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Photosynth Res (2008) 96:173179 DOI 10.1007/s11120-008-9292-3
TECHNICAL COMMUNICATION
A new monitoring PAM uorometer (MONI-PAM) to study the short- and long-term acclimation of photosystem IIin eld conditions
Albert Porcar-Castell Erhard Pfndel Janne F. J. Korhonen Eija Juurola
Received: 30 November 2007 / Accepted: 1 February 2008 / Published online: 19 February 2008 Springer Science+Business Media B.V. 2008
Abstract We present and evaluate the performance of a new eld monitoring PAM uorometer (MONI-PAM) which is intended for short- and long-term monitoring of the acclimation of photosystem II (PSII). The instrument measures chlorophyll uorescence, photosynthetic photon ux density (PPFD), and temperature in the eld, and monitors exactly the same leaf area over prolonged periods of time, facilitating the estimation of both rapidly reversible and sustained non-photochemical quenching (NPQ). The MONI-PAM performance is evaluated in the lab and under natural conditions in a Scots pine canopy during spring recovery of photosynthesis. The instrument provides a new tool to study in detail the acclimation of PSII to the environment under natural eld conditions.
Keywords Chlorophyll uorescence Diurnal
acclimation Scots pine Seasonal acclimation AbbreviationsETR Electron transport rateF0 and
Fm
Minimal and maximal chlorophyll uorescence yield from dark-acclimated leavesFt and
F0m
Actual and maximal chlorophyll uorescence yield from light-exposed leavesUP PSII operating efciency
NPQ Non-photochemical quenching
PPFDSL Photosynthetic photon ux density at sample level
PSII Photosystem II
Introduction
Acclimation of photosystem II (PSII) to the light environment is of fundamental importance to adjust the photosynthetic electron ow to the requirements for ATP and NADPH by dark photosynthetic reactions. PSII acclimation involves modulation of the fractions of absorbed light energy that is utilized in photochemistry and that dissipated as heat. Acclimation of PSII takes place on different time scales: short-term adjustments are mostly reversible and occur in the range from minutes to hours in response to, for example, rapidly varying light environments due to temporary shading by clouds or sunecks (Porcar-Castell et al. 2006); long-term acclimation of PSII, however, occurs in response to seasonal light and temperature changes, or to episodes of water, nutrient, or biotic stress (quist and Huner 2003), leading to slowly reversible acclimation in the PSII energy partitioning. Because variations in the energy partitioning in PSII affect the yield of chlorophyll uorescence, measurements of chlorophyll uorescence are widely used to...