A. ir. r.ALsroN and RAVINDAR KAUR 697 



TABLE 4 



Effect of the Photoperiod of the Parent Plant on GA-IAA Synergism 



IN Green Pea Stem Sections 



photoperiod plants show GA-IAA synergism bnt longer pieces do 

 not. The reasons for these curious relationships are at present com- 

 pletely obscure. 



In previous experiments (9) it has been demonstrated that momen 

 tary exposure of section or stem pieces to GA induces effects almost 

 as great as those caused by continuous exposure. Table 6 demon- 

 strates that exposure of 5 mm sections from 8-hour photoperiod plants 

 to as little as 1 minute of 10—^ M GA suffices to induce the synergism 



TABLE 5 



Effect of the Length of Stem Pretreated with GA on Degree of Subsequent 

 Synergism with IAA in Green Pea Stem Sections Excised from 8-, 16-, and 

 24-HOUR Photoperiod Plants. Basal Pretreatment Time in GA was 30 Minutes. 



Stem 

 Photoperiod length Endogenous Growth of sections 



hours cm growth (mm) (mm in excess of endogenous) 



IAA GA IAA + GA 



Obs. - 

 Calc. Obs. Calc. 



2 0.78 2.36 0.30 2.66 3.56 0.90 



8 5 0.81 2.48 0.26 2.74 3.20 0.46 



10 0.86 2.32 0.30 2.62 3.08 0.46 



2 0.98 2.38 0.51 2.89 3.01 0.12 



16 5 1.05 2.75 0.43 3.18 3.44 0.26 



10 1.38 2.41 0.18 2.59 3.11 0.52 



2 1.19 2.90 0.32 3.22 3.83 0.61 



24 5 1.17 3.79 0.43 4.22 3.97 -0.25 



10 1.29 3.48 0.15 3.63 4.00 0.37 



