Abstract
We present a simple procedure for measuring the pH in the apoplast of the rice root, using the fluorescent ratio method and Oregon Green 488 (OG). Staining with 5 μM OG for 3 min followed by 5-min washing with calcium solution was an effective method for measuring the pH of the apoplast at the root surface. In order to prevent the diffusion of OG from the apoplast, the circulation of a low concentration of OG (0.02 μM) in a root vessel was found to be a useful modality. However, aluminum ion disturbed pH measure-ment. In the presence of 50 μM AlCl3, the pH value was inaccurate at the pH rage higher than pH 5.0.
