94 ANNTJAL REPORT SMITHSONIAN INSTITUTION, 1960 



undertaken to determine the effects of radiant energy on this system by 

 assaying for high-energy phosphate after treatment with red and far- 

 red energy. The adenosine triphosphate (ATP) content was assayed 

 utilizing a luciferin-luciferase method, and the nucleotide phosphate 

 by absorption on activated charcoal and by the uptake of radioactive 

 phosphorus. Red, far-red irradiation did not significantly alter the 

 ATP level in hypocotyl hook tissue, but the light treatment produced 

 a marked photomorphogenic response as compared to dark controls. 

 When growth of bean hypocotyls was inhibited 40 percent by dini- 

 trophenol, the ATP level was also found to be reduced by the same 

 amount. Thus, it is indicated, although over-all growth response 

 is dependent on ATP, the ATP alone is not the controlling factor in 

 influencing photomorphogenic responses. 



Tlie effect of inhibitors of protein synthesis on chlorophyll for- 

 mation and the relationship of protein synthesis to the red, far-red 

 regulation of photomorphogenesis have been studied. Previous work 

 with bean plants has shown that, after the initial conversion of proto- 

 chlorophyll to chlorophyll, the rate of chlorophyll synthesis does not 

 reach a maximum until after at least 4 hours of continuous irradiation. 

 This lag period can be considerably shortened if leaves are irradiated 

 briefly and incubated overnight in the dark before being subjected 

 to continuous irradiation. Chloramphenicol has been found to abolish 

 the stimulatory effect of light pretreatment. Unlike nontreated 

 leaves, chloramphenicol-treated leaves do not show an increase in rate 

 of chlorophyll synthesis upon extended continuous irradiation. P- 

 fluorophenylalanine and 6-azauracil appear to affect chlorophyll 

 synthesis similarly. 



Although chloramphenicol inliibits the light-induced increase in 

 the capacity to synthesize chlorophyll, other photomorphogenic re- 

 sponses of the bean plant apparently are not inhibited. Leaves 

 irradiated in the presence of chloramphenicol accumulate considerable 

 quantities of chlorophyll. Nevertheless, they have not the capacity 

 to photosynthesize. Chloramphenicol does not affect the photosynthet- 

 ic ability of leaves greened in its absence. It has been confirmed 

 that radiant energy (700-1100 m/x) which is not effective in promoting 

 chlorophyll formation can induce the formation of the photosynthetic 

 enzyme, TPN-linked glyceraldehyde-3-phosphate dehydrogenase. 

 Another photosynthetic enzyme, photosynthetic pyridine nucleotide 

 reductase, seems to be similarly affected. 



Previous studies indicated that the lag phase of chlorophyll 

 synthesis could be lengthened by irradiation with X-rays of 5 to 10 

 kiloroentgens and that subsequent exposure to 10 minutes of white 

 light initiated recovery of the chlorophyll-synthesizing mecha- 



