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A new method to estimate photosynthetic parameters through net assimilation rate−intercellular space CO 2 concentration ( A − C i ) curve and chlorophyll fluorescence measurements
Author(s) -
MoualeuNgangue Dany P.,
Chen TsuWei,
Stützel Hartmut
Publication year - 2017
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.14260
Subject(s) - photosynthesis , photosystem ii , chlorophyll fluorescence , cucumis , carboxylation , chlorophyll a , irradiance , rubisco , analytical chemistry (journal) , absorbance , stomatal conductance , chemistry , respiration rate , conductance , electron transport chain , photosystem i , botany , respiration , biology , physics , environmental chemistry , chromatography , optics , biochemistry , condensed matter physics , catalysis
Summary Gas exchange ( GE ) and chlorophyll fluorescence ( CF ) measurements are widely used to noninvasively study photosynthetic parameters, for example the rates of maximum Rubisco carboxylation ( V cmax ), electron transport rate ( J ), daytime respiration ( R d ) and mesophyll conductance ( g m ). Existing methods for fitting GE data (net assimilation rate−intercellular space CO 2 concentration ( A−C i ) curve) are based on two assumptions: g m is unvaried with CO 2 concentration in the intercellular space ( C i ); and light absorption (α) and the proportion of quanta absorbed by photosystem II (β) are constant in the data set. These may result in significant bias in estimating photosynthetic parameters. To avoid the above‐mentioned hypotheses, we present a new method for fitting A−C i curves and CF data simultaneously. This method was applied to a data set obtained from cucumber ( Cucumis sativus ) leaves of various leaf ages and grown under eight different light conditions. The new method had significantly lower root mean square error and a lower rate of failures compared with previously published methods (6.72% versus 24.1%, respectively) and the effect of light conditions on V cmax and J was better observed. Furthermore, the new method allows the estimation of a new parameter, the fraction of incoming irradiance harvested by photosystem II , and the dependence of g m on C i .