Introduction to the USB-PIO: measuring the effect of light on a live leaf – Scanning Probes. Application Note 15Latest updated: May 6, 2020
This application note uses SECM to investigate the effect of switching a blue LED (Light Emitting Diode) on and off on a living plant leaf. To switch the LED the USB-PIO accessory was used. The use of the USB-PIO has allowed the effect of both switching the blue LED over a sequence of experiments and during a Modular Map Experiment, to be investigated.
Shortly after the introduction of SECM its use to investigate plants was demonstrated by Lee et al.  A few years later it was shown that SECM could be used to investigate living plants . Since these works SECM has been used in a number of investigations of plants , proving particularly useful in the investigation of plant stomatal activity [2-4]. The plant stomata, Fig. 1, help regulate the ingress of CO2 for photosynthesis, and the loss of the O2 and H2O by-products. One of the many factors affecting the opening and closing of the stomata is light and its intensity. The stomata themselves are opened and closed by the surrounding guard cells. When the stomata are open the guard cells are turgid and have a higher topography than the surrounding area, they relax on stomata closing and their topography is lower than in the turgid state . This means that when using SECM to investigate the effect of light on a live plant leaf two different effects can be detected: (1) A change in current due to changing O2 concentration. (2) A change in current due to the changing topography around the stomata.
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