Figure 2. Nitric oxide (NO) synthesis in ABA inhibition of stomatal opening. (a) Epidermal strips were loaded with 10 µM DAF2-DA for 15 min. After treatment with 0 µM of ABA, 10 µM of ABA or 10 µM of ABA + 100 µM cPTIO for 30 min, they were observed using an epifluorescence microscope. Data are shown as a ratio of blank (0 µM ABA ) and treatment. Bars represent standard errors of means. (b,c) Images depicting NO synthesis induced by ABA treatment. (b) 0 µM ABA. (c) 10 µM ABA.