8 

 extracted. The process utilized is similar to that used in the produc- 

 tion of antibiotics (Borrow et al . , 1955; Marth et al . , 1956; Russell, 

 1974). 



Relative Potency of Gibberellins 



The standard method of assessing the potency of a gibberellin is by 

 various bioassay techniques (Bailiss and Hill, 1971; Reeve and Crozier, 

 1974). Bailiss and Hill (1971) conducted an extensive review of gib- 

 berellin bioassay techniques and listed 33 test systems which were 

 based on such diverse processes as coleoptile, leaf sheath, epicotyl, 

 hypocotyl and radicle growth, bud dormancy, seed germination, induction 

 of a-amylase synthesis, leaf expansion and senescence, and flower and 

 cone induction. Interpretation of bioassay data should be done 

 cautiously because individual bioassays exhibit a great deal of 

 species and even variety specificity (Reeve and Crozier, 1974). As 

 noted by Reeve and Crozier (1974), the barley aleurone and cucumber 

 hypocotyl tests only exhibit response to a limited number of 

 giberellins, whereas the dwarf rice bioassay responds to almost all 

 gibberellins. 



Based on the overall assessment of the relative responses obtained from 

 barley aleurone a-amylase synthesis, dwarf pea growth, lettuce and 

 cucumber hypocotyl growth, and Tan-ginbozu drawf rice microdrop bio- 

 assays, Reeve and Crozier (1974) assessed the relative activities of 38 

 gibberellins. This ranking indicates that the highest activities are 

 provided by GA. , GA 3 , GA ? , and GA 32 . Good responses were also induced 

 by GA,-, GA 6 , GA 26 , and GA 37 but not of the same order of magnitude. Other 



