Journal Article

Simultaneous Measurement of Stomatal Conductance, Non-photochemical Quenching, and Photochemical Yield of Photosystem II in Intact Leaves by Thermal and Chlorophyll Fluorescence Imaging

Kenji Omasa and Kotaro Takayama

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 12, pages 1290-1300
Published in print December 2003 | ISSN: 0032-0781
Published online December 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg165
Simultaneous Measurement of Stomatal Conductance, Non-photochemical Quenching, and Photochemical Yield of Photosystem II in Intact Leaves by Thermal and Chlorophyll Fluorescence Imaging

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A new imaging system capable of simultaneously measuring stomatal conductance and fluorescence parameters, non-photochemical quenching (NPQ) and photochemical yield of photosystem II (ΦPSII), in intact leaves under aerobic conditions by both thermal imaging and chlorophyll fluorescence imaging was developed. Changes in distributions of stomatal conductance and fluorescence parameters across Phaseolus vulgaris L. leaves induced by abscisic acid treatment were analyzed. A decrease in stomatal conductance expanded in all directions from the treatment site, then mainly spread along the lateral vein toward the leaf edge, depending on the ABA concentration gradient and the transpiration stream. The relationships between stomatal conductance and fluorescence parameters depended on the actinic light intensity, i.e. NPQ was greater and ΦPSII was lower at high light intensity. The fluorescence parameters did not change, regardless of stomatal closure levels at a photosynthetically active photon flux (PPF) of 270 µmol m–2 s–1; however, they drastically changed at PPF values of 350 and 700 µmol m–2 s–1, when the total stomatal conductance decreased to less than 80 and 200 mmol m–2 s–1, respectively. This study has, for the first time, quantitatively analyzed relationships between spatiotemporal variations in stomatal conductance and fluorescence parameters in intact leaves under aerobic conditions.

Keywords: Keywords: Chlorophyll fluorescence imaging — Non-photochemical quenching — Phaseolus vulgaris L. — Photochemical yield of photosystem II — Stomatal conductance — Thermal imaging.; Abbreviations: ABA, abscisic acid; αp, absorption coefficient of short-wavelength radiation by the leaf; DH, thermal diffusivity in air; DW, water vapor diffusivity in air; ε, emissivity of long-wavelength radiation of the leaf; Es, short-wavelength radiation from the environment; Ew, long-wavelength radiation from the environment; iF, fluorescence intensity image measured under actinic light; iFm, fluorescence intensity image measured during a saturation light pulse during darkness after exposure of the leaf to darkness for at least 1 h; iFm′, fluorescence intensity image measured during a saturation light pulse during steady-state photosynthesis; gaH, boundary layer conductance to heat transfer; gaW, boundary layer conductance to water vapor diffusion; gsl, stomatal conductance to water vapor diffusion of the lower leaf surface; gst, total stomatal conductance to water vapor diffusion; gsu, stomatal conductance to water vapor diffusion of the upper leaf surface; h, relative humidity of air; L, latent heat of evaporation; NPQ, non-photochemical quenching; PAR, photosynthetically active radiation; ΦPSII, photochemical yield of photosystem II; PPF, photosynthetically active photon flux; PSI, photosystem I; PSII, photosystem II; ρcp, volumetric heat capacity of air; σ, Stefan–Boltzmann constant; Ta, air temperature; Tl, leaf temperature; W, transpiration rate.

Journal Article.  8553 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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