SEASONAL-CHANGES OF CHLOROPHYLL FLUORESCENCE IN NEEDLES OF SCOTCH PINE

We investigated seasonal and age changes in induction of millisecond delayed fluorescense (DF) of chlorophyll and the temperature dependencies (thermograms) obtained for amplitudes of the steady-state level of DF and zero level of chlorophyll fluorescence (F0) in needles of Scotch pine (Pinus sylvestris L.) growing under conditions of the middle Urals. The thermograms of F0 showed two components observed at 44-64-degrees-C during the period of active vegetation and a component at 64-74-degrees-C arising in the winter. The greatest decline of DF and F0 yield occurs in February-March. The temperature dependency of DF in the range of 2-54-degrees-C contains a number of components, whose amplitude depends on the season, increasing toward the onset of winter. Complete suppression of DF is observed at 54-degrees-C. The fall and spring transitional periods are characterized by the presence of additional maxima and bends on the curve of DF induction. The same thing is characteristic of young needles in the growth phase. The multiphasic nature of DF induction curves can be removed by means of temperature reduction to 10-degrees-C or by two-step increase in the intensity of exciting light.