Silicon Application Enhances the Photosynthetic Pigments and Phenolic/Flavonoid Content by Modulating the Phenylpropanoid Pathway in Common Buckwheat under Aluminium Stress

Silicon (Si) is very effective in the amelioration of heavy metal (HM) stress in different crop plants. This investigation was conducted to assess the protective role of Si in modulating aluminium (Al) uptake in 21 days old common buckwheat ( Fagopyrum esculentum M.) plants. Exogenous Si (0.5 and 1 mM) treatments were used to study the effect on chlorophyll contents, anthocyanins, total phenolic content (TPC), total flavonoid content (TFC) and defence enzymes (phenylalanine ammonialyase (PAL), tyrosine ammonia lyase (TAL) and polyphenol oxidase (PPO) activities) against Al (0.2 and 0.4 mM) treatments. Results indicated that Al phytotoxicity negatively affected the above mentioned parameters while as Si application markedly reduced the phytotoxicity caused by Al 3+ ions by improving their contents and increasing defense enzyme activities. Si thus alleviates phytotoxicity caused by Al ions and also promotes the production of phenolic and flavonoid compounds by stimulating the phenylpropanoid pathway. The present study revealed that exogenous Si application influenced the phenylpropanoid pathway in common buckwheat irrespective of being an Al tolerant plant thereby decreasing the oxidative damage and enhancing free radical scavenging activity by increasing the production of phenolic and flavonoid compounds under Al stress.