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Determination of photochemical loss in leaves by an open-ended photothermal cell

1997; Elsevier BV; Volume: 1321; Issue: 2 Linguagem: Inglês

10.1016/s0005-2728(97)00048-0

1879-2650

Mauro Henrique de Paula, Carlos Alberto Vinha, Marco Antonio de Arruda Cortez, Sérgio Placência,

Photoacoustic and Ultrasonic Imaging

The `photochemical loss', here designated by L , of an intact leaf of Nicotiana tabacum was determined both at low and high frequencies of modulation using an open-ended photothermal cell and a conventional photoacoustic cell. The results confirm a previous supposition that this parameter is frequency independent. We can measure L at low frequencies because the open-ended photothermal cell is insensitive to the oxigen evolution. Working at such low frequencies is advantageous because of the better signal-to-noise ratio compared to that of a conventional photoacoustic cell operated at high frequency. The use of the open-ended photothermal cell has an additional advantage due to the fact that measurements can be made with the leaf still attached to the plant.