GROWTH MOVEMENTS 



1079 



corresponding growth reactions for suitable intensities. In unilateral 

 light equal bending is shown for corresponding intensities, first positive, 

 negative, then positive. Light curvature and light-growth reactions 

 are parallel processes. The stronger 

 the light-growth reaction in a given 

 wave-length region, the greater will 

 be the tropic response. The seed- 

 ling's "choice" in the compensation 

 experiments between two wave-length 

 ranges is always that which corre- 

 sponds to the stronger growth reaction. 

 Bachmann and Bergann (2) review 

 the early work of Blaauw and correct 

 the energy values of his data for light 

 absorbed by CUSO4 and water filter, 

 also surface reflections and color filter, 

 in order to compare his results with 

 those obtained by Bergann. The 

 results of Sonne and Koningsberger 

 are also 



450 



(m)i) 



Fig. 3. — Graphs showing the sensi- 

 tivity of Avena saliva to wave-lengths of 

 light (continuous line) as compared with 

 the corrected values of Blaauw (crosses), 

 corrected and compared, of Sonne (circles), and of Koningsberger 



These data are represented graphically ^BerglT,^^^''^^^ ' ^^"""^ bachmann and 



in Fig. 3, in which the continuous 



line is the sensitivity curve, the data from Blaauw's work are 



indicated as small crosses, those of Sonne as circles, and those of 



Koningsberger as horizontal lines. 

 The multiplier for Blaauw's data in the 

 short wave-length region is 2.5. 



From this work it is concluded 

 that there are two maxima in the 

 phototropic curve and that these 

 correspond in general to the maximum 

 light absorption regions of chromo- 

 440 480 520 560 600 MO lipoids. It appears that the photo- 



Wave- length -m^i . i i «. 



Fig. 4.-Graph8 showing the relative ^''^P^^ CUrvatureS m the different wave- 

 efficiencies of different wave-lengths in length regions follow the absorption 



their phototropic action on Phycomyces ^r i:„ua u -a u j. j.l • 



hlakesleanus (horizontal lines), on Phyco- ^^ ^^g^* ^^ Specific SubstanCCS Or their 



mi/ces widens after Blaauw (solid circles), compounds ill these same regions. 



and on Pilobolus after Parr (open rpi -a- -a c ^.i. 



circles). (From CaaUe, 16.) ^he sensitivity of the sporangi- 



ophores of Phycomyces to light of 

 different wave-lengths was investigated by Castle (16). The sporangio- 

 phores were placed between two light sources. The intensities were 

 adjusted until the phototropic effects of the different spectral regions 

 were equal. At this point the efficiency of each region was taken as 

 proportional to its relative energy content. Wratten filters were used 



too 



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