title: In situ measurement of leaf chlorophyll concentration: analysis of the optical/absolute relationship.
abstract: In situ optical meters are widely used to estimate leaf chlorophyll concentration, but non-uniform chlorophyll distribution causes optical measurements to vary widely among species for the same chlorophyll concentration. Over 30 studies have sought to quantify the in situ/in vitro (optical/absolute) relationship, but neither chlorophyll extraction nor measurement 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) implement the most accurate methods to provide equations for conversion of optical to absolute chlorophyll for 22 species grown in multiple environments. Tests of five Minolta (model SPAD-502) and 25 Opti-Sciences (model CCM-200) meters, manufactured from 1992 to 2013, indicate that differences among replicate models are less than 5%. We thus developed equations for converting between units from these meter types. There was no significant effect of environment on the optical/absolute chlorophyll relationship. We derive the theoretical relationship between optical transmission ratios and absolute chlorophyll concentration and show how non-uniform distribution among species causes a variable, non-linear response. These results link in situ optical measurements with in vitro chlorophyll concentration and provide insight to strategies for radiation capture among diverse species.
authors.affiliation: Department of Plants, Soils, and Climate, Utah State University, Logan, UT, 84322, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Parry
authors.forename: J Mark
authors.initials: JM
authors.lastname: Blonquist
authors.forename: Bruce
authors.initials: B
authors.lastname: Bugbee
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D055620:Optical Phenomena; D018515:Plant Leaves / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D013045:Species Specificity
chemical_list: D002734:Chlorophyll
keywords: CCM-200; Chla/Chlb; SPAD-502; leaf optical properties