Abstract
Measurements of photosynthetic processes in hydrophytes mostly involve photosynthometers, which capture the escaping gas for subsequent analysis The most common method to detect changes in the rate of photosynthetic processes is to count the series of escaping gas bubbles. The emerging bubbles are either simply counted or they are recorded using light barriers, which is very difficult because of their small size and often varying ascent rate. The gas bubbles generated during photosynthesis by aquatic plants produce distinctive sound pulses when leaving the plants. These acoustic side effects enable completely new and highly accurate measurements. The frequency and reaction time changes of the pulses caused by external influences are therefore accurately detectable. The precise time measurements enable registering and evaluating the curves as reactions to changes in physical or chemical environmental conditions. We show that such acoustic analyses open completely new research opportunities for plant physiology.
Highlights
These counting methods are cumbersome, uncertain and inaccurate
The type of bubble formation can be divided into three categories: 1. Irregular bubble emission: the time sequence of bubbles reveals no regularity
The periodicity of the frequency changes of the waves is accurate as the regular series
Summary
Exact curves at changes in photosynthesis intensity cannot be determined because it is not possible to determine the time intervals from pulse to pulse: only the number of pulses within larger time intervals can be recorded. Our many years of work with aquatic organisms as well as through the use of video recordings showed that the typical sound pulses during photosynthesis are not caused by the passage of the bubbles through the water surface, but upon emergence from the stomata. The same effects occur when air bubbles emerge from damaged plant tissue. This provides the opportunity to establish the exact time of bubble emission. This phenomenon proved to be the basis for exact acoustic measurements, opening entirely new possibilities for plant physiology
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