STOMATAL RESPONSES MEASURED USING A VISCOUS-FLOW (LIQUID) POROMETER

The design of a liquid flow porometer for the measurement of stomatal responses in epidermal peels is described. The system is computerized and allows automatic measurement of about 1000 stomata (of Commelina communis L.) in three parallel experiments. Simultaneous microscopic observations of the stomata is also possible. Conditions are described for rapid measurement of stomatal responses with greater resolution than that achieved by conventional microscopic measurement techniques. To determine which feature(s) of the stomatal pore influenced the flow rate the most precise estimates of pore diameter and area were made using a cryo-fixation technique, scanning electron microscopy and image analysis. Flow rate showed a near linear dependence on pore area. The LFP was evaluated for measuring stomatal responses by comparison with conventional Petri-dish experiments. Responses to KCl, CO2, fusicoccin, and ABA were similar using the two methods, though there was little or no response to light in the LFP. Pore widths were also lower in the LFP under similar experimental conditions. The probable causes of these phenomena are discussed.