Extraction and Quantification of Rhizosphere Organic Acids

The dug roots were gradually agitated to isolate them from the bulk soils in order to acquire the rhizosphere. The levels citric acid, oxalic acid, and phenolic content were measured [54 (link),55 (link)]. Using ribitol as an internal standard, organic acids (citric and oxalic acids) were collected in 0.1% phosphoric acid that also included butylated hydroxyanisole. As stated by de Sousa et al. [54 (link)], filtrates were employed for HPLC quantification using a LaChrom L-7455 diode array (Merck-Hitachi, Barcelona, Spain) after centrifugation. According to Zhang et al. [56 (link)], the phenolic content was spectrophotometrically estimated (Shimadzu UV-Vis 1601 PC, Kyoto, Japan).