Chlorophyll Fluorescence as a Probe of the Photosynthetic Competence of Leaves in the Field: A Review of Current Instrumentation

Chlorophyll fluorescence has been widely used in laboratory studies in understanding both the mechanism of photosynthesis itself and the mechanisms by which a range of environmental factors alter photosynthetic capacity. The measurement of chlorophyll fluorescence is both non-destructive and non-invasive, and thus has considerable potential for use in the field situation. Applications range simply from a means of rapidly identifying injury to leaves in the absence of visible symptoms to a detailed analysis of causes of change in photosynthetic capacity. This paper introduces the topic of chlorophyll fluorescence, its interpretation and its application in field studies, giving particular attention to interpretation and measurement of fluorescence induction kinetics and to the application of recently developed modulated light fluorimeters. Three commercial fluorimeters designed for field applications were compared: (1) Plant Stress Meter, BioMonitor AB, Sweden; (2) MFMS, Hansatech Ltd, UK; (3) PAM 101, H. Walz, Federal Republic of Germany. The structure and potential of each are briefly reviewed. It was beyond the scope of this comparison to examine the full potential of each instrument but measurements of the widely used parameter Fv/Fmax were made with each on: (1) Triticum aestivum L. leaves treated with the herbicide Atrazine; and (2) Picea abies (L.) Karst. samples collected from sites which were known to receive different levels of ambient air pollution. In both experiments, the results obtained from the three fluorimeters showed good agreement. The relative merits of each instrument to field applications are discussed. Key-words: Chlorophyll fluorescence, stress detection, fluorimeters, Atrazine treatment, photosynthesis, air pollutants, photosystem II