Effect of 15 days iso-osmotic (0.70 MPa), NaCl (150 mM), or PEG-8000 (20% w/v) stress on oxidative damage in sugarcane plants. Different letters in each column indicate significant differences at P50.05, according to Least Significant Difference (LSD) test. Standard error of the three treatment means, SE (M) and LSD values for each parameter are given in the last row.