Impact of mannitol and poly ethylene glycol 6000 induced water deficit on plant biomass and major secondary metabolites in Centella asiatica (L.) Urb. in vitro

Abstract

Low water potential related stresses are regulated by modifying water uptake and loss to avoid low water potential, accumulating solutes which in turn enhance active principles and its gene expressions. Present study examined effect of in vitro induced absorption of mannitol and PEG (poly ethelene glycol) 6000 in Indian pennywort, Centella asiatica (L.) Urb., neutraceutical plant, evidenced by phenotypic, molecular and phytochemical analyses. Both mannitol and PEG 6000 induce water deficit conditions in plants and retarded normal plant biomass in terms of fresh and dry weights. These effects were significantly less severe in plants subjected to mannitol, compared to PEG. PEG and mannitol imposed water deficit, resulted in decline in major active compound, asiaticoside evidenced by HPTLC of asiaticoside content. Differential expression of some selected key genes in the asiaticoside pathway including squalene synthase and β amyrin synthase by qPCR, confirmed decrease in transcript level expression of asiaticoside, whereas upregulated transcript level expression was observed in cycloartenol synthase for synthesis of phytosterols. Estimation of total flavonoids and phenolics under different water deficit conditions were found declined. In conclusion, water deficit by mannitol and PEG 6000 can significantly affects processes associated with biomass growth and ability to synthesize secondary metabolites in C. asiatica.