CURRENT LITERATURE 





NOTES FOR STUDENTS 



Light and growth. — Bakhuijzen 1 gives a theoretical discussion of the 

 possibility of photo-growth response as the basis of phototropic reaction. 

 He accepts Blaauw's 2 view that the effect of light on the longitudinal growth 

 is the basis of phototropic response, which is the resultant of the effect of 

 unilateral light on the growth of the two flanks of the plant organ. This is 

 De Condallis' old theory of phototropic response. He calculates Vogt's 

 data on the Avena coleoptile, which he believes confirms this view. From 

 this work he believes that the retarding effect of a given dosage of light accounts 

 J for the phototropic response, and that the later accelerating effect is not 



involved. He finds that the effect of omnilateral fore-illumination on later 

 phototropic response to unilateral illumination can be explained by the joint 

 effect of the two kinds of illumination upon the growth of the two flanks, and 

 that there is no necessity of assuming that omnilateral illumination changes 

 the sensitiveness of the organ. This agrees more nearly with Arisz' interpre- 

 tation of his results, and is quite opposite to the view of Bremekamp. Clark's 

 results, in which he found that omnilateral fore-illumination increased the 

 sensitiveness of the organ in negative phototropic response, can be similarly 

 explained. The time during which the light is applied, as well as the total 

 energy, is important, and this will explain the results obtained by unilateral 

 illuminations followed by omnilateral illuminations on the photo-growth basis. 



Laurens and Hooker^ working on Volvox with various ray lengths of 

 equal energy value, find that wave length A. 494 /x/x has the highest stimulative 

 value, and that the efficiency decreases with both shorter and longer wave 

 lengths. The measurements were made both on the basis of relative duration 

 of the presentation time and the relative rate of locomotion (and precision of 

 orientation). Other authors have found the optimum for photo-perception and 

 photo-growth response for various forms in this general region of the spectrum. 



Guttexburg 4 has shown by several methods that in the coleoptile of 

 Avena saliva the total plane of unilateral illumination is quite as important in 



1 Bakhuijzen. H. L.. Van* de Sande, Photo-growth reaction and disposition to 

 light in Avena saliva. Konin. Akad. Weten. Amster. 22: 1-16. 1919. 



2 Bot. Gaz. 59:67-68. 1915. 



3 Laurens. H., and Hooker, H. D.. Jr., Studies on the relative physiological 

 value of spectral light. II. The sensibility of Volvox to wave-lengths of equal energy 

 content. Jour. Exp. Zool. 30:345-368. 1920. 



4 Guttenburg, H. V., Untersuchungen iiber den Phototropismus der Pflanzen. 

 I. tjber die Abhangigkeit der phototropen Krscheinungen von der Grosse der Beleuchte- 

 ten Flache. Ber. Bot. Gesells. 37:299-304. 1919. 



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