GERMINATION OF LETTUCE SEED 203 



Table II. Germination at 37°C of Gibberellic Acid-Treated Seeds Held for 12 hr 

 at 22° in Darkness Interrupted by 20 min Exposure to Far-Red Light 



Far-Red Molarity of Germination 

 Treatment Gibberellic Acid after 48 hr at 37°, % 



None 14.5 



3 X 10-" 27.4 



After 2 hr 



3 X 10 " 1.7 



After 4 hr 0.4 



3 X 10-" 4.6 



After 6 hr 3.0 



3 X 10-" 8.0 



tered the seeds. The results of this experiment (Tables II and III) 

 demonstrated that gibberellic acid did not greatly protect against the 

 inhibiting effect of exposure to far-red light during the 12 hr at 22°. 

 Data in Table III demonstrate that exposure to red light immediately 

 after the far-red exposure reversed the far-red effect under conditions 

 where treatment with gibberellic acid did not. The same results were 

 obtained with concentrations of gibberellic acid as high as 2.9 X 

 lO'W (lOOOppm). 



After each of the four far-red light treatments of Table II, the in- 

 creased germination of the gibberellic acid-treated seeds over the 

 water controls was significant. If we assume that germination at 37°C 

 was not affected by gibberellic acid, these differences must have re- 

 sulted from changes induced by gibberellic acid during the 12 hr at 

 22°. Also significant was the trend of decreasing effectiveness of the 

 far-red treatment with increasing time from the beginning of the im- 

 bibition, both within the gibberellic acid-treated and the control series. 



Table III. Red Light Reversal of Far-Red Inhibition for 

 Gibberellic Acid-Treated Seeds Held at 22°C for 12 hr 



Germination after 48 hr at 37°, % 



Light Treatment" QM 3 X 10-" M 



None 23 39 



Red 24 32 



Far red 1 6 



Far red + red 26 30 



" 20 minutes exposure to red or far red after second hr at 22°. 



