title: Exogenous malic and acetic acids reduce cadmium phytotoxicity and enhance cadmium accumulation in roots of sunflower plants.
abstract: There is increasing evidence showing that low molecular weight organic acids (LMWOA) are involved in heavy metal resistance mechanisms in plants. The aim of this study was to investigate the effects of exogenous malic (MA) or acetic (AA) acids on the toxicity and accumulation of cadmium (Cd) in sunflower (Helianthus annuus L.). For this purpose, plants were grown in hydroponics under controlled conditions. Single Cd stress (5 μM Cd for 14 days) induced strong phytotoxic effects, as indicated by a decrease in all growth parameters, concentration of photosynthetic pigments, and root activity, as well as a high level of hydrogen peroxide (H2O2) accumulation. Exogenous MA or AA (250 or 500 μM) applied to the Cd-containing medium enhanced the accumulation of Cd by the roots and limited Cd translocation to the shoots. Moreover, the MA or AA applied more or less reduced Cd phytotoxicity by increasing the growth parameters, photosynthetic pigment concentrations, decreasing accumulation of H2O2, and improving the root activity. Of the studied organic acids, MA was much more efficient in mitigation of Cd toxicity than AA, probably by its antioxidant effects, which were stronger than those of AA. Plant response to Cd involved decreased production of endogenous LMWOA, probably as a consequence of severe Cd toxicity. The addition of MA or AA to the medium increased endogenous accumulation of LMWOA, especially in the roots, which could be beneficial for plant metabolism. These results imply that especially MA may be involved in the processes of Cd uptake, translocation, and tolerance in plants.
authors.affiliation: Department of Plant Physiology, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland. Electronic address: bhawrylak@yahoo.com.
authors.forename: Barbara
authors.initials: B
authors.lastname: Hawrylak-Nowak
authors.affiliation: Department of Plant Physiology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.
authors.forename: Sławomir
authors.initials: S
authors.lastname: Dresler
authors.affiliation: Department of Plant Physiology, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland.
authors.forename: Renata
authors.initials: R
authors.lastname: Matraszek
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology*; D002104:Cadmium / Q000633:toxicity*; D006368:Helianthus / Q000378:metabolism*; D008293:Malates / Q000494:pharmacology*; D018517:Plant Roots / Q000378:metabolism*
chemical_list: D008293:Malates; D002104:Cadmium; C030298:malic acid; D019342:Acetic Acid
keywords: Cadmium; Heavy metal tolerance; Helianthus annuus L.; Organic acids