All measurements of intact leaf 02 sensitivity can be explained by the oxygenation model for glycolate formation and glycolate metabolism by established pathways. Predicting the rate of oxygenation from the underlying biochemistry is more reliable than calculating the rate of oxygenation from intact leaf gas exchange measurements. REFERENCES 1. Badger MR, TD Sharkey, S von Caemmerer: The relationship between steady-state gas exchange of bean leaves and the levels of carbon reduction cycle intermediates. Planta 160:305-313, 1984. 2. Bowes, G, WL Ogren, RH Hageman: Phosphoglycolate production catalyzed by ribulose diphosphate carboxylase. Biochem. Biophys. Res. Commun. 45:716-722, 1971. 3. Farquhar GD, S von Caemmerer, JA Berry: A biochemical model of photosynthetic C02 assimilation in leaves of C3 species. Planta 149: 78-90, 1980. 4. Farquhar GD, S von Caemmerer: Modelling of photosynthetic response to environmental conditions. In OL Lange, PS Nobel, CB Osmond, H Ziegler, eds, Encycl. of Plant Physiol., New Series, Springer Verlag, Heidelberg 12b: 549-587, 1982. 5. Jordan DB, WL Ogren: The C02/02 specificity of ribulose 1- bisphosphate carboxylase/oxygenase. Dependence on ribulose bisphosphate concentration, pH and temperature. Planta 161: 308-313, 1984. 6. Ku SB, GE Edwards: Oxygen inhibition of photosynthesis. I. Temperature dependence and relation to 02/C02 solubility ratio. Plant Physiol 59: 986-990, 1977. 7. Laing WA, WL Ogren, RL Hageman: Regulation of soybean net photosynthetic C02 fixation by the interaction of C02' 02 and ribulose l,5-diphosphate carboxylase. Plant Physiol 54: 678-685, 1974."

With the demonstration of the "triple response" in plants by Neljubow at the turn of the century, ethylene has been identified as a substance specifically affecting plant growth. Yet it took a few more decades to show that ethylene is a naturally occurring product of plants having all the characteristics of a phytohormone. Ever since much effort has been devoted to a wide variety of physiological and biochemical problems relevant to ethylene. A first meeting was organized in Israel in 1984 to bring together many people active in this rapidly expanding field of experimental research. It is the aim of the present symposium to provide once more a forum at which researchers might expose and comment progress in their work over the last few years. Speakers were invi ted and their contri buti ons ordered ina number of sessions, each of which was centered on a particular topiC. Much of the benefit came from ensuing discussion sessions which were conducted with much competence and expertise by Anderson, Ben-Arie, Goren, Morgan and Osborne. All of these colleagues are recognized leaders in ethylene research today and the organizers owe a very special gratitude to them for their substantial contribution to the programme. It is well to remember the friendly atmosphere, so essential to the success of the whole meeting and so much enjoyed by every partiCipant. Prompt publi ca tion of the papers was made possi ble by the camera-ready procedure offered by the publisher.

This book contains the proceedings of a symposium, held in the Limburgs Universitair Centrum, Diepenbeek, Belgium, from July 23 to 29, 1978.1t can be considered as a continuation of the publication 'Environmental and Biological Control of Photosynthesis' (Dr. W. Junk b.v. Publishers, The Hague, 1975). In the last meeting, however, emphasis was much more on the biological control of photosynthesis. The sequence of the different topic sessions and papers on the symposium programme is maintained in the publication; the editors are aware of the fact that different contributions might figure equally well in more than one session. A limited number of speakers was invited; time for discussion therefore could generously be provided to the audience. We thank all the participants for their active contribution to the success of this conception of organizing a meeting. The quality of a discussion session also depends on the performance of the discussion leader; thanks are due to Drs. G. Bernier, J.J. Landsberg, C.J. Pearson, R. Sachs, I.A. Tamas and K.J. Treharne who took the chair with scientific authority and enthusiasm. In order to keep in memory the flavor of this aspect of the meeting, an account of the discussion on one particular topic, the relationship between photosynthesis and flowering, was made by Dr. R. Sachs (reporter) and Dr. G. Bernier (discussion leader) and is published here after the reports on this topic.

All measurements of intact leaf 02 sensitivity can be explained by the oxygenation model for glycolate formation and glycolate metabolism by established pathways. Predicting the rate of oxygenation from the underlying biochemistry is more reliable than calculating the rate of oxygenation from intact leaf gas exchange measurements. REFERENCES 1. Badger MR, TD Sharkey, S von Caemmerer: The relationship between steady-state gas exchange of bean leaves and the levels of carbon reduction cycle intermediates. Planta 160:305-313, 1984. 2. Bowes, G, WL Ogren, RH Hageman: Phosphoglycolate production catalyzed by ribulose diphosphate carboxylase. Biochem. Biophys. Res. Commun. 45:716-722, 1971. 3. Farquhar GD, S von Caemmerer, JA Berry: A biochemical model of photosynthetic C02 assimilation in leaves of C3 species. Planta 149: 78-90, 1980. 4. Farquhar GD, S von Caemmerer: Modelling of photosynthetic response to environmental conditions. In OL Lange, PS Nobel, CB Osmond, H Ziegler, eds, Encycl. of Plant Physiol., New Series, Springer Verlag, Heidelberg 12b: 549-587, 1982. 5. Jordan DB, WL Ogren: The C02/02 specificity of ribulose 1- bisphosphate carboxylase/oxygenase. Dependence on ribulose bisphosphate concentration, pH and temperature. Planta 161: 308-313, 1984. 6. Ku SB, GE Edwards: Oxygen inhibition of photosynthesis. I. Temperature dependence and relation to 02/C02 solubility ratio. Plant Physiol 59: 986-990, 1977. 7. Laing WA, WL Ogren, RL Hageman: Regulation of soybean net photosynthetic C02 fixation by the interaction of C02' 02 and ribulose l,5-diphosphate carboxylase. Plant Physiol 54: 678-685, 1974."

The present volume "Excitation Energy and Electron Transfer in Pho. tosynthesis" is dedicated to a colleague and dear friend Warren L. But ler. I first met Warren when he visited the University of Illinois at Ur bana during the early sixties; he left an indelible impression on me as a person with warmth and enthusiasm. Initially, he was someone I looked to for guidance, but later we also became friends. Whenever I passed through Los Angeles, I always telephoned Warren and often end ed up taking a plane to San Diego to stay with two wonderful people, Warren and his wife Lila. His invitations could never be refused. Below I reproduce the words of Herbert Stern on Warren L. Butler's life; these words express my sentiments as well as those of many of Warren's friends: ''A lifetime of acedemic creativity criss-crossed by streaks of highbrow and lowbrow fun. There is no summary to this adventure be cause we can neither make nor proclaim an end. Warren has bequeathed us his garden of academic treasures. It is ours to keep and tend. There is lots of joy in our many recollections of Warren's life and sorrow's foil can only brighten the brightness that the joy radiates."

This volume contains the papers, presented during a conference, organized jointly by the "Opzoekingsstation van Gorsem" and the "Limburgs Universitair Centrum", Belgium from 22 to 27 August 1982. For this third meeting, the chosen topic was the effect of different stresses on photosynthesis. Most of the research in this field is realized on water stress and temperature stress; this situation is refllected in the conference programme. However, the imp- tance of the other factors such as light, CO , salinity, anaerobiosis, was 2 also emphasized especially during the important discussion sessions. We express our gratitude to Drs. J. Gale, P. Jarvis, G.H. Krause, P.E. Kriedemann and P.S. Nobel for their excellent leadership during the discussion sessions. Particular thanks are also due to Dr. H.~i. Woolhouse who gave us an excellent inaugural address and whose erudition largely contributed to the interest of the discussions. For the first time in our experience of editors, we decided to use camera ready copies in order to publish more rapidly the proceedings and at a lower price. For a lot of reasons (among other things the bad choice of type of letter to be used and the choice of instructions to authors which were not perfectly followed by the authors), the technical presentation of this book will appear as non homogeneous; we accepted this lack of homogeneity with the hope tbat the publication time would be shorter in spite of the fact that, some authors delivered their manuscript with delay.

With the demonstration of the "triple response" in plants by Neljubow at the turn of the century, ethylene has been identified as a substance specifically affecting plant growth. Yet it took a few more decades to show that ethylene is a naturally occurring product of plants having all the characteristics of a phytohormone. Ever since much effort has been devoted to a wide variety of physiological and biochemical problems relevant to ethylene. A first meeting was organized in Israel in 1984 to bring together many people active in this rapidly expanding field of experimental research. It is the aim of the present symposium to provide once more a forum at which researchers might expose and comment progress in their work over the last few years. Speakers were invi ted and their contri buti ons ordered ina number of sessions, each of which was centered on a particular topiC. Much of the benefit came from ensuing discussion sessions which were conducted with much competence and expertise by Anderson, Ben-Arie, Goren, Morgan and Osborne. All of these colleagues are recognized leaders in ethylene research today and the organizers owe a very special gratitude to them for their substantial contribution to the programme. It is well to remember the friendly atmosphere, so essential to the success of the whole meeting and so much enjoyed by every partiCipant. Prompt publi ca tion of the papers was made possi ble by the camera-ready procedure offered by the publisher.

This book reports the proceedings of a meeting held in the 'Limburgs Universitair Centrum' , Diepenbeek, Belgium, August 26 to 30, 1974. In convening this meet ing, my aim was to bring together a small number of specialists working on photosynthesis of course but also always keeping in mind that plants are in fluenced by their environment (temperature, light quality and intensity, air com position, daylength . . . . . ) and can differently react according to their stage of deve lopment. In general, all these specialists work on whole plants cultivated in well known conditions (they are not 'market spinach specialists') but, when necessary, give up the idea of measuring photochemical activities in isolated they don't chloroplasts, enzyme kinetics . . . etc. It is noticeable that about 50% of them are working in laboratories directly involved with applied research in agriculture or forestry. The format of the meeting was intentionally kept small but it allowed generous time for discussion; thanks are due to Drs. O. BJOERKMAN, J. W. BRADBEER, M. M. LUDLOW and C. B. OSMOND for taking the chairs during these discussions. In such a small meeting, the choice of invited scientists was really a personnal one and thus reflected my own fields of interest. When planning the conference, I was continually divided between the wish for inviting other interesting people and the necessity of keeping time free for discussions.