Enhancement of compatible solute and secondary metabolites production in Plantago ovata Forsk. by salinity stress

Accumulation of toxic ions in plant tissues modulates the levels of primary and secondary metabolites, which may be related to salinity tolerance. In this study, the effects of salt stress (0 to 300 mM) on proline and secondary metabolites (total flavonoids and total saponins) of Plantago ovata (Isabgol) were investigated. This experiment was conducted hydroponically in a NaCl spiked solution. The results indicated a significant increase in proline, total flavonoids and total saponins with the enlargement of NaCl in the medium. Increase in proline content suggests that compatible solutes may contribute to osmotic adjustment at the cellular level and enzyme protection stabilizing the structure of macromolecules and organelles. Increase in total saponins and total flavonoids suggest that the presence of these metabolites is related to increased salt tolerance of P. ovata. The increased synthesis of saponins and flavonoids seems to protect P. ovata from ion-induced oxidative stress, probably due to a common structural skeleton; the phenyl group of those metabolites. Collectively, our results indicate that P. ovata has physiological traits associated with resistance to salinity through accumulation of secondary metabolites to relative high levels and it can be useful for growing, in saline contaminated sites.