PARENT SESSION
Posters P2B Light, redox and metabolic regulation: Light Reactions. Abstracts (444-478)

Statistical properties of parameters evaluated from the O-J-I-P chlorophyll a fluorescence transients and their changes upon high temperature stress. Dušan Lazár^*,1, Petr Sušila¹, Jan Nauš¹, ¹ Laboratory of Biophysics, Olomouc, Czech Republic

ABSTRACT- The O-J-I-P chlorophyll a fluorescence rise, though not fully understood nowadays, is very often used in photosynthesis research because its measurement is cheap, easy performed, and not destructive. One way to understand the origin of the O-J-I-P transient and its changes upon stress action is to study statistics of parameters evaluated from the transients when measured many times. In this work we focused on effect of high temperature (23 - 65 ^oC) on statistical properties of the parameters (F₀, F_M, F_V/F_M, etc.) by measurements of the transients (N = 120 for each temperature) with whole barley leaves. We found that shapes of histograms of the fluorescence parameters evaluated from the transients were changed upon high temperature stress: in some cases, more precisely, the histogram was skewed to one side upon control conditions then it was symmetrical and finally it was skewed to the other side when temperature increased. Different variances of the fluorescence parameters evaluated from the transients were also found and the increased temperature caused an increase in the variances. As difference in the variances of the fluorescence parameters can be indicative of different processes described by the parameters, a mutual independence of two fluorescence parameters can be evaluated on the basis of their variances. We found that the independence of the fluorescence parameters is changed upon high temperature stress: the independence raised and then decreased when temperature increased but opposite behavior was also found. We discuss the observed statistical properties of fluorescence parameters with respect to physical nature of fluorescence signal and physiological meaning of the fluorescence parameters.

KEY WORDS: chlorophyll fluorescence, statistics, barley, high temperature