Effect of metabolic regulators on aluminium uptake and toxicity in Matricaria chamomilla plants

Phenolic metabolism of Al-exposed Matricaria chamomilla plants was modulated with four regulators: 2-aminoindane-2-phosphonic acid (AIP), salicylic acid (SA), sodium nitroprusside (SNP) and dithiothreitol (DTT). Physiological parameters (tissue water content, soluble proteins, reducing sugars, K+ content), root lignin content and free amino acids (increase in root proline and alanine) were the most affected in SA + Al variant, indicating negative impact of SA on Al-induced changes. SNP showed the least visible impact, suggesting protective effect of nitric oxide. Complex comparison between Al alone and combined treatments revealed that SA and DTT stimulated increase in shoot phenolic acids (mainly vanillic acid), sum of flavonols and soluble phenols but decreased the levels of coumarin-related compounds (Z- and E-2-ك-d-glucopyranosyloxy-4-methoxycinnamic acids), leading to elevation of shoot Al. Positive correlation between phenolic acids (mainly ferulic and chlorogenic acids), soluble phenols and total Al was found in the roots of SA and DTT variants. These events were not observed in AIP and SNP treatments. These data, to our knowledge for the first time, exactly confirm that phenolic metabolites may affect shoot Al uptake and this relation is rather positive in terms of simple phenols (and negative in terms of coumarin-related compounds).