Figure 1.

NOS activities in the extracts of mock-or TMV-infected tobacco leaves after temperature shift. (A) Xanthi nc (NN) and Xanthi (nn) plants were infected with TMV or buffer (mock) and defense responses were activated by shifting from 32°C to 22°C 48 hr later as described (32). Time is given in hr after shift to 22°C. NOS activity based on arginine to citrulline conversion is plotted against the y axis to the left. NOS activity assayed with the fluorometric method based on nitrite detection is plotted against the right axis. Data represent the mean of three experiments. (B) Inhibition of NOS activity by the NOS inhibitors NMMA and diphenyleneiodonium chloride (250 μM). Data represent the mean of duplicate measurements.