Paraquat (methyl viologen) toxicity in Centella asiatica callus cultures
2006
Misri Kusnan | Norhayati Yusuf | Siti Khalijah Daud | Nor’Aini Mohd Fadzillah | Marziah Mahmood
The effect of paraquat (PQ) treatment on growth, cell viability, hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels were investigated in the callus of two Centella asiatica accessions (CA03 and CA09). Callus of C. asiatica were treated with 50uM PQ for five days in Murashige and Skoog (MS) liquid medium. Callus growth, viability of the callus as well as H 2O2 content and MDA levels were evaluated at 0, 1, 2, 3 and 5 days of treatment periods. Fresh weight and dry weight of treated calli were significantly lower in CA03 as compared to the untreated calli. In CA09, the growth of treated calli was significantly lower compared to controls at the later stages of the treatment period. Although decreases in growth were observed for both treated CA03 and CA09, the final reduction in fresh weight at 36% for CA09 compared to its control was much higher compared to CA03 with an 18.2% final reduction in fresh weight. PQ treatment also resulted in a marked decrease in the viability of the callus especially in CA09. Although MDA levels were significantly higher in treated CA03 as compared to treated CA09 at the early treatment stages, they showed a decreasing trend, while MDA levels in CA09 showed an increasing trend, which was significantly higher than that of CA03 at the end of the treatment period. In addition, H2O2 concentrations were generally higher in treated CA09 compared to treated CA03 except at day 3. This study indicated that PQ treatment can induce increases in levels of MDA and H2O2t associated with the decrease in growth and viability of the callus. Results also suggested that CA03 was more tolerant to PQ treatment as compared to CA09.
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