Fig. 4.

ROS and ONOO⁻ accumulation in root apices of rice seedlings treated with NO donor (SNP) and either receiving non-water stress (Con) or subjected to water stress using PEG. After 3 h, O₂^.- (a), H₂O₂ (b), and OH⁻ (c) levels in rice seedlings roots were measured by spectrophotometry. ONOO^- production expressed as relative fluorescence (d). The accumulation of ONOO^- was detected with 10 μΜ aminophenyl fluorescein (e), Bar =3 00 μm. Fluorescence images and relative fluorescence intensity were analyzed as described in Fig. 2 for NO determination. Values represent means ± standard error (SE) (n = 6). Different letters indicate significant differences at P < 0.05. Con indicates control treatment for each N nutrition, i.e., plants receiving non-water stress. FW: fresh weight