Natural auxins 



field of plant tissue cultures. It is well known that certain tissues can be 

 grown in vitro if the medium contains an auxin, whereas others can grow on 

 sugar and mineral salts alone (see Gautheret, 1954). It has also been shown 

 that the extract of the tissues which can grow without added auxin in the 

 medium are active in the Avena curvature test (Kulescha, 1951), but it is 

 not verv clear if the difference in the auxin requirement is due to an increased 



Figure 22. Histograms showing the bio- 

 logical activity of chromatograms of tissue 

 culture extracts run in hopropanol + water 

 (80;20) and assayed with first internode 

 sections. PTN = crude ether extract (3 hours 

 at 0°C) of 6 g { fresh weight) of Partheno- 

 cissus tricuspidata, normal tissue, grown in 

 vitro for 4-5 months on a medium containing 

 sucrose, mineral salts, and lAA (50 yjl.). 

 After this length of time, the added lAA had 

 been completely exhausted. PTH = crude ether 

 extract (2-5 hours at "C) of 4-5 g {fresh 

 weight) of Parthenocissus tricuspidata 

 'habituated' tissue, grown for 4-5 months on a 

 medium containing only sucrose and mineral 

 salts. PTG = crude ether extract (2 hours at 

 0°C) of 5 mg (fresh weight) of Partheno- 

 cissus tricuspidata crown-gall tissue, grown 

 for 2-5 months on a medium containing ordy 

 sucrose and mineral salts. 



08 0¥ 0-6 OS 10 



R _* 



/ 



endogenous synthesis (Henderson and Bonner, 1952), or to a reduced destruc- 

 tion (Piatt, 1954). Using three types of tissues from the same species, 

 Parthenocissus tricuspidata (Sied. and Zucc.) Planch., namely the 'normal' 

 tissue (requiring added auxin), the tissue 'habituated to auxin' (derived from 

 the normal strain, but capable of growing without added auxin), and the 

 crown-gall tissue (growing without added auxin) isolated by Morel (1948), 

 we have studied the auxins which can be detected after a 3-hour ether 

 extraction at 0°C. About 5 mg (fresh weight) of tissue were generally used 

 and the extracts were not purified. The chromatograms were assayed with 



26 



