Biophysically-Based Measurement of Plant Water Status Using Canopy Temperature
نویسندگان
چکیده
In situ optical meters are widely used to estimate leaf chlorophyll concentration, but non-uniform chlorophyll distribution causes the opticalmeasurement to vary widely among species for the same chlorophyllconcentration. Over 30 studies have sought to quantify the in situ/in vitro (optical/absolute) relationship, but neither chlorophyll extraction normeasurement techniques for in vitro analysis have been consistent among studies. Here we: 1) review standard procedures for measurement of chlorophyll,2) estimate the error associated with non-standard procedures, and 3) implementthe most accurate methods to provide equations for conversion of optical toabsolute chlorophyll for 22 species grown in multiple environments. Tests of fiveMinolta (model SPAD-502) and 25 Opti-Sciences (model CCM-200) meters, manufactured from 1992 to 2013, indicate that differences among replicatemodels are less than 5 %. We thus developed equations for converting betweenunits from these meter types. There was no significant effect of environment onthe optical/absolute chlorophyll relationship. We derive the theoreticalrelationship between optical transmission ratios and absolute chlorophyllconcentration and show how non-uniform distribution among species causes avariable, non-linear response. These results more rigorously link in situ opticalmeasurements with in vitro chlorophyll concentration and provide insight to strategies for single-leaf radiation capture among diverse species.
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