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Plant and Cell Physiology, 1967, Vol. 8, No. 3 495-508
© 1967

Article

EFFECT OF LIGHT ON THE CHLOROPHYLL FORMATION IN THE "GLUCOSE-BLEACHED" CELLS OF CHLORELLA PROTOTHECOIDES

YOSHIHIRO SOKAWA and EKJI HASE

1Institute of Applied Microbiology, University of Tokyo Tokyo
2Tokugawa Institute for Biological Research Tokyo

  1. Previous studies have shown that when Chlorella protothecoides is grown in a medium rich in glucose and poor in nitrogen source (urea), apparently chlorophyll-less cells with profoundly degenerated plastids—referred to as "glucose-bleached cells—are produced either in the light or in darkness. When the glucose-bleached cells are incubated in a medium enriched with the nitrogen source but without added glucose, an active formation of chlorophyll occurs after a certain lag period under illumination, while in darkness a very small amount of chlorophyll is formed at about the same time as in the light. The stimulating effect of light on the chlorophyll formation is not appreciably affected when the photosynthetic CO2-fixation of greening algal cells is blocked by the addition of CMU. In the present study, it was further found that the light-enhanced chlorophyll formation proceeds, although at a somewhat lower rate, under aeration of CO2-free air. All the experiments in this work were done under these non-photosynthetic conditions to exclude any influence of photosynthates.
  2. The effect of light (from daylight fluorescent lamps) on the chlorophyll formation in the glucose-bleached algal cells was saturating at about 1,000 lux. Blue light was found to be most effective; yellow, green and red light following in the order of decreasing effectiveness.
  3. When the bleached algal cells were illuminated for a short period in the lag phase of chlorophyll formation and subsequently incubated in darkness, there occurred an appreciable enhancement of chlorophyll formation in the dark. When the short illumination was applied at different times of the lag phase, the enhancement was induced to almost the same extent. But the longer the duration of the illumination during the lag phase, the greater was the enhancement of chlorophyll formation in the subsequent dark incubation. In such experiments blue light was most effective and red light least, as it was the case in the experiments of continuous illumination. An intervenient illumination of the bleached cells at lower temperatures or under the atmosphere of N2 produced little or no enhancement of the chlorophyll formation in the subsequent dark incubation.
  4. Based on these results, it was concluded that the light enhancement of chlorophyll formation in the glucose-bleached algal cells is mediated by a non-chlorophyllous photoreceptor(s), absorbing maximally blue and yellow light, and that a light-induced change of the photoreceptor is immediately followed by a certain dark (temperaturedependent and aerobic) process(es) which is connected, directly or indirectly, to the chlorophyll synthesis.

(Received August 10, 1967; )
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