Enhanced in vitro regeneration and change in photosynthetic pigments, biomass and proline content in Withania somnifera L. (Dunal) induced by copper and zinc ions

In the present study the effect of inorganic nutrients (CuSO4 & ZnSO4) on morphogenic and biochemical responses from nodal explants in Withania somnifera L. was investigated. Incorporation of either Copper sulphate (25–200 μM) or Zinc sulphate (50–500 μM) in the optimized Murashige and Skoog (MS) medium highly influenced the shoot bud formation and subsequent elongation, which induced maximum percentage (95%) regeneration, number (61.7 ± 0.25) of shoots with shoot length (5.46 ± 0.16 cm) on CuSO4 (100 μM) and maximum percentage regeneration (100%), number of shoots (66.1 ± 0.96) with shoot length (6.24 ± 0.21 cm) on ZnSO4 (300 μM) after 12 weeks of culture. Healthy growing in vitro microshoots rooted efficiently on ½ MS medium supplemented with NAA (0.5 μM), which induced (16.2 ± 0.12) roots with root length (3.30 ± 0.12 cm) after 4 weeks. Pigment content increased with increasing concentration of Cu and Zn and the maximum Chl. a (0.47), (0.41); Chl. b (0.52), (0.42); total Chl. (0.99), (0.83) and Carotenoid (0.16), (0.16) mg/g FW contents in regenerants were found on CuSO4 (100 μM) and ZnSO4 (300 μM), respectively. Maximum proline content (0.17), (0.16) μg/g FW was observed on high concentrations of CuSO4 (200 μM) and ZnSO4 (500 μM) respectively, in the basal medium. Regenerated plantlets were acclimatized successfully in soilrite with a survival rate of 95%. No morphological variations were detected among the micropropagated plants when compared with seedling raised plants of the same age.

► Effect of toxic metals (CuSO4 and ZnSO4) was evaluated in Withania somnifera.
► MS + BA + NAA + Cu + Zn induced maximum percentage of shoot regeneration.
► Pigment content & biomass level increased on high concentration of metals.
► Proline concentration showed maximum content at 200 μM (Cu) & 500 μM (Zn).
► Proline accumulation was observed in the plant under stress.