E-Book Content
AD VANCES IN AGRONOMY VOLUME 28 CONTRIBUTORS TO THIS VOLUME RODNEY J. ARKLEY A. v. BARKER JOHN E. BEGG J. M. BREMNER C.M. DONALD L. T. EVANS E. A. N. GREENWOOD J. HAMBLIN R. D . HAUCK D . N . MAYNARD P. L. MINOTTI N. H. PECK G . C.M.SAGE NEILC. TURNER INDRA K.VASIL I. F. WARDLAW ADVANCES IN AGRONOMY Prepared under the Auspices of the AMERICANSOCIETY OF AGRONOMY VOLUME 28 Edited by N. C . BRADY International Rice Research Institute Manila, Philippines ADVISORY BOARD w. L COLVILLE, CHAIRMAN G. W. KUNZE D. G. BAKER D. E WEIBEL G. R DUTT H J. GORZ M, STELLY, EX OFFICIO, ASA Headquarters 1976 ACADEMIC PRESS 0 New York San Francisco London A Subsidiary of Harcourt Brace Jovanovich, Publishers COPYRIGHT 0 I 976,w ACADEMIC PRESS, INC. ALL RIGHTS RESERVED. NO PART O F THIS PUBLICATION MAY BE REPRODUCED OR TRANSMITTED IN A N Y FORM OR BY ANY MEANS, ELECTRONIC O R MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR A N Y INFORMATION STORAGE AND RETRIEVAL SYSTEM, WlTHOUT PERMISSION IN WRITING FROM THE PUBLISHER. ACADEMIC PRESS, INC. 111 Piftb Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. 24/28 Oval Road, London N W l LIBRARY OF CONGRESS CATALOG CARD NUMBER:50-5598 ISBN 0-12-000728-2 PRINTED IN THE UNITED STATES OF AMERICA CONTENTS ............................ PREFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CONTRIBUTORS TO VOLUME 28 ix xi NITROGEN STRESS IN PLANTS E . A. N . Greenwood I . Introduction .......................................... 1 Quantitative Concepts of Nutrient Deficiency . . . . . . . . . . . . . . . . . 2 Nitrogen Stress ........................................ 7 Factors Affecting Nitrogen Stress .......................... 14 Alternative Evaluators of Nitrogen Stress .................... 18 Applications .......................................... 28 Conclusions and Aspirations .............................. 34 References ............................................ 34 I1. 111. IV . V. VI . VII . STATISTICAL METHODS IN SOIL CLASSIFICATION RESEARCH Rodney J . Arkley I . Introduction: Objectives and Problems of Soil Classification ..... I1. Numerical Taxonomy or Cluster Analysis of Soils .............. I11. Ordination of Soils ..................................... IV. Soil as an Anisotropic Entity .............................. V . Statistical Methods for Comparing Classification ............... VI . Conclusions and Evaluation ............................... References ............................................ 37 39 54 59 63 64 68 NITRATE ACCUMULATION IN VEGETABLES D. N . Maynard. A. V. Barker. P . L.Minotti. and N . H .Peck I . Introduction .......................................... 71 I1. Hazards of Nitrate and Nitrite to Human Health ............... 72 I11. Factors Affecting Nitrate Accumulation ..................... 77 IV. Nitrate Concentrations in Vegetables ....................... V . Conclusions ........................................... References ............................................ V 99 113 114 vi CONTENTS THE PROGRESS. PROBLEMS. AND PROSPECTS O F PLANT PROTOPLAST RESEARCH Indra K . Vasil I. I1. 111. IV. V. Introduction .......................................... Isolation of Protoplasts .................................. Culture of Protoplasts ................................... Protoplasts and the Genetic Modification of Plants ............. TheF