Light Production by Green Plants

Abstract

The present communication offers evidence which suggests that the photosynthetic reactions are at least slightly reversible, inasmuch as plants which have been irradiated give off fight for a considerable period of time after illumination. It also seems likely that this reaction is quite distinct from fluorescence or simple phosphorescence in its behavior.The phenomenon here described was uncovered in an attempt to demonstrate the formation of energy-rich phosphorus during photosynthesis using the firefly luminescent system as an indicator of ATP formation (1). A mixture of chloroplasts and purified firefly extract gave appreciable light following illumination. However, the chloroplasts were found to be capable of doing this in the absence of the firefly extract, thereby ruling out, at the present, any conclusions as to phosphate intervention. Materials and MethodsThe light was measured with a 1P21 photomultiplier followed by two stages of amplification feeding into a Brown recorder. In order to give constant Brown recorder readings a circulating system was used. (See Fig. 1.) Chlorella, Scenedesmus, and Stickococcus were grown in Knop's solution at 20°C., aerated with 5 per cent CO2, and illuminated with fluorescent tubes. Characteristics of Chlorella LuminescenceThe simple experiment of starting the pump in the circulating system ( Fig. 1) at various times after the exciting light had been turned off was sufficient to show that fight was emitted at room temperature for as long as 30 seconds after illumination. Light production could be demonstrated for as long as 2 minutes after illumination when quanta were counted with the photomultipfier at liquid nitrogen temperatures. The decay curves shown in Fig. 2 were obtained by replacing the Brown with a Brush recorder (which has a fiat frequency response from D. C. to 100 cycles per second). In these curves the zero values have been set equal to 1 although in the 28°C. experiment much more fight was emitted (see Fig. 6). It will be seen that the temperature has a profound effect on the shape of the curve. A good fit is obtained for a bimolecular reaction at 6.5°C.

A Distorted Circadian Clock Causes Early Flowering and Temperature-Dependent Variation in Spike Development in the Eps-3Am Mutant of Einkorn Wheat

“…The DF phenomenon, discovered by Strehler and Arnold (1951) is a luminescence produced by the photosynthetic apparatus after excitation with ambient light as a result of charge recombination in the photosystem II (PSII) and subsequent emission of a photon (Rutherford et al 1984). DF allows measuring the intrinsic oscillation in chlorophyll fluorescence (PSII) that remains under circadian control (Gould et al 2009).…”

Govindjee at 80: more than 50 years of free energy for photosynthesis

“…Understanding of the mechanism of thermoluminescence and delayed light emission in photosynthetic systems: beyond William Arnold Govindjee is known for his insight into the mechanism of delayed light emission (or delayed fluorescence) and thermoluminescence. William Arnold, a former student of Robert Emerson, had not only discovered, in 1932, the concept of the ''Photosynthetic Unit'' with Emerson, but, in 1951, with Bernard Strehler, he discovered delayed light emission, while investigating the possible synthesis of ATP by plants (Strehler and Arnold 1951), and later, in 1957, he discovered the phenomenon of thermoluminescence (afterglow) with Helen Sherwood (Arnold and Sherwood 1957). Mar and Govindjee (1971) discovered that preilluminated spinach chloroplasts and Chlorella pyrenoidosa, when given a quick temperature jump of about 15°C, emitted light.…”

A Survey of Epr Investigations of Bacterial Photosynthesis

“…Although suggestions were advanced many years ago that chlorophyll triplet states might be involved in photosynthesis (Strehler and Arnold, 1951 ;Fujimor, and Livingston, 1957) most investigators assumed, primarily because of lack of evidence to the contrary, that the primary quantum conversion reaction occurred via the excited singlet states of the pigments in the reaction center (see Clayton, 1972, for example). However, this assumption must be reconsidered in light of the recent observation of triplet EPR signals in Chromatium D sub-cellular preparations by Dutton et ul.…”