scholarly journals THE IDENTITY OF THE FLUORESCENT AND DELAYED LIGHT EMISSION SPECTRA IN CHLORELLA

1954 ◽  
Vol 37 (5) ◽  
pp. 677-684 ◽  
Author(s):  
William Arnold ◽  
J. B. Davidson
Keyword(s):  
Emission Spectrum ◽  
Light Emission ◽  
Wave Length ◽  
Emission Spectra ◽  
Chlorella Pyrenoidosa ◽  
Fluorescent Light ◽  
Low Light ◽  
Delayed Light Emission ◽  
Light Intensities ◽  
Length Range

1. The delayed light emission of Chlorella pyrenoidosa over the wave length range 400 to 950 mµ has been investigated. 2. Emission of delayed light is confined to the range 600 to 800 mµ. 3. To the precision with which the low light intensities involved can be measured with the apparatus in these experiments, the emission spectrum of the delayed light is the same as the spectrum of the fluorescent light. 4. Thus the delayed light must come from excited chlorophyll.

scholarly journals LIGHT PRODUCTION BY GREEN PLANTS

1951 ◽  
Vol 34 (6) ◽  
pp. 809-820 ◽  
Author(s):  
Bernard L. Strehler ◽  
William Arnold
Keyword(s):  
Light Emission ◽  
Reaction Order ◽  
Wave Length ◽  
Action Spectrum ◽  
Fluorescent Light ◽  
Exciting Light ◽  
Enzymatic Reactions ◽  
Green Plants ◽  
Light Production ◽  
Two Temperature

1. Green plants have been found to emit light of approximately the same color as their fluorescent light for several minutes following illumination. This light is about 10–3 the intensity of the fluorescent light, about one-tenth second after illumination below saturation or 10–6 of the intensity of the absorbed light. 2. The decay curve follows bimolecular kinetics at 6.5°C. and reaction order 1.6 at 28°C. 3. This light saturates as does photosynthesis at higher light intensities and in about the same intensity range as does photosynthesis. 4. An action spectrum for light emitted as a function of the wave length of exciting light has been determined. It parallels closely the photosynthetic action spectrum. 5. The intensity of light emission was studied as a function of temperature and found to be optimal at about 37°C. with an activation energy of approximately 19,500 calories. Two-temperature studies indicated that the energy may be trapped in the cold, but that temperatures characteristic for enzymatic reactions are necessary for light production. 6. Illumination after varying dark periods showed initial peaks of varying height depending on the preceding dark period. 7. 5 per cent CO2 reversibly depresses the amount of light emitted by about 30 per cent. About 3 minutes are required for this effect to reach completion at room temperatures. 8. Various inhibitors of photosynthesis were tested for their effect on luminescence and were all inhibitory at appropriate concentrations. 9. Irradiation with ultraviolet light (2537A) inhibits light production at about the same rate as it inhibits photosynthesis. 10. This evidence suggests that early and perhaps later chemical reactions in photosynthesis may be partially reversible.

A laboratory study of vertical migration

1955 ◽  
Vol 144 (916) ◽  
pp. 329-354 ◽  
Keyword(s):  
Light Intensity ◽  
Vertical Migration ◽  
Time Course ◽  
Tap Water ◽  
Low Light ◽  
Overhead Light ◽  
Light Intensities ◽  
Orientation Response ◽  
Reduced Light ◽  
Characteristic Maximum

In a tank filled with a suspension of indian ink in tap water, a population of Daphnia magna will undergo a complete cycle of vertical migration when an overhead light source is cycli­cally varied in intensity. A ‘dawn rise’ to the surface at low intensity is followed by the descent of the animals to a characteristic maximum depth. The animals rise to the surface again as the light decreases, and finally show a typical midnight sinking. The light intensities at the level of the animals in this experiment are of the same order as those which have been reported in field observations; the time course of the movement also repeats the natural conditions in the field. The process is independent of the duration of the cycle and is related only to the variation in overhead light intensity. At low light intensity the movement of the animal is determined solely by positive photo-kinesis; the dawn rise is a manifestation of this, and is independent of the direction of the light. At high light intensities there is an orientation response which is superimposed upon an alternating positive (photokinetic) phase and a negative phase during which movement is inhibited. The fully oriented animal shows a special type of positive and negative phototaxis, moving towards the light at reduced light intensities and away from it when the light intensity is increased. In this condition it follows a zone of optimum light intensity with some exactness. Experiments show that an animal in this fully oriented condition will respond to the slow changes of intensity characteristic of the diurnal cycle, while being little affected by tran­sient changes of considerable magnitude.

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