174 AKNUAL REPORT SMITHSONIAN INSTITUTION, 1963 



Plastids of flowering plants grown in the dark are converted to 

 functional chloroplasts in the light. The antibiotic chloramphenicol 

 partially inhibits light- dependent synthesis of whole leaf and chloro- 

 plast protein, and chloroplasts from chloramplienicol-treated leaves 

 lack the ability to catalyze light-dependent formation of TPNH 

 (reduced triphosphopyridine nucleotide) and ATP (adenosine tri- 

 phosphate) which are needed for photosynthetic carbon dioxide fixa- 

 tion. Thus, nonfunctional plastids lack a number of structural pro- 

 teins necessary for the generation of TPNH and ATP. Methods of 

 isolating chloroplasts active in photoproduction of TPNH and ATP 

 were examined. An unidentified inactivator was found in leaf homo- 

 genates. The presence of this inhibitor accounts for the previous 

 difficulties encountered in obtaining chloroplasts active in photopro- 

 duction of TPNH and ATP. 



The proteins of functional chloroplasts from treated and untreated 

 leaves differ. Purified plastids from treated leaves contain a larger 

 fraction of protein that can be made water soluble. Immunological 

 analysis, however, shows that the soluble fraction from chloroplasts 

 of control leaves contains more protein components. Differences are 

 related to structural differences visualized with the electron micro- 

 scope. 



Unlike flowering plants, many algae form chloroplast pigments in 

 the dark. However, differences in quantity and quality of light have 

 been reported to affect pigmentation and photosynthetic capacity. 

 A number of littoral diatom isolates were found to grow well in the 

 dark. Similar pelagic isolates are being sought. Methods of quanti- 

 tatively extracting chloroplast pigments are being developed to com- 

 pare differences in pigmentation between organisms grown in light 

 and dark. 



Marine organisms are peculiarly suitable for fundamental iuA^^esti- 

 gation of radiation responses, and a section was organized within the 

 division for marine biology research. The long-tenn aim of this 

 study is toward establishing an adequate understanding of the physi- 

 ology and biochemistry of the occurrence, behavior, and potential har- 

 vest of marine organisms. 



In the sea, algae carry out the conversion of light energy to chemical 

 energy. Phosphorus compounds are involved and play an important 

 role in the determination of the bulk and growth rates of the algae. 

 A nmnber of types of phosphorus compounds in algae have been 

 identified, quantitated, and used in structural studies. Metabolic 

 activities of these compounds have been determined by the rate of 

 incorporation of radioactive isotopes. Methylated ribose was demon- 

 strated as a component of nucleotides of RNA (ribose nucleic acid) 



