FLUORESCENCE SPECTRA OF PLANTS 



811 



The fluorescence of green bacteria (Chlorohium mirahle), probably due 

 to "bacterioviridin" (cf. Vol. I, p. 407), was observed by Buder (1913). 



A fluorescence band at 635 m^, noted by French (1951) in a partially green leaf could 

 be due to photochlorophyll, whose absorption band lies at 620-630 ni/x in ether. French 

 estimated its position in vivo as 650 niju (from the action spectrum of chIoroph\'ll forma- 

 tion), but noted that this is incompatible with the location of the fluorescence at 635 m/x. 



The fluorescence of the phycohilins in red and blue-green algae is of 

 great interest, because it permits a study of the interaction of two different 

 fluorescent pigments in one cell. The first photograph of the fluorescence 

 spectrum of Rhodymenia, made by Dhere and Fontaine (1931), showed one 

 band in the orange (phycoerythrin) and one in the red (chlorophyll and 

 phycocj^anin). 



Van Norman, French and Macdowall (1948) determined fluorescence 

 curves of two red algae — Gigartina and Iridaea; both showed three peaks, 

 at 575 myu (phycoerythrin, cj. p. 799), 055 m^ (phycocyanin, cj. p. 800) and 

 700 m/x (chlorophyll, probably a -^ d, cf. beloAv). French (1951) gave fig. 

 24.4 for Porphyridium: Only chlorophyll fluoresces when cells are excited 

 with X 436 m^ or 450 m/x, i.e., by light absorbed by chlorophyll and caro- 

 tenoids only. Phycohilin bands develop with excitation by 470, 490, and 

 546 m/x but, even though most of the incident light is now absorbed by 

 phycoerythrin, chlorophyll fluorescence remains strong. 



u 

 o 



z 



UJ 



o 



CO 

 UJ 



cr 

 o 



3 



T~l I I I I I I I I I I I I I I I 

 436 m;i (a) 



476 m/i 



(b) 



I I I I I I I I I 



J__L 



I I I I I I 



I I I I I I I I I I I I I I I I I I I 



546mjLi (c) 



1 I I I I I 1 I I I I I I I I I I I I 



600 



650 



700 



750 



600 



650 



700 



750 



Fig. 24.4. Fluorescence spectra of a red alga when illuminated with equal energies of 

 different wavelengths. Courtesy L. N. M. Duysens. 



