The fluorescence pulse method as a tool to characterize the photosynthetic system of plants and algae

In order to obtain useful information in a reduced time spent, the method of chlorophyll fluorescence induction kinetics has been modified. An excitation pulse of rectangular shape with a power density P (0.1 mW/cm²-70 mW/cm²) and a pulse width T (T=0.55-2 ms) is used to induce the fluorescence of dark adapted plants. Its initial value F_o is the ground fluorescence. The further increase of the fluorescence intensity F(t) during the excitation pulse can be described by F_al·(1-exp(-t/T_al)). F _o, F_al and T_al depend on e.g. the chlorophyll content, the herbicide concentration, water stress and P. Measurements show that a dark adaptation of 0.2 s is sufficient and that results can also be obtained even without any dark adaptation. The distance between measuring device and object can be varied between 0.5 m and 3 m