Adding sodium nitroprusside and EDTA to strengthen cadmium tolerance and cadmium accumulation of ryegrass

Objectives Ryegrass is an effective bioremediation plant of Cadmium (Cd) contamination soil. The effects of exogenous sodium nitroprusside (SNP) and EDTA were tested to increase the Cd tolerance and accumulation of ryegrass. In order to clarify the effect and mechanism of exogenous SNP and EDTA in strengthening ryegrass remediation of soil Cd contamination.

Methods Hydroponic culture method was used with the Hoagland nutrition solution as base, the effects of the application of exogenous SNP and EDTA on growth, physiological characteristics and cadmium accumulation of ryegrass under the stress of 100 μmol/L Cd were studied with ryegrass (Lolium perenne L.) as the experimental material, sodium nitroprusside (SNP) as the donor of nitric oxide (NO) and EDTA as the regulatory substance. There were eight treatments, CK, Cd, EDTA, SNP, Cd + EDTA, Cd + SNP, EDTA + SNP and Cd + EDTA + SNP. The effects of SNP and EDTA on cadmium content, growth index, root activity, photosynthetic pigment content, \rmO_\small 2^\overline \,\cdot\, generation rate, H₂O₂ content, malondialdehyde content, electrolyte leakage and antioxidant enzyme activity of ryegrass under the cadmium stress were studied.

Results Under non-stress conditions, exogenous addition of EDTA and SNP significantly reduced the plant height, root length and root activity of ryegrass, and significantly increased the \rmO_\small 2^\overline \,\cdot\, generation rate, H₂O₂ and MDA content in the above-ground and underground parts of ryegrass. The Cd stress significantly inhibited the growth of ryegrass. The addition of SNP and EDTA could alleviate the damage and their combined treatment had better effect. Compared with the Cd control, the shoot height and root length of the Cd + EDTA + SNP treatment were increased by 68.8% and 59.6%, and the fresh and dry weight were increased by 62.6% and 60.0% respectively. The SOD activities of shoots and roots were increased by 32.5% and 67.6%, the POD activities were increased by 49.8% and 67.6%, the APX enzyme activities were increased by 134% and 102%, the MDA contents were decreased by 30.4% and 21.8%, and the \rmO_\small 2^\overline \,\cdot\, generation rates were decreased by 29.0% and 26.1%, respectively. At the same time, the contents of cadmium in shoots and roots were increased by 89.7% and 30.2%, respectively, and the difference was significant.

Conclusions The addition of 100 μmol/L SNP, 0.5 mmol/L EDTA, 0.25 mmol/L EDTA and 50 μmol/L SNP has inhibitory effects on the growth of ryegrass under non-stress. The addition of both SNP and EDTA can promote the uptake and accumulation of Cd in the aboveground parts of ryegrass, enhance its tolerance to Cd and effectively alleviate the inhibiting effect of Cd stress on ryegrass growth. The simultaneous application of EDTA and sodium nitroprusside is proved of more efficient than the individual does, as a result, is recommended in the practical use.