The effect of cadmium application on the growth, nutrient uptake and steviol glycoside content of stevia (Stevia rebaudiana Bertoni) plant

Cadmium (Cd) is one of the most important heavy metals that causes negativities on plant growth and development. In this study, the effects of Cd treatments (0, 2, 4, 6, and 8 mg kg-1) on growth, nutrient uptake, total phenolics, and steviol glycoside content of stevia (Stevia rebaudiana Bertoni) plants were tested under greenhouse conditions. Herb weights and root dry matter production decreased significantly with increasing Cd treatments. Similarly, Cd treatments decreased plant height, leaf number, leaf and stem weights, total chlorophyll, chlorophyll a, chlorophyll b, chlorophyll a/chlorophyll b ratio, and carotenoid concentrations. The Cd treatments caused a significant decrease in the content of macro and micro elements in the leaves, especially from the dose of 4 mg Cd kg-1. The most significant decrease in related parameters occurred at the level of 8 mg kg-1 Cd. It was observed that stevioside and rebaudioside A levels increased at 2 mg kg-1 Cd dose and started to decrease with increasing Cd doses. Rebaudioside A / stevioside ratio was found to decrease significantly starting from the dose of 4 mg Cd kg-1. Total phenolic compounds and total steviol glycoside contents were found to decrease significantly especially at 8 mg kg-1 Cd level. As a result, it was found that Cd applications negatively affected plant growth and decreased macro- and micronutrient uptake of leaves, while Cd at 2 mg kg-1 dose promoted steviol glycoside production and suppressed glycoside production with increasing Cd application. Key Words : Cadmium, Stevia rebaudiana B., Stevioside, Rebaudioside A, Phenolic compounds