Effects of foliar application of organic acids on alleviation of aluminum toxicity in alfalfa

Abstract

Organic acids (OA) may affect plant resistance to aluminum (Al) toxicity in acidic soils. However, limited information is available on the effects of different organic acids on Al resistance in alfalfa. We investigated the effects of foliar application of organic acids (succinic acid, citric acid, malic acid, and oxalic acid) to alfalfa (Medicago sativa L.) under Al stress. Seedlings were grown in pH 4.5 nutrient solution containing Al at 0 or 100 μM, and were sprayed with water or 100 μM of oxalic acid, malic acid, citric acid, or succinic acid every 3 d during a 10 d experiment. Aluminum stress caused significant reduction in alfalfa growth (reflected by above‐ground biomass, root weight and root length), root activity, mineral nutrient concentrations (Ca, K, Mg, Mn and Zn), and a significant increase in leaf membrane lipid peroxidation. Foliar application of the four organic acids, especially succinic acid, alleviated Al toxicity, as demonstrated by the increase in plant growth and root activity, as well as reduction in lipid peroxidation. Oxalic acid and malic acid treatments significantly increased oxalate exudation and decreased Al concentration in roots exposed to Al stress. Succinic acid treatment significantly increased accumulation of all four organic acids in roots, accumulation of Ca, K, Mg, Mn and Zn, and up‐regulated the gene transcription of malate dehydrogenase (MDH) and phosphoenolpyruvate carboxylase (PEPC) in roots. Our results suggest that the promotion of oxalate exudation from roots through exogenous application of oxalate and malate could contribute to the improvement in Al resistance of alfalfa, and the positive effects of exogenous application of succinate on Al resistance may be associated with the increased endogenous accumulation of all four organic acids in roots, which may constitute an organic‐acid detoxification system in alfalfa.

Gene Expression Analysis of Alfalfa Seedlings Response to Acid-Aluminum

“…The gene expression changes induced by Al would affect the synthesis of succinyl-CoA and in turn influenced OA synthesis in the TCA (tricarboxylic acid) cycle. An et al [10] investigated that Al could affect the synthesis of OAs by influencing the TCA cycle, and the foliar application of succinic acid could increase the accumulation of organic acids (including oxalic acid, malic acid, citric acid, and succinic acid) and alleviate Al toxicity.…”

“…Most reports have suggested that organic acids (OAs) play an important role in the mechanism by which plants tolerate Al stress [10]. Plants also have other mechanisms to cope with Al stress.…”

Changes in the essential oil content and selected traits of sweet basil (Ocimum basilicum L.) as induced by foliar sprays of citric acid and salicylic acid

“…It is suggested that mineral absorption could be affected by elevated exudation of organic acids in response to foliar organic acids (Jaafari and Hadavi, 2012). However this is confirmed recently by An et al (2014), and the intervention of these exudates in mineral absorption in the soil is well known (Bais et al, 2006;Arcand and Schneider, 2006;Marschener, 1998).…”

“…Jafari and Hadavi (2012), suggested an increase in mineral absorption by elevated exudation of organic acids in response to foliar organic acids as part of mechanism responsible for improved growth parameters. This was confirmed recently by An et al (2014), and the mediation of these exudates in mineral absorption in the soil medium is well known (Marschener, 1998;Bais et al, 2006;Arcand and Schneider, 2006). In addition, the exudated organic acids are the main carbon source for rhizobacteria (Ohwaki and Sugahara, 1997).…”

Morpho-physiological and biochemical responses of bladder cherry (Physalis alkekengi L.) induced by multienzymatic biostimulant, IBA, and citric acid

“…Organic acids are involved in a broad range of physiological processes of plant growth and development (An et al, 2014), and are also considered to alleviate biotic stresses (Jafari and Hadavi, 2012). Endogenous organic acids are the source of both carbon skeleton and energy for cells, and are used in the respiratory cycle and other biochemical pathways.…”