Fig. 4.

Effects of incubate with SNP, IAA and tungstate for 48 h on endogenous NO levels in primary root apices of maize plants grown in low- (0·01 mm) or high- (10 mm) nitrate solution for 7 d. The NO-specific fluorescent dye DAF-2DA was loaded into roots and fluorescence was detected by a confocal microscopy. Representative images are shown, and scale bars = 500 µm. (A–D) are roots grown in low nitrate (0.01 mM) without any other treatment (A), (B–D) are roots grown in low nitrate and treated with 1 µM SNP (B), 100 nM IAA (C) and 100 µM tungstate (D); (E–F) are roots grown in high nitrate (10 mM) without other treatment (E) and treated with 1 µM SNP (F), 100 nM IAA (G) and 100 µM tungstate (H), respectively. The graph below shows mean fluorescence intensities in the root apices expressed as pixel numbers relative to those measured in 0·01 mm nitrate (G). Data are means ± s.e. from measurements of at least six roots for each treatment. Different letters indicate significantly different values (P = 0·05).