Role of polyamine in combating heavy metal stress in Stevia rebaudiana Bertoni under in vitro conditions.

Environmental stress severely restricts the distribution and productivity of plants. Heavy metal is one of the major abiotic factors which can limit crop productivity, especially in arid and semi arid region. Cadmium (Cd) is of particular concern to human health as it can be readily absorbed by roots and concentrated in many cereals, potatoes, vegetables and fruits. Elevated levels of Cd generally inhibit seed germination, cell growth as well as whole plant growth, nutrient uptake, distribution and photosynthesis. The purpose of present study was to evaluate the performance of medicinally important Stevia plants exposed to cadmium stress under in vitro culture conditions, and further to investigate the mitigating effect of polyamine (putrescine) on Cd stress in terms of morphological responses. Half-strength Murashige and Skoog (MS) media was used. The data showed significant decline in shoot length, number of leaves, leaf length and other morphological attributes in Stevia leaves with increasing concentration of cadmium salt, and that exogenous application of putrescine in the culture reversed the Cd induced effects.