488 



W. D. Bonner, jr. 



in addition to the {a + (h) band at 598 m//, and the c band at 549 m/i, two 

 well defined peaks at 558 and 554 m/x. These latter two components are seen 

 as one absorption band when observed with the microspectroscope at room 

 temperature. 



In order to delineate the cytochromes of corn pollen more clearly, a 

 homogenate, prepared in 01 m sodium phosphate buffer was studied. The 



■CAULIFIQWER. 



A0D.=0.01 



Ox.-SjO^ 



Ox.-DPNH/CN" 



Ox.-DPNH/HOQNO 



■I I I I I I I I I I I I I 



520 550 580 610 



Wovelenglh (m;j) 



Fig. 5. Difference spectra (at -190°C) ob- 

 tained from cauliflower mitochondria. Curve 

 A, oxidized minus dithionite; Curve B, 

 oxidized minus DPNH and cyanide; Curve 

 C, oxidized minus DPNH and HOQNO. 



Fig. 6. Diff"erence spectra (at -IWC) 

 obtained from etiolated black valentine 

 bean mitochondria. The spectra repre- 

 sent the difference in absorption between 

 an oxidized mitochondrial suspension 

 and suspensions reduced with A, dithio- 

 nite; B, cyanide and DPNH; C.DPNH 

 and HOQNO. 



low temperature spectra resulting from this study are shown in Fig. 4. 

 Inspection of this figure shows that the dithionite reduced homogenate gives 

 essentially the same spectrum as does the whole pollen suspension. A 

 remarkable effect is observed on reduction of the homogenate by DPNH in 

 the presence of cyanide, under wliich conditions the ^b" components disappear 

 almost entirely and only cytochromes c and {a + ^3) remain reduced. Such 

 behaviour is very different from yeast and muscle preparations, but has been 

 demonstrated in two aroids Arum maculatuni (Bendall and Hill, 1956) and 

 Syinplocarpus foctidus (Chance and Hackett, 1959; Yocum and Bonner, 

 unpublished work). 



