Nitrogen and carbon contents, nitrogen use efficiency, and antioxidant responses of perennial ryegrass accessions to nitrogen deficiency

The study was designed to investigate nitrogen and carbon contents, nitrogen use efficiency, and antioxidants of a tolerant accession PI231578 (TOL) and a susceptible PI306292 (SUS) of perennial ryegrass subjected to 7.5 mM N (control) and 0.75 mM N (low) for 6, 12, and 20 d in a growth chamber. The SUS had decreased plant height, dry matter, shoot carbon content and showed more reductions in leaf chlorophyll and shoot N content at 6, 12 d or 20 d of low N. An increased N use efficiency was greater in the shoots of SUS during the low N treatments and in the roots of TOL at 20 d. Shoot soluble protein content (TSP) was unaffected in TOL but decreased in SUS at 20 d of low N, whereas shoot catalase activity decreased in SUS. Root superoxide dismutase and peroxidase activities increased in TOL at 20 d of low N.