Interference of Heavy Metal Toxicity with Auxin Physiology

Elobeid, Mudawi M.; Polle, Andrea

doi:10.1007/978-3-642-22081-4_12

Cited by 14 publications

(10 citation statements)

References 56 publications

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“…This finding is in agreement with the data presented by Schopfer et al [32], who documented that the presence of oxygen reactive species (ROS) (e.g., H 2 O 2 ) in the cell wall is necessary to promote the auxin-induced growth of coleoptile sections. Most investigations have shown that treating plants with heavy metals decreases the content of IAA in plants, see [33] and literature therein [34][35][36][37][38][39]. In the current study, we found that Pb and Cd increased the content of IAA in the corn coleoptile sections, but only at the concentrations at which stimulation of elongation growth was observed ( Figure 1).…”

Section: Discussionsupporting

confidence: 63%

Hormesis in Plants: The Role of Oxidative Stress, Auxins and Photosynthesis in Corn Treated with Cd or Pb

Małkowski

Sitko

Szopiński

et al. 2020

IJMS

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Hormesis, which describes the stimulatory effect of low doses of toxic substances on growth, is a well-known phenomenon in the plant and animal kingdoms. However, the mechanisms that are involved in this phenomenon are still poorly understood. We performed preliminary studies on corn coleoptile sections, which showed a positive correlation between the stimulation of growth by Cd or Pb and an increase in the auxin and H 2 O 2 content in the coleoptile sections. Subsequently, we grew corn seedlings in hydroponic culture and tested a wide range of Cd or Pb concentrations in order to determine hormetic growth stimulation. In these seedlings the gas exchange and the chlorophyll a fluorescence, as well as the content of chlorophyll, flavonol, auxin and hydrogen peroxide, were measured. We found that during the hormetic stimulation of growth, the response of the photosynthetic apparatus to Cd and Pb differed significantly. While the application of Cd mostly caused a decrease in various photosynthetic parameters, the application of Pb stimulated some of them. Nevertheless, we discovered that the common features of the hormetic stimulation of shoot growth by heavy metals are an increase in the auxin and flavonol content and the maintenance of hydrogen peroxide at the same level as the control plants.

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Section: Discussionsupporting

confidence: 63%

Hormesis in Plants: The Role of Oxidative Stress, Auxins and Photosynthesis in Corn Treated with Cd or Pb

Małkowski

Sitko

Szopiński

et al. 2020

IJMS

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“…The basipetal transport of auxin through the rhizodermal and outer cortical cells plays an important role in cell elongation . Interestingly, several studies have recently indicated that auxin may be involved in the expression of Al toxicity . Other mechanistic pathways, both direct and indirect, are possible also.…”

Section: A Hypothesismentioning

confidence: 99%

The rhizotoxicity of metal cations is related to their strength of binding to hard ligands

Kopittke

Menzies

Wang

et al. 2014

Enviro Toxic and Chemistry

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Mechanisms whereby metal cations are toxic to plant roots remain largely unknown. Aluminum, for example, has been recognized as rhizotoxic for approximately 100 yr, but there is no consensus on its mode of action. The authors contend that the primary mechanism of rhizotoxicity of many metal cations is nonspecific and that the magnitude of toxic effects is positively related to the strength with which they bind to hard ligands, especially carboxylate ligands of the cell-wall pectic matrix. Specifically, the authors propose that metal cations have a common toxic mechanism through inhibiting the controlled relaxation of the cell wall as required for elongation. Metal cations such as Al 3þ and Hg 2þ , which bind strongly to hard ligands, are toxic at relatively low concentrations because they bind strongly to the walls of cells in the rhizodermis and outer cortex of the root elongation zone with little movement into the inner tissues. In contrast, metal cations such as Ca 2þ , Na þ , Mn 2þ , and Zn 2þ , which bind weakly to hard ligands, bind only weakly to the cell wall and move farther into the root cylinder. Only at high concentrations is their weak binding sufficient to inhibit the relaxation of the cell wall. Finally, different mechanisms would explain why certain metal cations (for example, Tl þ , Ag þ , Cs þ , and Cu 2þ ) are sometimes more toxic than expected through binding to hard ligands. The data presented in the present study demonstrate the importance of strength of binding to hard ligands in influencing a range of important physiological processes within roots through nonspecific mechanisms. Environ Toxicol Chem 2014;33:268-277. # 2013 SETAC

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“…Auxin oxidases not only increase the degradation of auxin, but also decrease the activities of many genes involved in plant growth processes. Coordination of plant growth and defense is controlled by auxins (Elobeid and Polle, 2012). Hence to reduce the toxic effects of heavy metals on plant growth, the exogenous application of plant hormones is recently gaining importance (Hare et al, 1997;Ali et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Auxin-mediated growth of rice in cadmium-contaminated soil

Farooq¹,

Asghar²,

Khan³

et al. 2015

Turk J Agric For

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Pollution from heavy metals is a global problem that is very dangerous to the environment. Among the heavy metals, cadmium is receiving more and more attention because it is one of the most ecotoxic, making it very harmful for biological activity in soil, biodiversity, plant metabolism, and human and animal health. Phytohormones, produced by plants, control or regulate germination, growth, metabolism, or other physiological activities, and they can alleviate the toxic effects of heavy metals on plant growth. Auxin is the most abundant natural growth hormone, controlling apical dominance, tropism, elongation of shoots, and initiation of roots in plants. However, cadmium stress causes the degradation of indigenous auxin. To cope with this, auxin may be applied exogenously. To evaluate the role of auxin in cadmium -contaminated soil, different levels of the auxin precursor L-TRP were applied to plants growing in contaminated soil. Rice seedlings were dipped in a L-TRP solution for 2 h and transplanted into potted soil contaminated with 30 mg kg -1 cadmium. The results showed that the exogenous application of L-TRP improved the growth and yield of treated plants both in normal and contaminated soil. The data of different parameters showed that L-TRP enhanced plant height (12.54%), the number of tillers (25.53%), the number of panicles (19.04%), the 1000 grain weight (19.28%), and the paddy yield (11.78%) in cadmiumcontaminated soil, as compared to plants grown in the absence of L-TRP with the same level of contamination. L-TRP increased the uptake of cadmium in rice straw while decreasing the translocation of cadmium towards grains, as compared to plants grown in contaminated soil without L-TRP. This experiment revealed the possibility of using L-TRP to improve plant growth and soil health in contaminated soil.

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Interference of Heavy Metal Toxicity with Auxin Physiology

Cited by 14 publications

References 56 publications

Hormesis in Plants: The Role of Oxidative Stress, Auxins and Photosynthesis in Corn Treated with Cd or Pb

Hormesis in Plants: The Role of Oxidative Stress, Auxins and Photosynthesis in Corn Treated with Cd or Pb

The rhizotoxicity of metal cations is related to their strength of binding to hard ligands

Auxin-mediated growth of rice in cadmium-contaminated soil

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