68 i L. G. Nickell and IV. R. Tulecke 



chemically induced, habituated), all crown-gall or virus tumor tissues, 

 and the latter have been shown by Kulescha (4) to have endogenous 

 levels of auxin much greater than homologous normal tissue. 



The results with tissues cultured on media containing gibberellin 

 and/or 2,4-D suggest that these two substances operate separately. 

 This suggestion is best supported by the results with the crown-gall 

 tissues, normally grown on a synthetic medium without added auxin. 

 Added gibberellin causes a 20 per cent increase in the growth of 

 tobacco crown-gall tissue and more than a 60 per cent decrease in 

 the growth of sunflower crown-gall tissue, whereas the addition of 

 low levels of 2,4-D reduces the growth of both tissues. 



SUMMARY 



Forty-nine strains of tissue from 25 species of plants have been 

 tested for their growth response to gibberellin at 10 p. p.m. in tissue 

 culture. Depression of growth is the most pronounced effect, but the 

 growth of several tissues is promoted. Probably the most interesting 

 effect is the lethal action of gibberellin on two of the cultures. As a 

 group, monocotyledonous tissues were depressed in growth. There is 

 no apparent correlation between response to gibberellin and charac- 

 teristics of strains of tissue such as agents inducing proliferation, plant 

 parts from which the tissues were obtained, age of the cultures, or 

 media supporting tissue growth. Tests with 2,4-D and gibberellin 

 added singly and together suggest that these two growth substances 

 act separately. 



LITERATURE CITED 



1. Burklioldci, P. R., and Nickell, L. G. Atypical growth of plants. I. Cultivation 

 of virus tumors of Rumex on nutrient agar. Bot. Gaz. 110: 426-437. 1949. 



2. Chandler, C. The effect of gibberellic acid on germination and pollen tube 

 growth. Contr. Boyce Thompson Inst. 19: 215-223. 1957. 



3. Henderson, f. H. M. Effect of gibberellin on sunflower tissue culture. Nature. 

 182: 880. 1958. 



4. Kulescha, Z. Croissance et teneur en auxine de divers lissus normaux et 

 tumoraux. Annce Biol. 30: 319-327. 1954. 



5. MacMillan, J., and Suter, P. J. The occurrence of gibberellin Aj in higher 

 plants: isolation from the seed of runner bean (Phaseolus mnltiflorus). 

 Naturwis. 45: 46. 1958. 



6. Netien, G. Action des gib!)crcllines sur la culture des tissus vcgctaux cultiv& 

 in vitro. Compt. Rend. Acad. Sci. Paris. 244: 2732, 2733. 1957. 



7. Action de la gibberelline sur diff^rents types de tissus vcgctaux cultiv<^s 



in vitro. Compt. Rend. Acad. Sci. Paris. 247: 1645-1647. 1958. 



8. Nickell, L. G. Embryo culture of weeping crabapple. Proc. Amer. Soc. Hort. 

 Sci. 57: 401-405. 1951. 



9. Radley, M., and Dear, E. Occurrence of gibbcrellin-like substances in the 

 coconut. Nature. 182: 1098. 1958. 



