The Effects of Cadmium-Zinc Interactions on Biochemical Responses in Tobacco Seedlings and Adult Plants

Abstract

The objective of the present study was to investigate the effects of cadmium-zinc (Cd-Zn) interactions on their uptake, oxidative damage of cell macromolecules (lipids, proteins, DNA) and activities of antioxidative enzymes in tobacco seedlings as well as roots and leaves of adult plants. Seedlings and plants were exposed to Cd (10 µM and 15 µM) and Zn (25 µM and 50 µM) as well as their combinations (10 µM or 15 µM Cd with either 25 µM or 50 µM Zn). Measurement of metal accumulation exhibited that Zn had mostly positive effect on Cd uptake in roots and seedlings, while Cd had antagonistic effect on Zn uptake in leaves and roots. According to examined oxidative stress parameters, in seedlings and roots individual Cd treatments induced oxidative damage, which was less prominent in combined treatments, indicating that the presence of Zn alleviates oxidative stress. However, DNA damage found in seedlings, and lower glutathione reductase (GR) and superoxide dismutase (SOD) activity recorded in both seedlings and roots, after individual Zn treatments, indicate that Zn accumulation could impose toxic effects. In leaves, oxidative stress was found after exposure to Cd either alone or in combination with Zn, thus implying that in this tissue Zn did not have alleviating effects. In conclusion, results obtained in different tobacco tissues suggest tissue-dependent Cd-Zn interactions, which resulted in activation of different mechanisms involved in the protection against metal stress.

Growth and photosynthetic responses of Lemna minor L. exposed to cadmium in combination with zinc or copper / Rast i fotosinteza u vodene leće (Lemna minor L.) izložene kadmiju u kombinaciji s cinkom ili bakrom

“…Therefore, our findings support previous observations by Cvjetko et al (32) on Cu ability to induce oxidative stress and affect the photosynthetic apparatus in duckweed. Reduction of Cd-induced stress by Zn is probably mediated through lowering Cd uptake, which is in agreement with the results obtained for C. demersum (29) and tobacco (56). Interestingly, PCA did not show substantial subgrouping of the plant responses based on the treatment duration, except for the plants exposed to single Zn treatment.…”

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“…The synergistic rather than the expected antagonistic effect detected with the Cd + Zn mixture confirms that its toxicity cannot be predicted from the toxic effect of its single components, because their joint effect may be synergistic or antagonistic, depending on the species on which the mixture is tested, and even on the organ or tissue used for this test (Tkalec et al, 2014). The duration of exposure to sublethal concentrations of a xenobiotic is expected to increase its toxic effect (Newman and McCloskey, 1996).…”

“…An antagonistic effect of Zn and Cd was described in some plant organisms, but it was found to be either concentration dependent (Sharma et al, 1999) or even restricted to some type of tissue (Tkalec et al, 2014). However, these same authors described also synergistic effects, either in different tissues or when one of the toxicants exceeded a critical level.…”

Growth and Biochemical Responses on Corn Plants Cultivated in Soils Contaminated With Cadmium and Zinc

“…The biological effects of individual trace elements are well documented, and although the combinations between them are usual in nature, the mixed effects still need further investigations (Tkalec et al, 2014). The Cd often follows Zn minerals in the environment due to its chemical and physical resemblances (Gallego et al, 2012).…”

“…All trace elements, essential and non-essential, when present in concentrations higher than optimum will affect different cellular components, interfering and disturbing the homeostasis of the plant cell straight through the accumulation of reactive oxygen species (ROS) (Tkalec et al, 2014). Toxic levels of ROS can generate oxidative stress, leading to inactivation and damage of the proteins and lipids on the cell membrane (Sharma et al, 2012).…”