. Piękny Jaś) at two different growth stages of primary leaves. In young plants growing in a medium with low level of Ca a treatment with Cd for 12 days resulted in Ca accumulation in roots, a strong reduction of the leaf area, a decreased monogalactosyl diacylglycerol/digalactosyl diacylglycerol ratio and efficiency of the photosynthetic apparatus. In leaves of older plants growing under the same conditions, and surviving Cd treatment, a high accumulation of Ca but a low one of Cd, chlorosis of leaves, a decrease of the ratio monogalactosyl diacylglycerol/digalactosyl diacylglycerol and photosynthetic activity were shown. At a high level of Ca in the nutrient medium plant roots showed a remarkably high specificity to accumulate Cd but the toxic effect of the metal on plant growth parameters and content of pigments was decreased. No changes were observed in the level of galactolipids, but changes in fluorescence quenching were recorded. Calcium deficit enhanced the effect of Cd toxicity, including primary photochemistry, whereas excess Ca reduced toxic effects, while it is increasing the nonphotochemical quenching of excitation energy.

Introduction

Calcium is a well-known component of signal transduction pathways. It can activate and regulate many processes in eukaryotic cells. Small intracellular changes of Ca concentration can regulate such processes as elongation and division of cells (Hepler and Wayne, 1985), the metabolism (Kauss, 1987, Bush, 1995), transport and secretion (Bush, 1995, Marschner, 1995). Although Ca can constitute more than 10% of dry weight of mature leaves, without showing distinct symptoms of toxicity or inhibition of plant growth (Marschner, 1995), only its small part defined as ‘free cytosolic calcium’ participates in regulation of metabolism, growth and development of plants. Calcium is taken up by plants passively and only by root tips (Shuman, 1994). However, in general, the mechanisms of trans-plasmamembrane metal transport in higher plants are poorly understood (Ernst et al., 1992). Moreover, transport of Ca can be competitively impeded by other elements, especially by univalent cations. Attention is also given to the fact that this element can be displaced by other ions, for example, by Cd ions, which are toxic to plants. Cadmium is taken up by plants, using the paths of Ca transport. It is therefore reasonable to suppose that the presence of Cd in the medium can change Ca level in plant cells and thereby influence the processes of plant growth and metabolism. Attention was drawn earlier by Greger and Lindberg (1987)to the fact that effects of toxic Cd action, found in sugar beet roots, resemble symptoms of Ca deficit. Although toxic effects of Cd on plants are well documented (Barceló and Poschenrieder, 1990, Krupa and Baszyński, 1995, Prasad, 1996) the mechanism of its cellular action is still unclear.

From our earlier studies it is known that the stage of plant growth differs in the sensitivity during Cd treatment and Cd exposure time (Skórzyńska-Polit and Baszyński, 1995, Skórzyńska-Polit and Baszyński, 1997). We observed disturbances mainly in growth processes of young bean plants and changes in the activity and efficiency of the photosynthetic apparatus in older plants (Skórzyńska-Polit and Baszyński, 1997). Taking into account these results and the significance of Ca to plants we considered that disturbances in calcium management influenced by Cd are possible. Searching for elucidation of the mechanism of Cd action on bean plants at their different growth stages we hypothesized that a lower or higher amount of Ca than normal, present in the Knop solution can either enhance the toxic effect of Cd on plants or diminish it.

Changes in plant metabolism resulting from disturbances in supply of mineral elements may induce generation of reactive oxygen species. Excess of free radicals in plant cells leads to oxidative stress. Its effects can be reduced through the mediation of enzymatic and nonenzymatic antioxidants (Scandalios, 1990, Foyer et al., 1994), among which is GSH or hGSH. According to this assumption, in plant cells there is a significant increase in the level of thiol compounds under stress conditions and their utilization for diminishing the negative effects of stress (Walker and McKersie, 1993). We hypothesized that different concentrations of Ca in the medium are responsible for changes of hGSH level as an antioxidant factor in plant cells and utilization of this tripeptide in the synthesis of Cd-binding hPCs.

Section snippets

Plant material

Runner bean plants (Phaseolus coccineus L., cv. Piękny Jaś) were germinated from seeds on wet filter paper in a thermostated darkened chamber (23°C, 95% relative humidity). From day 5 the seedlings were cultivated hydroponically (five plants per pot, three pots per treatment) in aerated modified Knop nutrient solution. The nutrient solution was composed of (mg l−1): Ca(NO3)2·4H2O-1000; KH2PO4-280; MgSO4·7H2O-250; KCl-120; H3BO3-0.2; MnSO4-0.5; CuSO4-0.05; ZnSO4-0.1; (NH4)6Mo7O24·4H2O-0.025.

Responses of young plants to Cd/Ca interaction

Changes of the Ca content in the nutrient solution resulted in an accumulation of this element in the various organs of bean plants (Table 1). Cadmium treatment of younger plants growing in the nutrient solution with a low and high level of Ca caused changes in Ca accumulation and its distribution among the plant organs. In plants growing at a low level of Ca its accumulation increased in roots after 12-day Cd exposure. The roots of Cd-treated plants growing in the nutrient solution with a high

Discussion

The similarity of the physical properties of the ions (a valence, ionic radius) present in the medium can cause disturbances in their uptake and distribution in plants. The possibility of Cd/Ca interaction was given attention by Greger and Lindberg (1987), suggesting that Cd presence in the medium facilitated Ca transport to shoots. Thus, it seemed to us probable that a different calcium content in the medium (essentially not influencing the growth and development of control plants) could

Acknowledgements

This paper is a part of a project supported by the State Committee for Scientific Research (KBN) grant No. 6P04C.037.09. It was also supported by The Swedish Institute and The Swedish Natural Science Research Council.

References (29)

  • D.S Bush

    Calcium regulation in plant cells and its role in signaling

    Annu. Rev. Plant Physiol. Plant Mol. Biol.

    (1995)
  • W.H.O Ernst et al.

    Metal tolerance in plants

    Acta Bot. Neerl.

    (1992)
  • C.H Foyer et al.

    Photooxidative stress in plants

    Physiol. Plant

    (1994)
  • B Genty et al.

    The relationship between non-photochemical quenching of chlorophyll fluorescence and the rate of photosystem 2 photochemistry in leaves

    Photosynth. Res.

    (1990)
  • Cited by (46)

    • Reducing lead uptake by plants as a way to lead-free food

      2023, Ecotoxicology and Environmental Safety
    • Transcription factors involved in plant responses to heavy metal stress adaptation

      2021, Plant Perspectives to Global Climate Changes: Developing Climate-Resilient Plants
    • The Effect of Cd Stress in Mineral Nutrient Uptake in Plants

      2018, Cadmium Toxicity and Tolerance in Plants: From Physiology to Remediation
    • Biomonitoring of airborne particulate matter emitted from a cement plant and comparison with dispersion modelling results

      2014, Atmospheric Environment
      Citation Excerpt :

      Mn, Ni and Cu did not present significant differences between sites, whereas Cd, and Ca were highly enriched in the vicinities of the cement plant. The high correlation between Cd and Ca may be explained by the fact that Cd was taken up by plants, using the paths of Ca transport (Skórzyńska-Polit et al., 1998). It is therefore reasonable to suppose that the presence of Cd in the study area was determined by the Ca levels occurring in plant cells.

    • Excess Ca<sup>2+</sup> does not alleviate but increases the toxicity of Hg<sup>2+</sup> to photosystem II in Synechocystis sp. (Cyanophyta)

      2013, Ecotoxicology and Environmental Safety
      Citation Excerpt :

      This study clearly demonstrated that Ca2+ aggravated the Hg2+-induced toxicity to PSII of Synechocystis sp., which is contrary to the protective role of excess Ca2+ against the toxicity of other heavy metals. A few studies showed excess Ca2+ alleviated the toxicity of heavy metals such as Cu2+ to photosynthetic apparatus (Maksymiec and Baszyński, 1999), Pb2+ (Rashid and Popovic, 1990), Cd2+ (Skorzynska-Polit et al., 1998) and Ni2+ (Ouzounidou et al., 2006). Only one previous study reported similar results.

    View all citing articles on Scopus
    View full text