83 



The physiological state of plants in each separate evaluation also 

 contributed to the lower level of activity in the field plots. The 

 plants grown in plastic-lined metal containers (Part 1) were young, 

 rapidly growing specimens, whereas, the plants treated in Lake Dexter, 

 Florida (Part 3) were mature, spaced-! i mi ted specimens. This condition 

 was evident since the controls in Part 3 exhibited insignificant growth 

 in terms of fresh weight and number of plants produced per sq m during 

 the study. Addicott (1970) and Low (1974) supported these observations 

 by explaining the differing results from seemingly similar experiments 

 with gibberellins in terms of physiological conditions of the experi- 

 mental material, i.e., age, size, nutrient and light availability, 

 temperature, species, and type of tissue examined. 



The apparent lack of interaction or synergism observed in this study 

 is also partially explained by the above referenced comments of Addicott 

 (1970) and Low (1974). However, numerous other researchers reported 

 that synergistic interactions between gibberellins and auxin-like com- 

 pounds were due to an auxin-sparing reactions wherein the applied gib- 

 berellins inhibited or reduced endogenous concentrations of auxin 

 degrading enzymes (Brian and Hemming, 1958; Kogl and Elema 1960, cited 

 in Weaver, 1972; Galston and Purves, 1960; Sarma 1978). Such mechanisms 

 in which levels of endogenous auxins are increased by GA^ could possibly 

 account for supposedly increased sensitivity of plant tissues to reduced 

 concentrations of auxins or 2,4-D applied with gibberellins. The phy- 

 siological state of the plant and the environmental conditions of the 

 experiment could then determine the level of production of other endoge- 

 nous plant growth substances, as suggested by Low (1974). The magnitude 

 of this production could result in either additive or synergistic effects. 



