Fig. 2. Effect of darkness on net NO^-₃ uptake, at 20 and 30°C, by Pima (A) and Acala (B) cotton seedlings grown in 0.1 mM NO^-₃ at 30/20°C light/dark temperatures. The seedlings at the end of the light cycle were transferred into the uptake solutions and placed in the dark for the measurement of uptake rates at 20°C (circles) or 30°C (triangles). Open and closed symbols represent measurements from different sets of plants during the time course