Abstract
We have developed a new image analysis system, capable of quantitative analysis of two aspects of chlorophyll a fluorescence ; i) the changes in intensity of chlorophyll fluorescence during dark-light transitions by the induction method, and ii) the chlorophyll fluorescence quenching by the saturation pulse method. With this system we analyzed the effects of an herbicide on the photosynthetic activity of Phaseolus vulgaris L. leaves. Furthermore, stomatal conductance and assimilation rate were measured with a diffusion porometer.
Results showed that the photosynthetic injuries caused by the herbicide were detected by both fluorescence measurement methods. These injuries were also detected with the porometer as a decrease in stomatal conductance and assimilation rate. Information obtained by the induction method was effective for determining the site in the electron transport system which was damaged by the herbicide. The saturation pulse method could analyze the photosynthetic injuries more quantitatively than the induction method. However, the saturation pulse method required an evenly distributed high level of photosynthetic active radiation (PAR), which makes it difficult to apply to a large leaf area. In contrast, the induction method did not require such a high level of PAR for measurements, and was easier to use for a large leaf area. Consequently, simultaneous use of the saturation pulse method and the induction method enables detailed diagnosis of injuries of the photosynthetic system.
