Effect of cadmium, chromium, and lead on micropropagation and physio-biochemical parameters of Bacopa monnieri (L.) Wettst. cultured in vitro

Heavy metals are released into the environment as a result of anthropogenic activities such as melting metallic ores, industrial productions, power stations, and pesticides. Among these, cadmium (Cd), chromium (Cr) and lead (Pb) are the most common heavy metals in the environment and can cause serious toxic effects on both animals and plants. In this study, the effect of Cd, Cr, and Pb on the propagation of Bacopa monnieri (L.) Wettst. by tissue culture was investigated. In addition, various physio-biochemical parameters (photosynthetic pigments contents, protein contents, lipid peroxidation, and hydrogen peroxide) and survival frequency of the plant were evaluated. The shoot tip explants of B. monnieri were cultured in Murashige and Skoog (MS) nutrient media supplemented with 0.50 mg/L 6-benzylaminopurine (BAP) and different concentrations of Cd, Cr, and Pb (0.25–1.00 mg/kg) for 10 weeks. 100% shoot regeneration was determined in MS medium containing 0.25, 0.50, and 0.75 mg/kg Cd, 0.25 mg/kg Cr and 0.25 and 0.50 mg/kg Pb. Mean number of shoots per explant and shoot lengths decreased significantly with increasing metal concentration. In Cd, Cr, and Pb applications, maximum number of shoots per explant was obtained as 30.52, 22.47, and 27.12 shoot/explant and the highest shoot lengths were determined as 4.16, 4.27, and 4.35 cm, respectively. As the concentration of the metal exposed to the explant increased, the photosynthetic pigment contents of the plant decreased. The negative impact of metals on photosynthetic pigment contents was found to increase in the order: Cd < Cr < Pb. Similarly, the protein content of plants also decreased due to the negative effect of metals. On the other hand, malondialdehyde (MDA) and hydrogen peroxide (H2O2) values elevated with increasing concentrations of heavy metals. The findings of this study carried out under in vitro conditions may shed light on researchers who want to investigate the effects of heavy metals on plants.