Toxicologie environnementale et analytique

Ammonium Alleviates Redox State in Solanum Seedlings under Cadmium Stress Conditions

Abstract

Afef Nasraoui-Hajaji*,Houda Gouia,Elisa Carrayol,Chiraz Haouari-Chaffei

Cadmium effects on growth and oxidative stress were investigated in 21-day-old tomato seedlings (Solanum) grown in hydroponics media containing 5 mM of KNO3 or (NH4)2SO4 and three Cd levels as CdCl2 (0, 5 and 25 μM) for 14 d. Cadmium was more accumulated in nitrate-fed tomato compared to ammonium-fed ones. Dry weight, Chla, Chlb and carotenoides contents were reduced in NO3--fed tomato. But in NH4 +-fed plants the parameters were increased. Cadmium induced an increase in the H2O2 and MDA levels which was more pronounced in nitrate-fed tomato. Antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase(APX) were induced with Cd. But, the enhancement degree of these enzymes activities were higher in ammonium-fed tomato compared to those grown with nitrate. These data suggested that antioxidative activity developed by tomato leaves is more induced by cadmium when ammonium was added in nutrient solution as nitrogen source. This can be related to the ability of cadmium to induce an accumulation of reactive oxygen species (ROS) less pronounced in presence of ammonium regime. The beneficial effect of NH4+ on Cd toxicity was confirmed by a significant decrease in MDA level and accumulation of photosynthetic pigments.