Toxicity of MCPA on non-green potato tuber calli

Abstract

Growth of potato tuber calli cells (non-green) is inhibited by 4-chloro-2-methylphenoxyacetic acid (MCPA) as a consequence of perturbation of membrane integrity. MCPA also depresses ATP content with simultaneous increase of ADP and AMP, i.e., the energy charge is severely compromised. Cell redox state is also affected by MCPA, as a function of concentration. Up to 60 lM, MCPA stimulates glutathione reductase and glutathione transferase, whereas superoxide dismutase and catalase activities are not affected. However, 120 lM MCPA inhibits all these activities. Cell death challenged by MCPA is putatively related to disturbance of membrane integrity responsible for mitochondrial uncoupling with decrease of the energy charge and subsequent loss of ions and metabolites.

The combined effects of UV-B radiation and herbicides on photosynthesis, antioxidant enzymes and DNA damage in two bloom-forming cyanobacteria

“…This was proved by measuring dsDNA content and photosynthetic activity in this study (Table 3). MCPA is an artificial auxin-hormone which stimulates plant growth by increasing cell extension and cell differentiation (Copping and Hewitt 1998;Peixoto et al, 2009). MCPA usually causes strong cell growth stimulation or DNA damage resulting in plant death (Hopkins, 1999;Copping and Hewitt, 1998;Nielsen and Dahllöf, 2007).…”

“…The damage induced by MCPA and GPS could not be restored during the recovery process. This damage was due to the synthesis of DNA and proteins by MCPA (Peixoto et al, 2009), or inhibition of the activity of 5-enolpyruvylshikimate-3-phosphate synthase by GPS (Lipok et al, 2010). DCMU can block the electron transport in the RC complex from plastoquinone QA À to plastoquinone QB À (Krause and Weis, 1984;Xia et al, 2004).…”

Herbicides: the Face and the Reverse of the Coin. An in Vitro Approach to the Toxicity of Herbicides in Non-Target Organisms

“…The growth of nongreen callus tissue in the dark precludes the analysis of herbicide effects on the photosynthetic system, but allows to address studies to other putative targets of the toxic action of those compounds, such as mitochondria which have a crucial role in ATP synthesis in these cells devoid of chlorophyl. Thus, potato callus tissue has been used as a relevant material source for in vivo and ex vivo studies of herbicide toxicity at the mitochondrial level (Peixoto et al, 2008;2009a). In summary, plant cell cultures have been established as a good alternative model for ecotoxicological evaluation and also as a means to study herbicide mechanisms of action and metabolism in plants (Harms, 1992).…”

“…The cytotoxic effects of the herbicides dicamba, 2,4-D and MCPA on cell cultures of potato tuber calli (S. tuberousum L.) were evaluated upon exposition to the herbicides for a period of 4 weeks, by monitoring the changes in cell growth, membrane integrity, energy charge, cell redox state and activity of several antioxidant enzymes, in studies parallel to those previously referred for paraquat (Peixoto et al, 2008;2009a). Regarding the cell growth, the concentrations at which herbicides inhibited growth by 50% (IC 50 ) were 59, 50 and 20 µM for MCPA, dicamba and 2,4-D, respectively.…”

“…Into the cell, the esterified molecules undergo hydrolysis by intracellular esterases, generating fluorescein, which fluoresces by exposure to short wavelength light (Prosperi, 1990). Therefore, viable cells containing fluorescein can be observed by fluorescence microscopy (Peixoto et al, 2009a). When the membrane is disrupted, fluorescein is released occurring an increase of extracellular fluorescence, detected by microscopy or by the spectrometric method.…”