Čajánek M, Navrátil M, Kalina J, Špunda V (1997) Comparison of excitation and emission spectra of chlorophyll a fluorescence at 77K measured with intact barley leaves and leaf homogenates. Acta Facultatis Rerum Naturalium Universitas Ostraviensis, Physica-Chemia 166: 57-66

The excitation and emission spectra of chlorophyll a fluorescence at 77K provide a complex information about structure and function of pigment-protein apparatus of photosystem II and I. The spectra measured on intact leaves reflect the in vivo state of photosynthetic apparatus, however their interpretation is problematical because of several distorting effects such as fluorescence reabsorption, light scattering and reflection within optically heterogeneous system. These distorting effects may be reduced using optically less complicated systems (e.g. leaf homogenates, isolated chloroplasts and/or thylakoid membranes). In these systems the effect of reabsorption is suppressed due to lowered concentration of chlorophyll a and reduced light scattering and reflection on optical inhomogeneities. However, the homogenization and isolation procedures may lead to some disturbance of the structure of pigment-protein complexes and hence to the impairment of their function. Generally, these procedures influence both position and intensity of individual fluorescence bands in emission and excitation spectra. For example the efficiency of transfer of excitation energy is impaired in isolated chloroplasts (Špunda et al.: J. Photochem. Photobiol., in press /1/). In present paper the excitation and emission spectra measured on leaf homogenates and intact barley leaves were compared. The observed changes revealed that the reabsorption was strongly suppressed but similarly as for isolated chloroplast the pronounced impairment of transfer of excitation energy within both photosystems occurred for the leaf homogenate.