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An integrated portable apparatus for the simultaneous field measurement of photosynthetic CO 2 and water vapour exchange, light absorption and chlorophyll fluorescence emission of attached leaves
Author(s) -
IRELAND C. R.,
LONG S. P.,
BAKER N. R.
Publication year - 1989
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1989.tb01975.x
Subject(s) - chlorophyll fluorescence , quantum yield , fluorescence , chemistry , absorption (acoustics) , water vapor , analytical chemistry (journal) , photosynthesis , stomatal conductance , photosynthetically active radiation , materials science , optics , physics , environmental chemistry , biochemistry , organic chemistry
. A portable apparatus has been constructed to measure simultaneously the quantum yield of CO 2 assimilation, light absorption, chlorophyll fluorescence emission and water vapour exchange of attached intact leaves in the field. The core of the instrument is a light‐integrating spherical leaf chamber which includes ports for a light source, photosynthetically active radiation sensor, fluorescence probes and gas inlet and outlet manifolds. Measurement of the quantum flux inside the empty chamber and with a leaf present allows determination of leaf absorptance. An open gas exchange system is employed using an infra‐red analyser to measure leaf CO 2 exchange. Using a DC white light source the quantum yield of CO 2 assimilation based on absorbed light (φ abs ) may be determined rapidly in either ambient air or artificial gas mixtures. Inclusion of capacitance humidity probes into the gas inlet and outlet ports allows simultaneous determination of water vapour exchange and subsequent estimation of stomatal conductance to CO 2 and intercellular CO 2 concentration. Measurement of fluorescence emission by the sample leaf exposed to white light is achieved by a modulated fluorescence detection system. In addition to determination of the minimal, maximal and variable fluorescence levels, a further analysis allows the photochemical and non‐photochemical components of fluorescence quenching, to be estimated. The theory and design of this apparatus is described in detail. The use of the apparatus in the field is demonstrated through a study of the photosynthetic performance of a maize and bean crop during the growing season and by analysis of the photosynthetic performance of crops subjected to nitrogen‐stress and a herbicide treatment.