Effect of NaCl on growth and Cd accumulation of halophyte Spartina alterniflora under CdCl2 stress

Abstract

A study quantifying the effect of NaCl on growth and Cd accumulation of Spartina alterniflora subjected to Cd stress was conducted. Seedlings were cultivated in the presence of 1 or 3mM Cd alone, or combined with NaCl (50 or 100mM). The results showed that NaCl magnified the phytotoxicity of moderate Cd stress (1mM Cd) on plants due to reduced levels of plant biomass, plant height, and chlorophyll a+b, while no synergistic effects were recorded under severe Cd stress (3mM Cd). Proline and Ca2+ accumulated along with additional NaCl under moderate Cd stress, instead of reduced or unchanged levels under severe Cd stress owing to different adoption strategies caused by NaCl under different Cd stresses. NaCl reduced the oxidative stress in Cd-treated plants through increasing levels of antioxidative enzymes (catalase (CAT) and peroxidase (POD)) under moderate Cd stress. With NaCl addition, Cd2+ contents in S. alterniflora increased and reduced under moderate and severe Cd stress, respectively. However, total Cd2+ amounts increased with increasing NaCl concentration due to biological dilution. NaCl improved the increase of Cd2+ translocation factor (TF) under moderate Cd stress, indicating that NaCl might improve Cd2+ uptake and translocation from roots to shoots, and enhance the phytoextraction of S. alterniflora on Cd; while phytostabilization of Cd under severe Cd stress may be possible due to the reduced TF. Thus, NaCl alleviated phytotoxicity caused by Cd stress through improved management of osmotic solutes and oxidative status, and affected Cd accumulations in S. alterniflora differently under moderate and severe Cd stresses.