Figure 8. Nitric oxide (NO) was involved in oxytetracycline (OTC)-induced decline in H₂O₂ levels and arrest of the cell cycle in tomato root tips.

(a,b) Effects of 250 μM cPTIO, scavenger of NO on H₂O₂ levels and expression of cell cycle genes in tomato root tips in the presence or absence of 10 μM oxytetracycline (OTC). H₂O₂ was visualized by staining with DAB (a) or H₂DCF-DA (b). The fluorescence intensity for H₂O₂ accumulation in the root tips is shown in each image. Measurements were taken 24 h after treatments, and data are the means of 3 replicates with SE. Means followed by the same letter are not significantly different according to Tukey’s test (P < 0.05). The bar indicates 120 μm. (c,d) Effects of 250 μM cPTIO and 1 mM H₂O₂ on the expression of cyclin genes (CYCA3;2, CYCD3;3, CYCB1;1, CYCB1;2, CYCD3;1) and CDKB2;1 gene (encoding cyclin-dependent kinase B2;1) in tomato root tips in the presence or absence of OTC. Samples were collected 24 h after treatment.