Timing, location and crop species influence the magnitude of amelioration of aluminum toxicity by magnesium

Revista Brasileira de Ciência do Solo

Ivo Ribeiro Silva²  Tarcísio Fernando Cortes Corrêa²  Roberto Ferreira Novais²  T. Jot Smyth¹  Thomas Rufty¹  Eulene Francisco Silva²  Fabrício Oliveira Gebrim²  Flancer Novais Nunes² 

[1] ,Federal University of Viçosa Soil Science Department Viçosa MG ,Brazil

关键词: soybean;    cations;    calcium;    rhizotoxicity;    soil acidity;    soja;    cátions;    rizotoxidez;    acidez do solo;   

DOI  :  10.1590/S0100-06832009000100007

来源: SciELO

【 摘 要 】

The protective effect of cations, especially Ca and Mg, against aluminum (Al) rhizotoxicity has been extensively investigated in the last decades. The mechanisms by which the process occurs are however only beginning to be elucidated. Six experiments were carried out here to characterize the protective effect of Mg application in relation to timing, location and crop specificity: Experiment 1 - Protective effect of Mg compared to Ca; Experiment 2 - Protective effect of Mg on distinct root classes of 15 soybean genotypes; Experiment 3 - Effect of timing of Mg supply on the response of soybean cvs. to Al; Experiment 4 - Investigating whether the Mg protective effect is apoplastic or simplastic using a split-root system; Experiment 5 - Protective effect of Mg supplied in solution or foliar spraying, and Experiment 6 - Protective effect of Mg on Al rhizotoxicity in other crops. It was found that the addition of 50 mmol L-1 Mg to solutions containing toxic Al increased Al tolerance in 15 soybean cultivars. This caused soybean cultivars known as Al-sensitive to behave as if they were tolerant. The protective action of Mg seems to require constant Mg supply in the external medium. Supplying Mg up to 6 h after root exposition to Al was sufficient to maintain normal soybean root growth, but root growth was not recovered by Mg addition 12 h after Al treatments. Mg application to half of the root system not exposed to Al was not sufficient to prevent Al toxicity on the other half exposed to Al without Mg in rooting medium, indicating the existence of an external protection mechanism of Mg. Foliar spraying with Mg also failed to decrease Al toxicity, indicating a possible apoplastic role of Mg. The protective effect of Mg appeared to be soybean-specific since Mg supply did not substantially improve root elongation in sorghum, wheat, corn, cotton, rice, or snap bean when grown in the presence of toxic Al concentrations.

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