116 PHOTOCONTROL OF GROWTH 



Fig. 3. Two plants from green light with 10 /xg GA applied daily, 

 Experiment 2 (Curry and Wassink, 1956), photographed Oct. 11, 1956, 

 after 68 days. 



Also, a blue cabinet was introduced with red tubes (+ red filter) on 

 top. After 15 days, the expected changes in appearance were 

 already evident. The plants then were (for technical reasons) trans- 

 ferred to a short day in white fluorescent light, where the phenomena 

 developed further. The plants in blue and in both red + infrared 

 mixtures elongated, the shoots of those in blue + red top remained 

 short like those in red and green. Both types of red + infrared showed 

 no difference, confirming Stolwijk and Zeevaart's experiment. In some 

 of the plants, 2 X 10 /^g GA was administered, on the first or on the 

 last long day (colored light). In these plants stems also developed in 

 the red, green, and red + blue series, although they were much shorter 

 than in the infrared and blue series. 



The elongation in the red + infrared top cabinet as compared with 

 red (containing only a small amount of infrared) and the suppression 

 of elongation in the blue by the addition of red was also observed in an 

 earlier series (Fig. 4, top) . 



If GA was given on the first day, elongation in blue and in both 



