FUNDAMENTAL, ECOLOGICAL AND AGRICULTURAL ASPECTS OF NITROGEN METABOLISM IN HIGHER PLANTS Developments in Plant and Soil Sciences I. J. Monteith and C. Webb. eds .• Soil Water and Nitrogen in Mediterranean-type Environments. 1981. ISBN 90-247-2406-6 2. J.c. Brogan. ed .• Nitrogen Losses and Surface Run-off from Landspreading of Manures. 1981. ISBN 90-247-2471-6 3. J.D. Bewley. ed .• Nitrogen and Carbon Metabolism. 1981. ISBN 90-247-2472-4 4. R. Brouwer. I. Gasparfkova. J. Kolek and B.C. Loughman. eds .• Structure and Function of Plant Roots. 1981. ISBN 90-247-2510-0 5. Y.R. Dommergues and H.G. Diem. eds .• Microbiology of Tropical Soils and Plant Productivity. 1982. ISBN 90-247-2624-7 6. G.P. Robertson. R. Herrera and T. Rosswall. eds .• Nitrogen Cycling in Ecosystems of Latin America and the Caribbean. 1982. ISBN 90-247-2719-7 7. D. Atkinson et al.. eds .• Tree Root Systems and their Mycorrhizas. 1983. ISBN 90-247-2821-5 8. M.R. Saric and B.C. Loughman. eds .• Genetic Aspects of Plant Nutrition. 1983. ISBN 90-247-2822-3 9. J.R. Freney and J.R. Simpson. eds .• Gaseous Loss of Nitrogen from Plant-Soil Systems. 1983. ISBN 90-247-2820-7 10. United Nations Economic Commission for Europe. Efficient Use of Fertilizers in Agriculture. 1983. ISBN 90-247-2866-5 I I. J. Tinsley and J .F. Darbyshire. eds .• Biological Processes and Soil Fertility. 1984. ISBN 90-247-2902-5 12. A.D.L. Akkermans. D. Baker. K. Huss-Danell and J.D. Tjepkema. eds .• Frankia Symbioses. 1984. ISBN 90-247-2967-X 13. W.S. Silver and E.C. Schroder. eds .• Practical Application of Azolla for Rice Production. 1984. ISBN 90-247-3068-6 14. P.G.L. Vlek. ed .• Micronutrients in Tropical Food Crop Production. 1985. ISBN 90-247-3085-6 15. T.P. Hignett. ed .• Fertilizer Manual. 1985. ISBN 90-247-3122-4 16. D. Vaughan and R.E. Malcolm. eds .• Soil Organic Matter and Biological Activity. 1985. ISBN 90-247-3154-2 17. D. Pasternak and A. San Pietro. eds .• Biosalinity in Action: Bioproduction with Saline Water. 1985. ISBN 90-247-3159-3. 18. M. Lalonde. C. Camire and J.~. Dawson. eds .• Frankia and Actinorhizal Plants. 1985. ISBN 90-247-3214-X 19. H. Lambers. J.J. Neeteson and I. Stulen. eds .• Fundamental. Ecological and Agricultural Aspects of Nitrogen Metabolism in Higher Plants. 1986. ISBN 90-247-3258-1 20. M.B. Jackson. ed. New Root Formation in Plants and Cuttings. 1986. ISBN 90-247-3260-3 21. F.A. Skinner and P. Uomala. eds .• Nitrogen Fixation with Non-Legumes. 1986. ISBN 90-247-3283-2 22. A. Alexander. ed. Foliar Fertilization. 1986. ISBN 90-247-3288-3. Fundamental, Ecological and Agricultural Aspects of Nitrogen Metabolism in Higher Plants Proceedings of a symposium organized by the Department of Plant Physiology, University of Groningen and the Institute for Soil Fertility, Haren, 9 - 12 April 1985 Edited by H. LAMBERS Department of Plant Ecology University of Utrecht Utrecht, The Netherlands J.J. NEETESON Institute for Soil Fertility Haren, The Netherlands and I. STULEN Department of Plant Physiology University of Groningen Haren, The Netherlands 1986 MARTINUS NIJHOFF PUBLISHERS a member of the KLUWER ACADEMIC PUBLISHERS GROUP DORDRECHT / BOSTON / LANCASTER RINIE HOFSTRA Distributors jar the United States and Canada: Kluwer Academic Publishers, 190 Old Derby Street, Hingham, MA 02043, USA jar the UK and Ireland: Kluwer Academic Publishers, MTP Press Limited, Falcon House, Queen Square, Lancaster LAI lRN, UK jar all other countries: Kluwer Academic Publishers Group, Distribution Center, P.O. Box 322, 3300 AH Dordrecht, The Netherlands Library of Congress Cataloging in Publication Data Fundamental, ecological, and agricultural aspects of n~trogen metabolism in higher 91ancs. (Developments in plant and soil sCiences; v. 19) 1. Nitrogen--Metabolism--Congresses. 2. Plants-- Metabolism--Congresses. 3. Plants, Effect of nitrogen on--Congresses. 4. Ni tro'Jen--Congresses. 5. Cdrbon--~etabolJ.sm--Congresses. I. Lambers, H. II. Neeteson, J. J. III. Stulen, 1. IV. Rijksuniversiteit te Groningen. Vakgroe~ Plantenfysiologie. V. Instituut vocr Bodemvrucht.bddche1d (Netherlands) VI. '1'1 tle: Nitrogen metabolism in hl.gher plants. VII. Series. QK898. N6F86 1986 589.9' 5Q4.· 33 85-25893 ISBN-13: 978-94-010-8437-6 e-ISBN-13: 978-94-009-4356-8 001: 10.1007/978-94-009-4356-8 Copyright © 1986 by Martinus Nijhoff Publishers, Dordrecht. Reprint of the original edition 1986 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publishers, Martinus Nijhoff Publishers, P.O. Box 163, 3300 AD Dordrccht, The Netherlands. Preface Rinie Hofstra has been a member of the Department of Plant Physiology, University of Groningen, the Netherlands, for 24 years. The nearer we came to 31 March 1985, her 65th birthday, the more we all realized how we would miss her - not only scientifically, but also socially. She left her mark on both research and teaching, always with an open mind and willing to change. After her PhD Thesis on 'Nitrogen Metabolism in Tomato Plants' she first continued working in that field, but soon started a joint project with the Department of Plant Ecology on hemiparasites. She then became involved in carbon metabolism, which resulted in her giving a Biotrop Course on C /C metabolism in 3 4 Indonesia. Her own research group, originally working on 'Nitrogen Metabolism', soon embraced 'Energy and Nitrogen Metabolism', as the research on respiration became more and more important. In running her group she showed all sides of her person. She used to stimulate and encourage everyone around her and to integrate the various lines of research. At the same time she always had an open mind for the opinion of all members of her group. And together they regularly criticized and evaluated the various projects and decided how to continue. During those 24 years, plant physiology changed rapidly, but she managed to keep abreast of the latest developments. Both projects she started last dealt with applied aspects of plant physiology. She kept the general view, not only of plant physiology, but of botany as a whole. To honour Rinie Hofstra the Department of Plant Physiology in cooperation with the Institute for Soil Fertility organized a Symposium on Nitrogen Metabolism in Higher Plants, in which Fundamental, Ecological and Agricultural Aspects were included. This book contains the Proceedings of that Symposium, which was held in Haren, the Netherlands, from 9 to 12 April 1985. According to many participants the Symposium was 'both scientifically interesting and sociably stimulating'. Precisely her spirit! Let the Proceedings of this Symposium pay a just tribute to her. Haren, July 1985 HANSLAMBERS JACQUES NEETESON INEKE STU LEN Editors vii Foreword Small talk from a senescent lady More than a year ago, I suggested organizing a workshop on nitrogen and carbon metabolism to my coworkers Ineke Stulen and Hans Lambers, but, to my astonishment, they were not at all enthusiastic. Was it not a good idea? Some time later I mentioned it again and then they had to tell me that they were already preparing a symposium on nitrogen metabolism for the year of my retirement in cooperation with the Institute for Soil Fertility. At first I was a little bit angry at the thought of so much attention being given to my retirement. Never theless, I had to concede because preparations were in progress and in hindsight, I am very glad of their initiative and I would like to thank them for spending so much time and taking the trouble in organizing the symposium. Two points gave the symposium a very special value for me: Firstly, that it was a joint venture of the Department of Plant Physiology and the Institute for Soil Fertility; and secondly, that the organizing com mittee decided to make the whole plant the centre of interest. To explain the first point, about the joint venture, we have to go back 25 years, when I began my PhD research. You may wonder: 'Twenty five years ago? You were a slow starter!' And indeed, I was. In my former life, I worked for years as an analytical technician on food control and medical analysis. These years were fruitful in more than one way. I liked my work in the lab. It was applied and useful, and I had a lot of time to spare for all sorts of other things. But then I discovered that I fell into a routine in my daily work: that was after having examined thousands of samples of blood, milk, bread, marmelade, etc. I wanted more and the research I did, I could not finish, due to lack of knowledge. I decided to make a new start at the University. To benefit from earlier studies, my choice was between pharmacy, chemistry and biology. Biology was out because of experiments on viii FOREWORD ix animals, not because of ethical considerations but simply because I disliked handling animals, and I was advised not to study chemistry because of bad prospectives for a job. Pharmacy was not altogether a negative choice as the degree included courses in plant physiology and plant taxonomy and botany was one of my special interests. Moreover, courses in pharmacy gave much information about plants from all over the world. I soon discovered that it was like being back at school, with hardly a chance of doing real research! I was, however, very much stimulated by the lectures in plant physiology which were given by the late Professor Arisz, a well-known ion-uptake physiologist. He even treated us, first-year students as grown-up scientists and gave me a real interest in plant physiology, so I decided to spend the final six-months course for research in the Department of Plant Physiology. By then Professor Van Raalte had succeeded Professor Arisz. He had a broad interest and suggested that I would study amino acids in the bleeding sap of plants. At the end of my pharmacy degree, I could choose - remarkably as it may seem now - between different jobs: a teaching position in analytical chemistry at the Technological University in Delft, or at the Department of Pharmacotherapy in Groningen, or obtaining a PhD at the Department of Plant Physiology. Or, I could have opened a pharmacy. I decided to get a PhD in plant physiology. Professor Van Raalte may have thought he would obtain a valuable analytical chemist, but I think that I often disappointed him deeply. One piece of advice he gave me was to read detective thrillers: it stimulates the flexibility in scientific thinking. I still find this very god'd- advice. Beginning my research in 1962, I studied the influence of light and temperature, of nitrogen source and of flowering and fruiting on amino acids in the bleeding sap of the tomato plant. The sixties in the Netherlands were, as Wareing described them for Great Britain: 'Years of unprecedented university expansion, easy to get appointments and grants'. The Department of Taxonomy and Anatomy and that of Physiology and Cytology were all housed together in the Botanical Laboratory, an old building in the old centre of Groningen, with a beautiful botanical garden. Despite being in the same building, there was almost no scientific cooperation and even in plant physiology, with seven PhD students, the research themes were quite diverse: on hormones, on ion transport, on effects of low temperature and anaerobic root conditions; and myself on nitrogen metabolism. The Department of Plant Physiology originally gave courses in cytology and microbiology, but in those days of expansion a new Department of Microbiology as well as a new Department of Plant x FOREWORD Ecology were created. A new Department of Biochemistry took its residence in the Faculty of Chemistry, and in Biology another department, that of Developmental Biology, emerged. The first plans were made for a new building in which all biological departments could be brought together. The different groups grew more and more apart. Sometimes a bridge was built such as between plant physiology and ecology in the research on hemiparasites, but this was created more by personal contacts than by scientific interactions. This period, blissful in expansion and in possibility for students, alas, lasted only about ten years. It closed as the energy crisis gave way to a financial crisis. Money became scarce and now we are back in the ice age, as universities reduce their expenses, cut staff numbers, and students have difficulties in finding jo bs. Despite these troubled times, I can also see a positive side in this period. Scientists from diverse disciplines are being forced to cooperate and projects are being tackled simultaneously from different angles. This is important as we often have the blinkered view that all problems can be solved by research in our own specific field. Let me give some examples. The situation often arose such as was described to me by an ecologist in 1971, at a conference on 'Living in Extreme Conditions' in Yugoslavia. In a discussion with a plant physiologist he discovered that: 'That man intended to work on a certain species, and he did not even know that we already grew it in our greenhouse'. That was often the situation. But this lack of cooperation could change! In 1970 I inves tigated the occurrence of C plants in different environments in 4 Indonesia, with a group of south-east Asian scientists, in which an anatomist, a taxonomist, a forester, an ecologist and plant physiologists worked together. The C syndrome is an excellent problem in the field 4 of Botany as could be seen in the reports of the symposium, held in 1970 in Australia, where it is obvious what could be achieved by cooperation. Even in the narrow field of plant physiology, we fell into the trap of thinking that the occurrence of plants in nitrogen-rich and nitrogen-poor conditions could be understood with a proper under standing of the nitrogen metabolism. However, an investigation of two subspecies of Hypochaeris radicata showed that the shoot to root ratio rather than aspects of nitrogen metabolism, explains the occur rence in nitrogen-rich and nitrogen-poor habitats. Similarly a study on the hemiparasitic Rhinanthus showed that it benefitted more from water, transported from host to parasite after attachment, than from nitrogen. Recent studies on CO -enrichment pointed again to 2 morphological differences brought about by enrichment of CO in the 2 atmosphere. FOREWORD xi Approaching a problem from several disciplines and cooperation in research is very important but sometimes difficult. Scientists are very individual, considering themselves as the most important in their field of research. Whereas cooperation requires a more egalitarian attitude. To explain my second point about this symposium - the focus on the whole plant - we need to go back to the sixties. In those days, it was quite normal to work with very small parts of a plant, such as leaf discs, coleoptiles or root pieces. Important as this type of work may have been, it is my firm belief that it cannot provide us with a full understanding of the physiological processes in the intact plant as, e.g., changes in metabolism due to transport from one part of the plant to another. Gradually the whole plant has come into focus again. In our own group, Hans Lambers has worked on energy metabolism for some time, which made it possible for us to investigate aspects of both energy and nitrogen metabolism in the whole plant. In these proceedings various groups report on interactions between carbon or energy and nitrogen metabolism, on distribution and redistribution of carbon and nitrogen. In the last two decades or so, we have also come to realize that observations made on one species are not necessarily valid for all. Costermans, a taxonomist in Bogor, Indonesia, brought this home to me in our discussions on C metabolism: 'First you plant physiologists 4 stated that the first step of CO fixation is by the enzyme ribulose 2 bisphosphate carboxylase. Now you tell us about PEP-carboxylase being involved in this first step, at least in some plants. What will you tell us next year?' There are metabolic processes that occur in the same way in all plant species, whereas others do not and we must be very careful not to generalize our data to include all plant species. This you will find out in these proceedings: there are differences in the dis tribution of nitrate reductase over shoot and roots, in preference for the nitrogen source and in the major carbon storage compounds. Looking back over 25 years of being a plant physiologist, I noted in the first period a more intense specialization with a tendency to lose sight of the whole plant. The development in the seventies was in many respects a good one. More appreciation for each other's work, more cooperation and a greater emphasis on the whole plant again. Moreover, our eyes have been opened to environmental problems. Now government and industry promote specific aspects of research. Major problems like air pollution, over-manuring, salt and low temperature tolerance need applied research. To prevent or solve these problems, research of an applied nature is needed, e.g. by institutes on soil science and on plant breeding. But the problems also need a