Influence of nitrate fertilization on Hg uptake and oxidative stress parameters in alfalfa plants cultivated in a Hg-polluted soil

Abstract

The mineral nutrition status of plants might affect the accumulation of heavy metals, which in turn

could be reflected in altered plant sensitivity. Very little information is available about the effect of

the nitrogen nutritional status on mercury (Hg) toxicity. We compared physiological stress parameters

sensitive to Hg in alfalfa (Medicago sativa) plants grown in Hg-polluted soils that were amended with

two different fertilizers: without NO3

− (PK) or with NO3

− (NPK). Several parameters of oxidative stress,

such as antioxidative enzymatic activities, lipid peroxidation, and chlorophyll content were analysed.

The study was carried out in a green house with soil from an agricultural land plot located in Almadén

(Spain), which contained an average Hg concentration of 12.4 mg kg−1, most ofitfound mainly as cinnabar

(HgS). Our results suggest that nitrogen supply prevents oxidative stress in roots, but may improve root

development and increase the uptake of Hg from the soil above safety consumption limits. This work

highlights the importance of proper nitrogen fertilization towards future phytoremediation applications

with alfalfa plants.