SEASONAL-CHANGES OF CHLOROPHYLL FLUORESCENCE IN NEEDLES OF SCOTCH PINE

We investigated seasonal and age changes in induction of millisecond d elayed fluorescense (DF) of chlorophyll and the temperature dependenci es (thermograms) obtained for amplitudes of the steady-state level of DF and zero level of chlorophyll fluorescence (F0) in needles of Scotc h pine (Pinus sylvestris L.) growing under conditions of the middle Ur als. The thermograms of F0 showed two components observed at 44-64-deg rees-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 yi eld occurs in February-March. The temperature dependency of DF in the range of 2-54-degrees-C contains a number of components, whose amplitu de depends on the season, increasing toward the onset of winter. Compl ete 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 chara cteristic of young needles in the growth phase. The multiphasic nature of DF induction curves can be removed by means of temperature reducti on to 10-degrees-C or by two-step increase in the intensity of excitin g light.