MOVEMENTS OF CHLOROPLASTS 



681 



in Table 22.1. This table indicates that in blue-violet light increase in 

 transmittance may be by as much as one-third (from 19 to 25%). 



Table 22.1 



Transmittance of a Leaf of Adiantum cuneatum 

 (after Schanderl and Kaempfert 1933) 



Light exposure 



In diffuse room light, % 



After 4 hr. exposure to sun, %. 



White 



light 

 (inchiding 

 infrared) 



Red 



and 

 infrared 



31 

 37 



34 

 42 



Yellow 



and 



green 



16 



18 



Violet 

 and 

 blue 



19 

 25 



With some plants {e. g., T radescantia ?>mrfis). Schanderl and Kaempfert 

 found a reversal of the effect after the first half hour of illumination {cf. 

 fig. 22.6) ; they attributed it to increased scattering, caused by the forma- 

 tion of starch grains. 



Schanderl and Kaempfeit did not prove that increased transparency of sun-exposed 

 leaves was due entirely to reorientation of the chloroplasts, and not, e. g., to a partial 

 bleaching of the pigments. However, the results of Willstatter and StoU (1918), which 

 showed no change in chlorophyll concentration after strong illumination {cf. Vol. I, 

 chapter 19, page 549), argue against the second explanation. 



100 



90 



80 



»? 70 



- BLUE LIGHT 



. X««1(-X-)H ( "X ^X- 



/ 



/BLUE-GREEN LIGHT 



YELLOW-GREEN LIGHT/ 



L5 



20 2.5 3.0 3.5 4.0 



LOG INTENSITY, lO^cal/cm.^ hr. 



45 



Fig. 22.7. Orientation of chloroplasts in Funaria in light of different color 



(after Voerkel 1934). 



The phototaxis of the chloroplasts is caused mainly by blue-violet 

 Hght and is entirely absent in red light (fig. 22.7). It must thus be sensi- 

 tized by the carotenoids rather than by chlorophyll. This is not a proof 



