Acta Biochimica et Biophysica 10. (1975)
1975 / 1-2. szám - Horváth, I.-Szalay, L.: Photosynthetic Production and Wavelength-dependent Energy Migration
Acta Biochim. et Biophys. Acad. Sei. Hung. Vol. 10 ( 1 — 2), pp. 123—128 (1975) Photosynthetic Production and Wavelength-dependent Energy Migration I. Horváth, L. Szalay Department of Botany and Department of Biophysics, József Attila University, Szeged, Hungary (Received July 4, 1974) If the migration of the excitation energy depends on the wavelength of the exciting light then this can be expected to influence also photosynthetic production in monochromatic light. In the present investigations we started from this assumption. Tomato and paprika seedlings were used in the experiments. Analysis of the results obtained on the two plants does not give a univocal answer to the question of whether the wavelength-dependent energy migration plays an inportant role in the dry-weight increase of the plants. It is beyond doubt, however, that the chlorophyll content and the dry matter increase are affected by the wavelen gth of the light to a considerable degree. Introduction The migration of the electronic excitation energy from some excited molecule to an unexcited neighbouring molecule has been extensively studied since the papers of Förster (1949) and Galanin (1955). Because of its importance in the primary process of photosynthesis, this phenomenon has been repeatedly investigated in the chlorophylls, accounts of the relevant works being given by Hoch and Knox (1968), Losev and Zenkovich (1968), Bennett and Kelley (1968), Knox (1968) and Govindjee and Mohanty (1971). These authors support the Förster energy-migration theory, although the agreement between the theory and the experimental results is not reassuring from a quantitative aspect. It may be assumed that the poor quantitative agreement can be attributed, at least in part, to the fact that, under otherwise identical conditions, the probability of energy transfer depends on the wavelength of the exciting light. Such a dependence was first observed by Weber (1960): in essence, a molecule excited at the edge of the red band of the absorption spectrum was practically unable to transfer the excitation energy to a neighbouring unexcited molecule (red edge effect). Thus, the probability of transfer is different for different excitation frequencies. This is not accounted for by the Förster —Galanin theory. The effect was confirmed by Bauer (1969) in aromatic hydrocarbons, and by Dale and Bauer (1971) in certain other cases. Jablonski (1972) explains the phenomenon in that at an excitation frequency higher than the pure electron transfer frequency, the energy transfer occurs more often during the post-excitation period than in the equilibrium state following vibrational relaxation. Acta Biochimica et Biophysica Academiae Scientiarum Hungaricae 10, 1975