FIGURE 4.

Nitric oxide (NO) production in the root of wild-type and nia30 mutant tobacco at 70 days. (A) NO production, as indicated by green fluorescence detected by DAF-FM staining in roots. The seeds of tobacco bio-primed with T42 were grown under NO₃^- and NH₄⁺ nutrient supplement, and nia30 mutant plants (alone) as well as bio-primed with T42 strain were established in presence of nutrient supplements as described in section “Materials and Methods.” (B) NO production in root expressed as fluorescence intensity (A.U.) related to the same root regions of Figure 5B. NO production and its intensity under the exposure of 100 μM SNP, NO donor, in addition to NO₃^- (C), T42 treatment (D) and NH₄⁺ (E) nutrient with control plants for 48 h in 70 days old plants. Application of NO donor in addition to NH₄⁺ nutrient increased the NO emission in root. The addition of 200 μM cPTIO, NO scavenger reduced fluorescence emission. Values represent the average mean of eleven random selected sites for a definite area from roots (SE; n = 11). Letters on bars indicate significant differences in each treatment at P < 0.05, as determined by Duncan’s test (B–E).