PREFACE 



During the last twenty years, developments in the field of plant growth 

 substances have been rapid and impressive. As is well known, some of these 

 materials have found important and widespread uses in agriculture and 

 horticulture and are playing a vital role in increasing the yield of crops. At 

 the same time, research along more fundamental lines has not been neglected, 

 and, although the precise mechanism's which underlie the growth response are 

 not yet vniderstood, much progress has been made in studies on physiological, 

 chemical, and other aspects, and these investigations are being vigorously 

 pursued in many countries. Furthermore, the development of paper 

 chromatography has enabled critical investigations to be made on the auxin 

 and auxin-inhibitor status of different plant tissues. Already the literature on 

 all these fundamental aspects is very extensive and such is the rate of progress 

 that it has become essential for specialized workers within these fields to have 

 the opportimity of meeting from time to time to present and discuss their 

 results. 



In September 1953, the writer attended an International Conference on 

 Plant Growth Substances at the University of Lund, Sweden, organized by 

 Professor H. Burstrom. All those present were working within this field. 

 The high level and great value of the papers and discussions led, two years 

 later, to the idea of holding a similar Conference in England. This suggestion 

 was well received, and, as a result, workers from seven countries met at Wye 

 College from 17-22 July 1955. The present volume contains the papers 

 read at this Conference. 



For the purposes of historical record it is perhaps worth while to refer 

 briefly to previous meetings of this kind. In this connection, the writer is 

 indebted to Dr. P. Larsen for the reminder that the First International 

 Conference on Growth Substances was held in Paris in 1937. This meeting 

 was organized under the auspices of the League of Nations and the papers 

 were published as a special volume. Etudes et recherches sur les phytohormones 

 (Paris, 1938). Professor P. Boysen-Jensen was the President at this meeting 

 and Professor V. J. Koningsberger and Dr. G. S. Avery were amongst those 

 attending. The Second Growth Substance Conference, held in Wisconsin in 

 1949, was almost entirely American, Professor H. Burstrom being the only 

 representative from Europe to present a paper. The contributions, edited by 

 Professor F. Skoog and published in 1951 under the title Plant Growth 

 Substances, have undoubtedly proved of great value to all workers in the 

 field. Although only an abstract of the proceedings of the Lund Conference 

 (1953) was published, the great success of this meeting must be recorded. The 

 Wye Conference was organized along similar lines with the help of a grant 

 kindly provided by the Governing Body of Wye College. Their generosity in 

 this respect, and that of Sir William Slater, Secretary of the Agricultural 

 Research Council, is gratefully acknowledged. 



The following acted as Chairmen at the various sessions : Prof H. Veldstra, 



