Applying foliar magnesium enhances wheat growth in acidic soil by stimulating exudation of malate and citrate

Abstract

Aims Aluminium 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. Methods Two 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 2 O). 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. Results Applying 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 ma-late 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. Conclusions Increased malate and citrate exudation is the underlying mechanism of enhanced wheat growth following foliar Mg application under acidic soil conditions.

Exogenous silicon induces aluminum tolerance in white clover (Trifolium repens) by reducing aluminum uptake and enhancing organic acid secretion

“…Moreover, these inorganic ions were crucial for Al’s detoxification process. According to the study, Mg 2+ and K + can help release organic acid anions and maintain electrolyte balance ( Kibria, Barton & Rengel, 2021 ). By increasing Mg uptake, the overexpression of the Mg transporter gene AtMGT1 reduced Al toxicity ( Deng et al, 2006 ).…”

Evaluating Leaf Wettability and Salt Hygroscopicity as Drivers for Foliar Absorption

“…Foliar sprays are often applied to crop species in many areas of the world [ 20 , 21 , 22 , 23 , 24 ], but the response of plants to the treatments is often variable as described for other elements [ 17 , 19 ]. Hence, specific trials are required for attempting to clarify which are the major factors influencing the absorption of foliar agrochemical treatments as a prerequisite for optimizing the efficacy of foliar sprays in the future.…”

“…Despite leaf wettability being an important preliminary variable affecting foliar absorption, transport across the leaf epidermis may also be limited by the physico-chemical nature of the cuticle and cell wall [ 18 ]. Various studies carried out with different crop species reported positive plant responses and increased tissue Mg values in association with the application of foliar Mg sprays, e.g., [ 20 , 21 , 22 , 23 , 24 ].…”

Citric Acid Inhibits Cd Absorption and Transportation by Improving the Antagonism of Essential Elements in Rice Organs

“…Research has shown that citric acid-modified biochar can reduce the bioavailability of Cd in soil [ 10 ]. Citric acid could regulate the balance of anions and cations in rice by mediating the balance of cations and anions within plants and subsequently affecting the transport of mineral elements within plant tissues [ 11 , 12 ]. Exposed to 50 μM Cr stress, the CA content significantly increased in rice.…”