pH microelectrode–micropipette system for the measurement of enzyme reactions in a picoliter volume of a living plant cell Original Research Article

A pH microelectrode–micropipette system was found to be feasible for the in vivo detection of an enzyme which was supposed to be generated in a living plant cell in response to stress signals. As demonstrative examples, pH changing enzymes such as luciferase and urease were selected. A solution of luciferase or urease was injected in a leaf cell of Tradescantia virginiana L. with a micropipette, and then its substrate was injected into the same cell. The pH change caused by the enzyme reaction in the picoliter volume of the vacuole was detected with a pH microelectrode. A correlation was obtained between the substrate (luciferin or urea) concentration (5–5000 pM) and the initial changing rate of hydrogen ion concentration.