title: Cadmium spiked soil modulates root organic acids exudation and ionic contents of two differentially Cd tolerant maize (Zea mays L.) cultivars.
abstract: Our earlier work described that the roots of two maize cultivars, grown hydroponically, differentially responded to cadmium (Cd) stress by initiating changes in medium pH depending on their Cd tolerance. The current study investigated the root exudation, elemental contents and antioxidant behavior of the same maize cultivars [cv. 3062 (Cd-tolerant) and cv. 31P41 (Cd-sensitive)] under Cd stress. Plants were maintained in a rhizobox-like system carrying soil spiked with Cd concentrations of 0, 10, 20, 30, 40 and 50 μmol/kg soil. The root and shoot Cd contents increased, while Mg, Ca and Fe contents mainly decreased at higher Cd levels, and preferentially in the sensitive cultivar. Interestingly, the K contents increased in roots of cv. 3062 at low Cd treatments. The Cd stress caused acidosis of the maize root exudates predominantly in cv. 3062. The concentration of various organic acids was significantly increased in the root exudates of cv. 3062 with applied Cd levels. This effect was diminished in cv. 31P41 at higher Cd levels. Cd exposure increased the relative membrane permeability, anthocyanin (only in cv. 3062), proline contents and the activities of peroxidases (POD) and superoxide dismutase (SOD). The only exception was the catalase activity, which was diminished in both cultivars. Root Cd contents were positively correlated with the secretion of acetic acid, oxalic acid, glutamic acid, citric acid, and succinic acid. The antioxidants like POD and SOD exhibited a positive correlation with the organic acids under Cd stress. It is likly that a high exudation of dicarboxylic organic acids improves nutrient uptake and activities of antioxidants, which enables the tolerant cultivar to acclimatize in Cd polluted environment.
authors.affiliation: Department of Botany, Government College University, Faisalabad 38000, Pakistan. Electronic address: mtariqjaved@gcuf.edu.pk.
authors.forename: M Tariq
authors.initials: MT
authors.lastname: Javed
authors.affiliation: Department of Botany, Government College University, Faisalabad 38000, Pakistan.
authors.forename: M Sohail
authors.initials: MS
authors.lastname: Akram
authors.affiliation: Department of Botany, Government College University, Faisalabad 38000, Pakistan.
authors.forename: Kashif
authors.initials: K
authors.lastname: Tanwir
authors.affiliation: Department of Plant Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan.
authors.forename: Hassan
authors.initials: H
authors.lastname: Javed Chaudhary
authors.affiliation: Department of Botany, Government College University, Faisalabad 38000, Pakistan.
authors.forename: Qasim
authors.initials: Q
authors.lastname: Ali
authors.affiliation: The Rural Economy and Agricultural Society, Örebro 701 45, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Stoltz
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm 10691, Sweden.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Lindberg
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001692:Biological Transport; D002104:Cadmium / Q000032:analysis / Q000633:toxicity*; D002264:Carboxylic Acids / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D018384:Oxidative Stress / Q000187:drug effects; D010544:Peroxidases / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000633:toxicity*; D013482:Superoxide Dismutase / Q000378:metabolism; D003313:Zea mays / Q000254:growth & development* / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002264:Carboxylic Acids; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D018698:Glutamic Acid; D010544:Peroxidases; D013482:Superoxide Dismutase
keywords: Cd tolerance; Rhizobox; Rhizosphere; Root exudates; Zea mays