5 

 preoccupation with indoleacetic acid (IAA) and synthetic auxins, 

 (2) a lack of contact with the Japanese, and (3) World War II 

 (Salisbury and Ross, 1978). Stuart and Cathey (1961) reported that by 

 1961 approximately 9 compounds had been isolated which exhibited both 

 gibberellin-like activity and structure. This number increased to 19 by 

 1965 (Russell, 1974), 29 in 1970 (Lang, 1970), 38 by 1973 (Russell, 

 1974), 44 by 1974 (Barendse, 1974) and to over 50 by 1978 (Salisbury and 

 Ross, 1978). These gibberellins have been isolated from fungi, algae, 

 ferns, mosses, and many higher plants (Barendse, 1974; Russell, 1974; 

 Salisbury and Ross, 1978). Sircar and Kindu (1960), Bhanja and Sircar 

 (1966), and Sircar et al . (1973) reported the presence of four 

 gibberellin-like substances in the shoot and root extract of 

 waterhyacinths. Russell (1974) attributes this exponential rise in the 

 number of known gibberellins to the initiation of a systematic search 

 for growth promoting compounds which was aided, as observed by Lang 

 (1970), by the simultaneous development of highly effective techniques 

 for the separation and identification of naturally occurring compounds. 

 Both Barendse (1974) and Russell (1974) indicated that due to the 

 limited number of plants examined, the total number of gibberellins 

 and their derivatives is unknown. 



Chemical and Physical Characteristics 



Gibberellins are isoprenoid compounds and are classified as 

 diterpenes (Lang, 1970; Barendse, 1974; Salisbury and Ross, 1978). All 

 gibberellins have either 19 or 20 carbon atoms which are arranged in 

 either a four or five ring system, and all have at least one carboxyl 

 group (Barendse, 1974; Reeve and Crozier, 1974; Russell, 1974; and 



