NEW PORTABLE PHOTOACOUSTIC AND FLUORESCENCE PHOTOMETER FOR FIELD MEASUREMENT OF PHOTOSYNTHESIS

A new portable photoacoustic and fluorescence photometer has been buil t. The instrument is especially made for field measurements but can al so be used indoors. This new instrument has many advantages. It can me asure the photosynthetic O2 evolution and energy storage, and the vita lity index in the same sample. The system is very compact, which makes it easy to transport. A small electrical generator satisfies the 110 V power requirement for field applications. All manipulations are comp uter controlled including the data acquisition and treatment. The phot oacoustic signal-to-noise ratio for carbon black is the same under fie ld conditions as in the laboratory (approximately 2 X 10(4)) at 130 Hz . Results obtained on declining sugar maple trees in the field are pre sented. The combination of photoacoustic and fluorescence measurements in one instrument represents a very powerful tool in photosynthesis r esearch.