Paper
Applying foliar magnesium enhances wheat growth in acidic soil by stimulating exudation of malate and citrate
Published May 1, 2021 · M. Kibria, L. Barton, Z. Rengel
Plant and Soil
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Abstract
AimsAluminium toxicity in acidic soils adversely affects wheat growth. Foliar-applied magnesium (Mg) contributes to mitigating soil acidity stress in wheat, but the mechanisms are unknown. This study explored the mechanism of foliar-Mg mediated enhancement of wheat growth in acidic soil.MethodsTwo contrasting near-isogenic wheat (Triticum aestivum L.) genotypes differing in Al resistance (Al-sensitive ES8 and Al-resistant ET8) were grown to the vegetative stage (Zadoks 24) in a reconstituted acidic soil (pH_0.1 M CaCl2 4.0) profile with three rates of foliar Mg (0, 200 and 500 mg Mg L^− 1 using MgSO_4.7H_2O). Magnesium was applied to the foliage twice [14 and 28 days after sowing (DAS)], and plant growth and root exuded carboxylates were measured up to 42 DAS.ResultsApplying 200 mg Mg L^− 1 to the foliage increased organic acid anion exudation from wheat roots by ~ 2-fold compared to 0 foliar Mg treated plants. The Al-resistant wheat genotype exuded 1.3-fold more malate and citrate from roots than the Al-sensitive genotype in the absence of foliar Mg. Malate exudation was delayed relative to citrate following foliar Mg application. The foliar-applied Mg increased shoot and root dry weight (by ~ 38 %), total root length (by ~ 33 %) and intrinsic water-use efficiency (by ~ 80 %) compared to plants treated with no Mg. Applying foliar Mg decreased soil acidity stress (as shown by a significant increase in chlorophyll fluorescence Fv/Fm ratio) in wheat compared to 0 foliar Mg.ConclusionsIncreased malate and citrate exudation is the underlying mechanism of enhanced wheat growth following foliar Mg application under acidic soil conditions.
Foliar magnesium application enhances wheat growth in acidic soil by increasing malate and citrate exudation, reducing soil acidity stress.
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