Fluorescence decline ratio: Comparison with quantum yield ratio for plant physiological status and herbicide treatment responses

Abstract

Plant fluorescence is normally measured using the ratio Fv/Fm (quantum yield). An alternative measurement, fluorescence decline ratio (Rfd), can be used instead of Fv/Fm. The usefulness of the Rfd ratio in comparison to Fv/Fm was tested with three plant species of differing leaf character. Diurnal trends were measured after treatment with two herbicides, diuron, a lipophilic photosynthesis inhibiting herbicide and dalapon, a less-lipophilic non-photosynthesis inhibiting herbicide. In wheat, both herbicides were tested with three non-ionic surfactants of differing hydrophile-lipophile balance (HLB). The Rfd ratio was a more sensitive numerical indicator of plant responses and provides an alternative approach to monitoring and measuring the effect of stress factors in plants.