459 



S. S. Brody and M. Brody 



attributed to the presence of various sized pigments aggregates (39) or 

 association of pigment with various proteins or lipoproteins (19,55). The 

 relative intensity of the three peaks has been regarded as a manifestation 

 of the concentration of the corresponding complexes. 



Evidence for two forms of chlorophyll was actually given earlier for green 

 plants than for bacteria by Albers and Knorr ( 1 ), who resolved two absorp- 

 tion maxima - at 683 m|j. and 670 mfj.. However, these workers considered 

 the two peaks as representing different chemical states of chlorophyll rather 

 than associated states of chlorophyll. Their early observations were con- 

 firmed by French and co-workers (27) and Brown and French (15) who used 

 a derivative absorption spectrometer and resolved not only the absorption 

 m^axima at 673 and 683 but two other nnaxima at 694 mfj. and 707 m|jL. French 

 and co-workers(28,Z9) have demonstrated these forms of chlorophyll in a wide 

 variety of organisms. 



Krasnovsky and Kosobutskaja (37) noted that when etiolated leaves are 

 placed in bright light for one minute, the newly formed chlorophyll a^ 

 exhibits an absorption maximum at 670 m|a. After several hours of illumina- 

 tion the maxinnum shifts to 687 nn|j.; Krasnovsky and Kosobutskaja attributed 

 this shift to aggregation and binding of some of the chlorophyll. This inter- 

 pretation has been further extended to bacteria and algae (40,54). 



Induced changes in absorption have yielded spectra with maxima at 705, 

 678 and 660 m|uL (18,36); these peaks have been attributed to an unknown pig- 

 nnent, chlorophyll a, and chlorophyll b, respectively. By low temperature 

 absorption spectroscopy of leaves, Butler (l6) has also shown the presence 

 of the 705 mfj. absorption band. 



A summary of the absorption maxima cited above and the methods used to 

 obtain them are given below. 



Table I 



Absorption Maxima of Chlorophyll Reported in Vivo , in mfj. 



Differential Absorption 707 695 683 673 



Induced Changes 705 678 



Greening Process 687 670 



Absorption at Low Tennps. 705 



3. Evidence Based on Excitation Spectra: Excitation of fluorescence of 

 algae at low temperatures has shown that the absorption spectrum of the 

 chlorophyll aggregate differs from the mononner (7, I6 ). Butler (16) found 

 that one of the bands which gives rise to emission from the aggregate (at 

 7Z0 m|j.) has an absorption maximum at 705 m|jL. 



