Portal de Periódicos da CAPES

An Automated Dual-Wavelength Spectrophotometer Optimized for Phytochrome Assay

1984; Taylor & Francis; Volume: 13; Issue: 3-4 Linguagem: Inglês

10.1080/10739148408544183

1525-6030

Lee H. Pratt, John E. Wampler, Edwin S. Rich,

Greenhouse Technology and Climate Control

ABSTRACT ABSTRACT A microcomputer-controlled dual-wavelength spectrophotometer suitable for automated phytochrome assay is described. The optomechanical unit provides for sequential irradiation of the sample by the two measuring wavelengths with intervening dark intervals and for actinic irradiation to inter-convert phytochrome between its two forms. Photomultiplier current is amplified, converted to a digital value and transferred into the computer using a custom-designed IEEE-488 bus interface. The microcomputer calculates mathematically both absorbance and absorbance difference values with dynamic correction for photomultiplier dark current. In addition, the computer controls the operating parameters of the spectrophotometer via a separate interface. These parameters include control of the durations of measuring and actinic irradiation intervals and their sequence. Because the data are processed solely within the microcomputer, except for the initial linear amplification, any output desired can be obtained, including automated determination of not only total phytochrome content, but also of the proportions present in the far-red- and red-absorbing forms.