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
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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