EFFECTS OF HIGH-INTENSITY IRRADIATION 113 



Our green cabinet consists of green fluorescent tubes with a lemon 

 yellow filter (characteristics about equal to GG 11 of Schott). This 

 filter transmits fairly high energies, although the region transmitted 

 extends somewhat too far toward the long wavelengths. We plan soon 

 to remove the red radiation to determine whether this has any effect 

 on some of the results observed. 



I will briefly mention that we have three types of equipment for 

 large-surface and long-time spectral irradiation, as follows: 



1. Low-intensity spectral series (-1000 ergs/cm- sec) used for 

 day length extension following a short day in strong white (artificial) 



light. 



"2. High-intensity spectral series (level ~ 40,000 ergs/cm'- sec </> 

 sphere), described above. 



3. Intensity ranges from very high to very low in three spectral 

 regions, blue, yellow, and near infrared, permitting the study of 

 intensity effects in narrow spectral regions. 



The experiments reported in this paper were carried out principally 

 with the second and third types of equipment. 



STEM ELONGATION AND FLOWERING IN Hyoscyamus 



The results to be discussed were obtained with Hyoscyamus, annual 

 strain, which was also used for studying the effects of gibberellic acid. 

 Stolwijk and Zeevaart (1955), working in our laboratory, had studied 

 flowering of these plants under high-intensity treatment in separate 

 spectral regions. Stem elongation and flowering were very rapid in 

 violet, blue, and red + infrared, namely, red + 300% infrared (ob- 

 tained by incandescent light + red filters), and also in red + 30% 

 infrared (infrared "top" on red cabinet, see above). Stem, elongation 

 and flowering were very much delayed or absent in green, yellow, and 

 red. Curry and Wassink (1956) studied flowering of Hyoscyamus 

 under similar conditions in greater detail, in combination with the 

 effect of gibberellic acid. Of special interest were the rapid elongation 

 and flowering in the blue light. Since the blue originally used con- 

 tained some near infrared, we attempted to decrease this as much as 

 possible by using the blue plastic filter (Plexiglas B27, alt, of Rohm 

 & Haas, Darmstadt, Germany) mentioned above; we used a cabinet 



