Combined effect of organic acids and flavonoids on the mobilization of major and trace elements from soil

Abstract

Combinations of different molecules usually co-exuded by plant roots in soil can significantly affect the mobilization of mineral elements from soil. The flavonoids rutin and quercetin appeared to be highly efficient in Fe and Mn mobilization from soil, being rutin about 25 times more effective than citrate in extracting Fe from an alkaline calcareous soil, and 15 times in mobilizing Mn from a slight acidic agricultural soil. Quercetin was particularly effective in mobilizing Mn from the acidic soil and 50 times more efficient than citrate. A significant synergistic effect was detected when either quercetin or rutin was combined with citrate, extracting, respectively, 1.7 and 1.5 times more Mn than what is expected by a simple combination of the two. Sorption processes on soil particles were more relevant for flavonoids than for organic acids for which microbial degradation often prevails, with the only exception of oxalate. Citrate was usually the most efficient organic acid in mobilizing major and trace elements from soil even if oxalate was a better extractant for Cu, Zn, and Ni from the alkaline soil. In the acid soil, a synergistic effect among organic acids was observed only for Mn while in alkaline soil it was observed for Si. The mechanism by which Fe is extracted by rutin in the alkaline soil is a reductive one, with one molecule of rutin being capable of mobilizing two atoms of Fe. Also for Mn in the acid soil, quercetin and rutin solubilize this element by a reductive process. However, when quercetin and rutin are combined with citrate, a complex-forming dissolution mechanism also occurs which increases the mobilization of Mn over the expected rates

Effect of canola rhizosphere and silicate dissolving bacteria on the weathering and K release from indigenous glauconite shale

“…Synergistic effect could exist among exudates and also between exudates and nutrient, and this might affect nutrient mobilization , for example, under acidic condition, the synergistic effect among organic acid was observed for Mn, while in alkaline condition, it was observed for Si (Terzano et al 2015).…”

Differential Impact of Plant Secondary Metabolites on the Soil Microbiota

“…Studies on the accumulation or degradation of gramine in soil or on the absorption to soil particles are not available. It is known that quercetin strongly interacts with and is adsorbed by soil particles (Terzano et al, 2015). In addition, quercetin is rapidly degraded by soil bacteria, e.g., Pseudomonas putida strains (Pillai and Swarup, 2002).…”

Single and Combined Fe and S Deficiency Differentially Modulate Root Exudate Composition in Tomato: A Double Strategy for Fe Acquisition?

“…[24,25]. In this respect, the enhanced exudation of organic ligands like phytosiderophores (PS) and organic acids with a high affinity for elements/metals (such as Fe) can also have a very positive impact on the metal mobilization (mineral weathering) [19,[26][27][28]. With respect to the organic acids, it should be mentioned that they can also impact the rhizosphere processes and the fertility levels of this soil volume through their direct effect on the microbial biomass and its activity [29,30].…”