[Thermoluminescence and electric polarization in chloroplasts]. / Termoliuminestsentsiia i élektricheskaia poliarizatsiia v khloroplastakh.

Exposure of pea chloroplasts to electric field causes the appearance of a new thermoluminescence (TL) band at--(40-50) degrees C and a reduction of the intensity of its main bands. Extents of intensity drop are different for different components of TL and depend on the temperature of illumination. The charge traps responsible for the individual TL components seem to be localized in microsurroundings having different field susceptibility. The electric field effects observable at different temperatures are in correlation with the thermodepolarization currents which reflect the mobility and number of charged groups undergoing a field-induced displacement in chloroplast membranes. Dehydration. of chloroplast film preparations causes a reduction in the intensities of the TL peaks and thermodepolarization currents and a shift of the peaks positions toward higher temperatures. It is assumed that the traps of the recombining charges have two different conformations, each with its own frequency factor for the recombination reaction. Changes in the thermoluminescence behavior in applied electric field are due to the polarization of the traps, which increases the existence probability of a conformation with a high frequency factor.

[Polarization fluorescence of chloroplasts oriented in polyacrylamide gel. Experiment and theoretical analysis]. / Poliarizovannaia fluorestsentsiia khloroplastov, orientirovannykh v poliakrilamidnom gele. Eksperiment i teoreticheskii analiz.

Maize mesophyll chloroplasts were oriented in polyacrylamide gel upon squeezing of gel samples. Fluorescence polarization was measured as a function of the gel deformation parameter. Linearly polarized fluorescence spectra were recorded at -140 degrees. The results show that chloroplasts were oriented in polyacrylamide gel as effectively as in magnetic field. Theoretical models are analyzed for orientation of disc-shaped and rod-shaped chloroplasts. Of these two, only the model for disc-shaped chloroplasts can account for the experimental results. Based on experimental data, the approaches are proposed to estimate the order of alignment of thylakoid membranes within chloroplasts, and to calculate the angles made by transition dipoles with the thylakoid membrane plane. Internal structure of chloroplasts (alignment of thylakoid membranes) is shown to be unchanged upon squeezing of the gel samples.