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Related Concept Videos

Atomic Fluorescence Spectroscopy01:29

Atomic Fluorescence Spectroscopy

Atomic fluorescence spectroscopy (AFS) is an analytical technique that involves the electronic transitions of atoms in a flame, furnace, or plasma being excited by electromagnetic (EM) radiation. When these atoms absorb energy, they become excited and subsequently release energy as they return to their original state. This emitted light, or "fluorescence," is observed at a right angle to the incident beam. Both absorption and emission processes transpire at distinct wavelengths, which are...
Super-resolution Fluorescence Microscopy01:37

Super-resolution Fluorescence Microscopy

Super-resolution fluorescence microscopy (SRFM) provides a better resolution than conventional fluorescence microscopy by reducing the point spread function (PSF). PSF is the light intensity distribution from a point that causes it to appear blurred. Due to PSF, each fluorescing point appears bigger than its actual size, and it is the PSF interference of nearby fluorophores that causes the blurred image. Various approaches to achieving higher resolution through SRFM have recently been developed.
Fluorescence and Phosphorescence: Instrumentation01:25

Fluorescence and Phosphorescence: Instrumentation

Fluorometers and spectrofluorometers are two types of instruments used for measuring molecular fluorescence. These instruments differ in how they select excitation and emission wavelengths and the type of light sources they utilize. Fluorometers use absorption interference filters to choose excitation and emission wavelengths. The excitation source in a fluorometer is typically a low-pressure mercury vapor lamp that emits intense lines distributed throughout the ultraviolet and visible regions.

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Related Experiment Video

Updated: Jul 3, 2026

A Small Volume Bioassay to Assess Bacterial/Phytoplankton Co-culture Using WATER-Pulse-Amplitude-Modulated (WATER-PAM) Fluorometry
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A Small Volume Bioassay to Assess Bacterial/Phytoplankton Co-culture Using WATER-Pulse-Amplitude-Modulated (WATER-PAM) Fluorometry

Published on: March 11, 2015

A new minimum fluorescence parameter, as generated using pulse frequency modulation, compared with pulse amplitude

A Harrison Wright1, John M DeLong, Jeffrey L Franklin

  • 1Atlantic Food and Horticulture Research Centre, Agriculture and Agri-Food Canada, Kentville, NS, Canada, B4N 1J5. wrighth@agr.gc.ca

Photosynthesis Research
|August 1, 2008
PubMed
Summary
This summary is machine-generated.

Pulse frequency modulation (PFM) technology

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Area of Science:

  • Plant physiology
  • Photosynthesis research
  • Fluorometry techniques

Background:

  • Pulse amplitude modulation (PAM) fluorometry is a standard method for assessing plant stress.
  • New pulse frequency modulation (PFM) technology offers an alternative approach to measuring fluorescence parameters.
  • Understanding plant responses to environmental stressors like hypoxia and dehydration is crucial for agriculture.

Purpose of the Study:

  • To compare the minimum fluorescence parameter (Falpha) from PFM technology with the minimum fluorescence parameter (Fo) from PAM technology.
  • To evaluate the effectiveness of both methods in detecting reversible low-oxygen stress in apples and irreversible osmotic stress in grapes.
  • To explore the potential of PFM technology for novel fluorescence measurements in plants.

Main Methods:

  • Comparison of Falpha (PFM) and Fo (PAM) under controlled low-oxygen stress in 'Honeycrisp' apples.
  • Assessment of Falpha and Fo under induced osmotic stress (water loss) in 'L'Acadie' and 'Thompson Seedless' grape cultivars.
  • Analysis of fluorescence parameter responses relative to plant physiological changes during stress.

Main Results:

  • Falpha and Fo showed indistinguishable responses to reversible low-oxygen stress in apples.
  • Both parameters similarly responded to the initial stages of irreversible osmotic stress in grapes.
  • Discrepancies emerged in later dehydration stages, with Falpha appearing lower than Fo, potentially due to chloroplast status and measurement artifacts.
  • PFM scans indicated potential for new fluorescence information with biological applications.

Conclusions:

  • PFM technology's Falpha parameter shows promise but requires further investigation, especially concerning its behavior under severe dehydration.
  • Both PFM and PAM fluorometry can detect plant stress, but their direct analogy under all conditions needs careful consideration.
  • PFM technology may offer unique insights into plant physiological responses beyond traditional PAM measurements.