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Soc. 81: 2424-2427. 1959. 



DISCUSSION 



Dr. Barton: Dr. Phinney has mentioned that genetic dwarfs are 

 controlled by genes, as of course they are, but we have found that 

 physiologic dwarfs can also be stimulated to elongate by the use of 

 gibberellic acid. These physiologic dwarfs are those of peach, apple, 

 crabapple, etc., dwarfed because the seeds were not given low tem- 

 perature pre-treatment. Is this also controlled by genes? 



Dr. Phinney: It cannot be said that a particular physiological 

 property is controlled by a single gene until the inheritance pattern 

 is known for this property. 



Dr. Galston: I would like to ask a question based on the point 

 that Dr. Barton raised, i.e., the whole problem of whether any of the 

 overgrowths noted in pathology or in commensalisms can be explained 

 in terms of abnormal production of GA or its analogs. Several years 

 ago we found that when we applied GA to some dwarf bean plants, 

 the number of nodules on the roots was depressed. This has been 

 confirmed in various ways by Dr. Brian and by Dr. Kefford, the latter 

 using sterile culture. Now, I wonder whether there is any possibility 

 that nodule formation may be in some way related to the fact that 

 the plant has a sub-optimal level of gibberellin, and that the bac- 

 terium causes a localized production of something like gibberellin, 

 which gives to the cells in that region a selective growth advantage. 

 The application of gibberellin to such a plant could remove that se- 

 lective advantage, thus repressing nodule growth. My question should 

 really be addressed either to Dr. Stodola or to Dr. Brian, who have 

 worked with microbial fermentations. Is there any evidence that any 

 organisms related to the nodule-forming forms produce anything like 

 gibberellin, either in culture or in contact with plant cells? 



Dr. Brian: There is not to my knowledge. So far as I know, there's 

 just one Gibberella fiijikuroi. There is a recent Russian claim of a 

 yeast which produces GA. So far as I know, these are the only two 

 microorganisms ever suspected of producing gibberellins. 



