Effects of exogenous nitric oxide on photosynthesis, antioxidative ability, and mineral element contents of perennial ryegrass under copper stress

Abstract

A hydroponics experiment was conducted to test the effects of sodium nitroprusside (SNP, a donor of NO) supplied with different concentrations on copper (Cu) toxicity in ryegrass seedlings (Lolium perenne L.). Excess Cu (200 µM) reduced chlorophyll content, resulting a decrease in photosynthesis. Cu stress induced the production of hydrogen peroxide (H₂O₂) and superoxide anion (O₂^{• −}), leading to malondialdehyde (MDA) accumulation. Furthermore, activities of antioxidant enzymes in Cu-treated seedlings such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were decreased. In addition, Cu stress inhibited the uptake of K, Mg, Fe, and Zn and increased Ca content in roots. Moreover, in leaves of Cu-stressed seedlings, K, Fe, and Zn contents were decreased and the contents of Ca and Mg were not affected significantly. In Cu-treated seedlings, Cu concentration in roots was higher than in leaves. Addition of 50, 100, 200 µM SNP in Cu-mediated solutions increased chlorophyll content and photosynthesis, improved antioxidant enzyme activities, reduced Cu-induced oxidative damages, kept intracellular ion equilibrium under Cu stress, increased Cu concentration in roots and inhibited Cu accumulation in leaves. In particular, addition of 100 µM SNP had the best effect on promoting growth of ryegrass seedlings under Cu stress. However, the application of 400 µM SNP had no obvious alleviating effect on Cu toxicity in ryegrass seedlings.

Keywords:

• antioxidant enzymes
• copper
• Lolium perenne L.
• mineral elements
• oxidative stress

Abbreviations
CAT,	=	catalase;
Cu,	=	copper;
H2O2,	=	hydrogen peroxide;
MDA,	=	malondialdehyde;
NO,	=	nitric oxide;
O2•−,	=	superoxide anion;
POD,	=	peroxidase;
ROS,	=	reactive oxygen species;
SNP,	=	sodium nitroprusside;
SOD,	=	superoxide dismutase.

Abbreviations
CAT,	=	catalase;
Cu,	=	copper;
H2O2,	=	hydrogen peroxide;
MDA,	=	malondialdehyde;
NO,	=	nitric oxide;
O2•−,	=	superoxide anion;
POD,	=	peroxidase;
ROS,	=	reactive oxygen species;
SNP,	=	sodium nitroprusside;
SOD,	=	superoxide dismutase.

Acknowledgments

The authors thank English Lecturer Mr Stuart Craig MA (England, Taishan University of china), and lecturer Xiujuan Wang (College of Foreign Languages, Shandong Agricultural University) for their critical reading and revision of the manuscript. Great thanks were given to Pingping Yang, College of Animal Science Technology, Shandong Agricultural University, China, for her supplying instruments and patient guidance. Special acknowledgments are given to the editors and reviewers.