Chlorophyll fluorescence: What is it and what do the numbers mean?

Although results of chlorophyll fluorescence (CF) measurements in nursery seedlings are becoming widely reported in the literature, the theory, terminology, and interpretation of these data are often obscure and confusing to nursery practitioners. This report outlines the underlying physiological basis for chlorophyll fluorometry and discusses measurement protocols and equiment. Interpretations of CF emissions are elucidated using heretofore unpublished data derived from Douglas-fir nursery seedlings.