R. S. DE ROPP 



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salts, and thiamin. On this medium normal stem tissue of sunflower grew 

 slowly, was green in color, woody in texture, and tended to differentiate 

 roots. The tumor tissue, on the other hand, grew rapidly as a white, 

 rather friable mass and did not differentiate organs. Bacteria-free crown- 

 gall tumor tissue was subsequently isolated from primary galls on sun- 

 flower (36), from galls on Periwinkle that had been freed of bacteria 

 by heat treatment (47), also from galls on marigold and Paris-daisy 

 (23), scorzonera, Jerusalem artichoke (20,19), ^^^^^ vinifera, Opiintia, 

 Carthammis, Abutilon, and Nicotiana (29). It seems, in fact, that these 

 galls tend, as they grow older, to become free of the causal organism. 



The isolation of bacteria-free crown-gall tumor tissue made possible 

 a closer study of the physiology of this tissue. The respiratory behavior 

 of crown-gall tumor tissue was compared with that of healthy tissue by 

 White (48), who found no significant change in the quahtative respira- 

 tory picture of tumor tissue but detected a lowering of the respiratory 

 level. The insensitivity of sunflower crown-gaU tissue to indoleacetic 

 acid, napthaleneacetic acid, and indolebutyric acid was contrasted by 

 de Ropp (13) with the extreme sensitivity of healthy sunflower stem- 

 tissue to these substances. Gautheret (19) working with artichoke crown- 

 gall tissue made similar observations. Riker, Hildebrandt, and coworkers 

 (23,35) have carried out extensive studies on the nutrient requirements 

 of bacteria-free crown-gall tissue showing that crown-gall tumor tissue 

 of various plants can use dextrose, levulose, and sucrose as sources of 

 carbon for growth but have little or no ability to use organic acids or 

 alcohols. Nitrate and urea proved to be the best sources of nitrogen of 

 the various compounds tested. Several of the amino acids tested proved 

 to have an inhibiting action on growth. 



The influence of crown-gall tumor tissue on healthy tissue of the 

 same plant was studied by de Ropp (12) using the technique oiin vitro 

 grafting. Induced tumors having a characteristic anatomical structure 

 developed on many of the stem fragments to which tumor tissue had 

 been successfully grafted. These induced tumors, on isolation, proved 

 to have the physiological properties of crown-gall tumor tissue although 

 they had apparently arisen from the cambium of the stem fragment. 

 It was concluded that a tumefacient factor exists in crown-gall tumor 

 tissue capable of being transferred to normal tissue across a graft union. 

 Attempts to transmit the tumefacient principle by other means were 

 not successful (14). Induced tumors were subsequently obtained on 



