EFFECTS OF HIGH-INTENSITY IRRADIATION 



125 



Fig. 9. Lettuce, var. Wonder van Voorburg. Irradiation with 30,000 

 ergs/cm^' sec. T.L. -daylight fluorescent hght. Treatment: 0, O.I, 1, 2.5, 

 and 10 /xg GA/plant. 3x = on the first and every lOth day; 30x = every 

 day. Photographed after 30 days of treatment, on Mar. 16, 1957. 



ferent doses and frequencies of GA application. Figure 9 shows a 

 selection of items chosen in this series. 



The discussed elongation effects in lettuce have no connection with 

 flower initiation. 



ADDITIONAL REMARKS 



De Lint has started investigating the elongation of Avena coleoptiles 

 in various spectral light regimes. This work is still in a preliminary 

 stage. The plant material permits the running of large series in a 

 short time. The seedlings are allowed to germinate in the dark for 2 

 days, remain in the dark for 1 day after having been planted, then are 

 irradiated for a few hours, put back into the dark, and are measured 

 after 5 days when the coleoptiles have stopped growing. 



Two subsequent 2-hr illuminations in various spectral regions (in- 



