Real-time mapping of salt glands on the leaf surface of Cynodon dactylon L. using scanning electrochemical microscopy

Salt glands are specialized organelles present in the leaf tissues of halophytes, which impart salt-tolerance capability to the plant species. These glands are usually identified only by their morphology using conventional staining procedures coupled with optical microscopy. In this work, we have employed scanning electrochemical microscopy to identify the salt glands not only by their morphology but also by their salt excretion behavior. Bermuda grass (Cynodon dactylon L.) species was chosen for the study as they are known to be salt-tolerant and contain salt glands on leaf surfaces. Scanning electrochemical microscopy performed in sodium chloride medium in the presence and absence of potassium ferrocyanide as redox mediator, reveals the identity of salt glands. More insight into the ion expulsion behavior of these glands was obtained by mapping lateral and vertical variations in ion concentrations using surface impedance measurements which indicated five times higher resistance over the salt glands compared to the surrounding tissues and bulk solution. The protocol could be used to understand the developmental processes in plants grown in different soil/water conditions in order to improve salt tolerance of food crops by genetic engineering and hence improve their agricultural productivity.