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The influence of leaf senescence on light dependence of chlorophyll fluorescence of radish leaves

“…To characterize the functional activity of the pho tosynthetic apparatus, the ratio of the fluorescence intensity at the maximum P (F P ) to the steady state fluorescence level F S (F P /F S ) is often used [1,6,[10][11][12][13]. This ChFI parameter is currently widely used in the physiological and ecological studies of plants to determine their tolerance [10,11,13].…”

“…This ChFI parameter is currently widely used in the physiological and ecological studies of plants to determine their tolerance [10,11,13]. It was estab lished that, under long term exposure to a stressor, the F P /F S ratio is changed [1,[11][12][13]. Such a change in the fluorescence parameter is regarded as a criterion of disturbances in the electron transport chain of photo system 2 (PS 2) [1,13].…”

“…Such a change in the fluorescence parameter is regarded as a criterion of disturbances in the electron transport chain of photo system 2 (PS 2) [1,13]. However, it was shown that the F P /F S parameter also decreases in the course of leaf senescence [10][11][12]. It is known that the smallest changes in the F P /F S parameter of the leaf as well as in other important physiological and biochemical parameters of the leaf are observed in the period of maturity (the phase preceding the completion of the leaf growth) [11,13,14].…”

“…However, it was shown that the F P /F S parameter also decreases in the course of leaf senescence [10][11][12]. It is known that the smallest changes in the F P /F S parameter of the leaf as well as in other important physiological and biochemical parameters of the leaf are observed in the period of maturity (the phase preceding the completion of the leaf growth) [11,13,14]. The onset and duration of leaf maturity depend on the species of plants and their cultivation conditions [10,14].…”

“…The onset and duration of leaf maturity depend on the species of plants and their cultivation conditions [10,14]. Fluorescence mea surements are usually performed with leaves at an age of 7-14 days from the date of their appearance [6,[9][10][11]. However, there are difficulties in the unambigu ous interpretation of the state of the photosynthetic apparatus by ChFI parameters under long term expo sure of plants to stressors because of an earlier onset of leaf senescence [11,13].…”