INDOLE COMPOUNDS IN PHOTOINDUCED PLANTS 



A. J. Vlitos| 

 Boyce Thompson Institute for Plant Research, Yonkers, New York 



INTRODUCTION 



Indole compounds are known to regulate vegetative growth of plants but 

 their influence on flowering has not been extensively studied. There is 

 considerable evidence that the response to photoperiodic treatment can be 

 modified by 3-indoleacetic acid (lAA). Application to short-day plants may 

 inhibit flowering (Bonner and Liverman, 1953; Fisher and Loomis, 1954); 

 an effect which can be counteracted by subsequent treatment with antiauxin. 



Treatment of long-day plants with auxin may reverse the photoperiodic 

 response since it prevents their flowering when held under long-day condi- 

 tions and induces floral initiation under short-day conditions. Because of 

 these observations Fisher and Loomis (1954) have postulated that flowering 

 of Lincoln soybeans may depend upon a proper balance between auxin and 

 a flowering hormone. 



Further evidence in support of this hypothesis might be obtained by 

 determining effects of photoinduction on the auxin content of plants. 

 Studies were undertaken, therefore, to determine whether there was a 

 decrease in the amount of indole compounds present in typical short-day 

 plants such as Maryland Mammoth tobacco and Biloxi and Lincoln soybeans 

 when they were photoinduced. The methods of extracting, identifying, and 

 measuring quantitatively the various indole compounds before and after 

 photoinduction are described in this paper. 



PAPER CHROMATOGRAPHY OF INDOLE DERIVATIVES 



Most of the work with quantitative auxin assays has been based upon 

 nonspecific, biological assays (i.e. Avena coleoptile curvatures or Avena 

 straight growth tests). Therefore, the precursors of lAA in plant tissues, 

 examined by means of biological assays, have not been adequately considered 

 in photoperiodic studies. With the advent of paper chromatography, a 

 technique is now available to study, individually, the role of free lAA, lAA 

 bound to proteins, and various precursors which can be converted into lAA 

 in flowering. In addition, paper chromatography permits a direct study of 

 the effect of naturally-occurring inhibitors on an auxin of known chemical 

 composition. 



In 1953 we described a method for the quantitative determination of lAA 

 and other indole compounds in plant tissues (Vlitos and Meudt, 1953). The 

 technique is based upon paper chromatographic methods and upon the 

 measurement of the maximum density of spots developed with /7-dimethyl- 

 aminobenzaldehyde. A typical standard curve for lAA is reproduced in 



t Holder of the Carbide and Carbon Chemicals Company Fellowship at the Boyce 

 Thompson Institute. 



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