Ammonium Alleviates Redox State in Solanum Seedlings under Cadmium Stress Conditions

Afef Nasraoui -Hajaji,Houda Gouia,Elisa Carrayol Carrayol

doi:10.4172/2161-0525.1000141

Afef Nasraoui -Hajaji, Houda Gouia + Show 1 more

Open Access

https://doi.org/10.4172/2161-0525.1000141

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Abstract

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.

Highlights

Cadmium (Cd) is one of the most important metals in terms of food-chain contamination, because it is readily taken up by the cells of different plant species [1,2]
Results shown in figure 1D demonstrated that cadmium was less accumulated in leaves of tomato grown with ammonium than with nitrate
There is evidence suggesting that tomato plants are partially protected against Cd when received ammonium as nitrogen source

Summary

Introduction

Cadmium (Cd) is one of the most important metals in terms of food-chain contamination, because it is readily taken up by the cells of different plant species [1,2]. Plants face constant risk from reactive oxygen species (ROS), which are inevitably generated as products of photosynthesis and other cellular metabolic processes [8]. ROS are produced continuously as byproducts of various metabolic pathways that are localized in different cellular compartments [9], but under stressful conditions, their formation might be in excess of antioxidant scavenging capacity, creating oxidative stress by reaction and damage to all biomolecules, especially proteins, due to the higher rate constants of the reaction of the superoxide anion with amino acid side chains [10]. Plants need to earnestly control ROS overall levels by the co-ordinated action of several antioxidant enzymes such as superoxide dismutase (SOD, E.C. 1.15.1.1), catalase (CAT, E.C. 1.11.1.6), ascorbate peroxidase (APX, E.C. 1.11.1.11), and glutathione reductase (GR; EC 1.6.4.2). Excessive ammonium uptake into plants can lead to toxic effects [5,14]

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