Low measuring temperature induced artifactual increase in chlorophyll a fluorescence

Area of Science:

• Plant physiology
• Photosynthesis research
• Fluorescence spectroscopy

Background:

• In vivo chlorophyll a fluorescence is crucial for assessing plant stress and photosynthetic efficiency.
• Accurate measurements of photochemical and nonphotochemical quenching are vital for understanding plant responses.
• Low-temperature measurements can introduce experimental artifacts affecting fluorescence parameters.

Purpose of the Study:

• To identify and explain an artifact in chlorophyll a fluorescence measurements at low temperatures.
• To investigate the cause of overestimation in variable fluorescence and underestimation in quenching parameters.
• To provide a method for eradicating this measurement artifact.

Main Methods:

• Measurements of in vivo chlorophyll a fluorescence were conducted at temperatures below 20°C.
• Leaf samples were exposed to actinic light during measurements.
• The role of condensation on fiber-optic probes was investigated.

Main Results:

• Temperatures below 20°C led to artifactual overestimation of variable fluorescence.
• This resulted in negative nonphotochemical quenching and underestimated photochemical quenching values.
• Water vapor condensation on the fiber-optic probe was identified as the cause, distorting the light path.

Conclusions:

• Low temperatures (<20°C) during in vivo chlorophyll fluorescence measurements can cause significant artifacts.
• Condensation on the fiber-optic probe distorts the light path, leading to inaccurate quenching parameter calculations.
• Ensuring the fiber-optic probe remains free of condensation eradicates this artifact, enabling accurate measurements.