NO. 14 EFFECTS OF INFRA-RED ON PLANTS— JOHNSTON 7 



of four plants each were grown under uncontrolled conditions in 

 natural light, one group placed in a west window of a room in the 

 Smithsonian tower, the other standing in the north window of the 

 basement laboratory. At the end of two weeks the plants were photo- 



Table 3 

 Plant data at harvest, expressed as averages per plant 



Radiation 



Intensity 



Low 



Distribution" V and I 



Plant group. 



Dry weight (mg) 



Tops 126 



Roots i M 



Total j 140 



Water absorbed (cc) 45 



Stem height (cm) 



Final 



Increase 



20.2 

 17.2 



Number of leaves. . 

 Order of greenness. 



Water requirement 320 



„ ■ root ^ 



Ratio wt. 



top 



16 



3 



19 



6.8 

 4-4 



4-3 



I 



High 



Daylight 



Vandl 



810 



426 



40 



466 



88 



t8.o 

 15-6 



-..8 



West 

 window 



Ratio 



Internodal index 

 stem ht. 

 no. of leaves 



Ratio 



Stem elongation 



(final ht. 



original ht.) 



4.0 



6.7 



1.6 



2.8 



igg 



31 

 230 



93 



12.7 

 9.9 



5.8 



3 



162 



30 



192 



North 

 window 



40: 



7.8 



5-4 



5-4 

 4 



16 



3 



19 



18 



5.6 

 3-5 



3-5 



2 



0.09 



3-1 



7-5 



4.5 



444 

 0. 18 



1.3 



3.^ 



956 

 o.i; 



1-4 



" V and I, visible and near infra-red radiation; V visible radiation. 



graphed and measured. The plant data obtained from these measure- 

 ments are presented in Table 3. 



In an examination of the data of this table it should be remembered 

 that the visible intensities in chambers i and 2 were approximately 

 the same. Likewise those of 3 and 4 were alike. However, in the 

 latter pair the light was much more intense. In chambers 2 and 3 



