Plant–Plant Allelopathic Interactions

Plant–Plant Allelopathic Interactions Udo Blum Plant–Plant Allelopathic Interactions Phenolic Acids, Cover Crops and Weed Emergence 123 Udo Blum Department of Plant Biology North Carolina State University Raleigh, NC 27695-7612 USA [email protected] ISBN 978-94-007-0682-8 e-ISBN 978-94-007-0683-5 DOI 10.1007/978-94-007-0683-5 Springer Dordrecht Heidelberg London New York Library of Congress Control Number: 2011922311 © Springer Science+Business Media B.V. 2011 No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) This book is dedicated to all who have labored and will labor in the field of plant–plant allelopathic interactions. Preface For part of my PhD thesis I characterized the distribution of tannic acids in soils underneath sumac (Rhus copallina L.) located in abandoned fields of central Oklahoma (Blum and Rice 1969). Large quantities of tannic acids were found in the litter and organic residues underneath sumac. Tannic acids, which are very water soluble, were also found in the soil to a depth of 75 cm, with a definite zone of concentration at 45–55 cm. The techniques utilized at the time to recover and quantify tannic acids were rudimentary, at best. Amounts below 400 ppm added to soils could not be recovered, even though concentrations as low as 33 ppm added to soils inhibited nodulation of red kidney beans (Phaseolus vulgaris L. “Burpee”). These observations and their implications to plant–plant allelopathic interactions intrigued me at the time and I made a promise to myself that I would take another look at this subject in the future. Around 1980 I was ready to fulfill that promise. For the next 20 plus years research in my laboratory was primarily focused on various aspects of plant–plant allelopathic interactions with an emphasis on seedling behavior, soil chemistry, and microbiology. This book is a summary and retrospective analysis of this research program. Although research publications on allelopathy have increased at a phenomenal rate since the 1980s, what is generally lacking are in-depth analyses and integration of this literature. For example, a quick search of Science Citation Index yielded 112 publications between 1981 and 1990, 627 publications between 1991 and 2000, and 1,615 publications between 2001 and 2010. The terms “allelopathic interactions” yielded 6, 58, and 212 publications over the same time intervals. However, less than 10% of these 276 citations listed for allelopathic interactions could be classified as review papers for allelopathic interactions of higher plants. These reviews, with minor exceptions, summarized, described, pooled, and/or integrated data for plant–plant allelopathic interactions determined for different species, environments, and ecosystems utilizing a range of different methods/protocols. Such reviews are useful in that they can identify potential/likely mechanisms that may bring about plant–plant allelopathic interactions and provide general guidelines and directions for future research. However, to identify and determine actual mechanisms that control and/or regulate the expression of plant–plant allelopathic interactions within a given ecosystem requires in-depth quantitative analyses of individual ecosystem vii viii Preface processes and their interactions utilizing consistent experimental protocols. The research described in this book is an attempt to do just that for one type of ecosystem. This book does not provide a comprehensive review of the plant–plant allelopathic interaction literature. For a general review of this literature the reader may wish to read several of the following: Rice (1974, 1979, 1983, 1984, 1995), Putnam and Tang (1986), Waller (1987), Siqueria et al. (1991), Inderjit et al. (1995, 1999), Inderjit and Keating (1999), Macías et al. (1999, 2004), Reigosa et al. (2006), Fujii and Hiradate (2007), Willis (2007), and Zeng et al. (2008). There are several things that are unique about this book: a. The general format is that of research papers published in scientific journals. The materials are organized in sections such as, Abstract, Introduction, Materials and Methods, and Results and Discussion. b. There are four chapters, including an introduction to allelopathic plant–plant interactions (Chapter 1). They all emphasize basic aspects of science, but Chapter 2 is more theoretical/hypothetical in nature, Chapter 3 is more practical in nature, and Chapter 4 integrates the information presented in Chapters 2 and 3 and suggests future direction for research in plant–plant allelopathic interactions. c. Comments regarding logic, reasons, and justifications, for various procedures used are provided throughout the book. d. The Scientific Method and its approach to research are emphasized. For example, instead of definitive conclusions at the end of the book cons and pros are provided so that readers can draw their own conclusions. The reader will also find an extended listing of if-then hypotheses, and e. Although a broad range of literature is included, the primary focus of this book is a summary and retrospective analysis of some 20 plus years of research on plant–plant allelopathic interactions at North Carolina State University. The above format was chosen so that researchers, students, farmers, as well as layman interested in science, reduced tillage production, and plant–plant allelopathic interactions, in particular, can learn to appreciate and understand the nature of science, its benefits and limitations, and our present knowledge of the action of natural products such as phenolic acids in soil on plant growth and development. Raleigh, NC August 19, 2010 Udo Blum References Blum U, Rice EL (1969) Inhibition of symbiotic nitrogen-fixation by gallic and tannic acid and possible roles in old-field succession. Torrey Bot Club 96:531–544 Fujii Y, Hiradate S (2007) Allelopathy: new concepts and methodology. Science Publishers, Enfield, NY Inderjit, Keating KI (1999) Allelopathy: principles, procedures, processes, and promises for biological control. Adv Agro 67:141–231 Preface ix Inderjit, Daskshini KMM, Einhellig FA (1995) Allelopathy: organisms, processes, and applications. ACS symposium series, vol 582. American Chemical Society, Washington, DC Inderjit, Daskshini KMM, Foy CL (1999) Principles and practices in plant ecology: allelochemical interactions. CRC Press, Boca Raton, FL Macías FA, Galindo JGC, Molinillo JMG, Cutler H (1999) Recent advances in allelopathy I. A science for the future. Cádiz University Press, Puerto Real Cádiz, Spain Macías FA, Galindo JGC, Molinillo JMG, Cutler H (2004) Allelopathy: chemistry & modes of action of allelochemicals. CRC Press, Boca Raton, FL Putnam AR, Tang CS (1986) Science of allelopathy. Wiley, New York, NY Reigosa MJ, Pedrol N, Gonzalez L (2006) Allelopathy. A physiological process with ecological implications. Springer, Dordrecht, The Netherlands Rice EL (1974) Allelopathy. Academic Press, Orlando, FL Rice EL (1979) Allelopathy – an update. Bot Rev 45:15–109 Rice EL (1983) Pest control with nature’s chemicals: allelochemics and pheromones in gardening and agriculture. University of Oklahoma Press, Norman, NY Rice EL (1984) Allelopathy. Academic Press, Orlando, FL Rice EL (1995) Biological control of weeds and plant diseases: advances in applied allelopathy. University of Oklahoma Press, Norman, NY Siqueira JO, Nair MG, Hammerschmidt R, Safir GR (1991) Significance of phenolic compounds in plant-soil-microbial systems. Crit Rev Plant Sci 10:63–121 Waller GR (1987) Allelochemicals: role in agriculture and forestry. ACS symposium series, vol 330. American Chemical Society, Washington, DC Willis RJ (2007) The history of allelopathy. Springer, Dordrecht, The Netherlands Zeng RS, Mallik AU, Luo SM (2008) Allelopathy in sustainable agriculture and forestry. Springer, New York, NY Acknowledgements Although my research interests in allelopathy have been a primary focus for most of my academic career, I did take several excursions into other research areas (e.g., air pollution biology, and salt marsh ecology) before returning full time to the subject matter of allelopathy. In retrospect these excursion turned out to be extremely beneficial to my understanding of stress physiology and ecosystem biology, important insights needed when studying plant–plant allelopathic interactions. My teaching of beginning and advanced undergraduate botany courses and graduate courses in plant physiology, ecology, plant physiological ecology, and root ecology also proved to be invaluable in my pursuit of understanding the mechanisms of plant–plant allelopathic interactions by providing me with an opportunity to develop a much more in-depth appreciation of plant morphology, anatomy, physiology, and population biology, and soil physics, chemistry and microbiology. Equally as important as a solid understanding of plant, microbial, and soil biology was an appreciation of the scientific method. The importance of the scientific method as a tool for studying biological systems was instilled within me by EL Rice, my PhD mentor at The University of Oklahoma, and was reinforced by my teaching of botany courses using the Socratic Method at both the University of Oklahoma and at North Carolina State University. I also want to acknowledge the help of several statisticians at North Carolina State University who over the years provided me with the opportunity to develop and refine my skills in experimental design, data analysis, and modeling. In particular, I would like to express my appreciation to Professors RJ Monroe, JO Rawlings, and TM Gerig of the Department of Statistics. Along the way there were numerous faculty members, graduate and undergraduate students, and technicians who influenced, shaped, and reshaped my research program in allelopathy. A deep felt thank you to all of them. In particular, I would like to express my appreciation to faculty members C Brownie, RC Fites, TM Gerig, F Louws, LD King, SR Shafer, SB Weed, TR Wentworth, and AD Worsham, visiting scientist S-W Lyu, technicians/graduate students BR Dalton and K Klein, graduate students MF Austin, CL Bergmark, FL Booker, LJ Flint, AB Hall, LD Holappa, M Kochhar, ME Lehman, JV Perino, KJ Pue, J Rebbeck, JR Shann, K Staman, ER Waters, and AG White, and the assistance of CG Van Dyke in processing the xi xii Acknowledgements samples and taking the electron micrographs of microbial populations on cucumber root surfaces. I would also like to acknowledge the following organizations for providing research support and/or funding: North Carolina Agricultural Research Service, USDA Competitive Research Grants Program, Southern Region Low-Input Agricultural Systems Research and Extension Program, North Carolina Agricultural Foundation Graduate Research Assistantship Program, and the Departments of Botany (now Plant Biology), Soil Science, and Statistics. Finally, the author wishes to thank MA Blum, SO Duke, JR Troyer, JD Weidenhamer, and AD Worsham for editing, reviewing, and for thoughtful and constructive comments. Contents 1 Plant–Plant Allelopathic Interactions . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Plant–Plant Allelopathic Interactions. Phase I: The Laboratory . 2.1 Criteria for Model Systems . . . . . . . . . . . . . . . . . . . 2.2 Materials, Methods, and Commentary . . . . . . . . . . . . . 2.2.1 General Bioassay Procedures . . . . . . . . . . . . . . 2.2.2 Bioassay Species . . . . . . . . . . . . . . . . . . . . 2.2.3 Soil Substrates . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Seedling Containers . . . . . . . . . . . . . . . . . . . 2.2.5 Sorption and Microbial Utilization Studies . . . . . . . 2.2.6 Phenolic Acids . . . . . . . . . . . . . . . . . . . . . 2.2.7 Phenolic Acid Solutions . . . . . . . . . . . . . . . . . 2.2.8 Solution Additions to Seedling Systems . . . . . . . . 2.2.9 Phenolic Acid Extraction Procedures . . . . . . . . . . 2.2.10 Quantification of Individual Phenolic Acids . . . . . . 2.2.11 Rhizosphere and Soil Microbial Populations . . . . . . 2.2.12 Measurements . . . . . . . . . . . . . . . . . . . . . . 2.2.13 Data Analyses . . . . . . . . . . . . . . . . . . . . . . 2.3 Research Objectives . . . . . . . . . . . . . . . . . . . . . . . 2.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . 2.4.1 Effects and Duration of Effects of Phenolic Acids on Seedlings in Nutrient Culture . . . . . . . . . . . . 2.4.2 Effects of Seedlings, Mixtures of Phenolic Acids, and Microbes on Phenolic Acid Concentrations in Nutrient Culture . . . . . . . . . . . . . . . . . . . 2.4.3 Interactions of Phenolic Acids with Sterile and Non-sterile Soils . . . . . . . . . . . . . . . . . . 2.4.4 Effects of Phenolic Acids on Bulk-Soil and Rhizosphere-Microbial Populations . . . . . . . . 2.4.5 Effects and Duration of Effects of Phenolic Acids on Seedlings in Soil Culture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 . . . . . . . . . . . . . . . . . . 9 10 11 12 14 14 16 18 18 19 20 22 24 25 26 29 30 31 . . 31 . . 37 . . 41 . . 50 . . 54 xiii xiv Contents 2.4.6 Relationships Between Phenolic Acid-Utilizing Microbes and Phenolic Acid Inhibition . . . . . . . 2.4.7 Effects of Seedling-Microbe-Soil Systems on the Available Concentrations of Phenolic Acids in Soil Solutions . . . . . . . . . . . . . . . . . . . 2.4.8 Comparison of the Effects of Phenolic Acids on Seedlings in Nutrient and Soil Culture . . . . . 2.4.9 Effects of Phenolic Acids at Various Life Stages . . 2.5 Summary of Major Points for Model Systems . . . . . . . 2.5.1 Seedlings . . . . . . . . . . . . . . . . . . . . . . 2.5.2 Microbes . . . . . . . . . . . . . . . . . . . . . . 2.5.3 Phenolic Acids . . . . . . . . . . . . . . . . . . . 2.6 Relevance of Model Systems to Field Studies . . . . . . . 2.6.1 Promoters, Modifiers, and Inhibitors . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 . . . . 60 . . . . . . . . . 3 Plant–Plant Allelopathic Interaction. Phase II: Field/Laboratory Experiments . . . . . . . . . . . . . . . . . . 3.1 Annual Broadleaf Weed Control in No-Till Systems . . . . . 3.2 Materials, Methods, and Commentary . . . . . . . . . . . . 3.2.1 Soil and Plant Tissue/Residue Analyses . . . . . . . 3.2.2 Laboratory Bioassays . . . . . . . . . . . . . . . . . 3.2.3 Field Studies . . . . . . . . . . . . . . . . . . . . . 3.2.4 Data Analyses . . . . . . . . . . . . . . . . . . . . . 3.3 Research Objectives . . . . . . . . . . . . . . . . . . . . . . 3.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . 3.4.1 Characterize the Phenolic Acids in Soils of No-Till and Conventional-Till Systems and to Establish Correlations Between Easily Obtained Soil Characteristics and Phenolic Acids in Soils (Blum et al. (1991); Plenum Publishing Corporation, Excerpts Used with Permission of Springer Science and Business Media) . . . . . . . . 3.4.2 Determine if Soil Extracts could be Used Directly in Laboratory Bioassays for the Detection of Allelopathic Activity (Blum et al. (1992); Plenum Publishing Corporation, Excerpts Used with Permission of Springer Science and Business Media) 3.4.3 Characterize How Cover Crop Residues in No-till Systems Affect Early Emergence of Broadleaf Weeds and to Establish and Characterize Potential Relationships Between Early Broadleaf Weed Seedling Emergence and the Physical and Chemical Environments Resulting from the Presence of Cover Crop Residues (Blum et al. (1997); Henry A Wallace Institute for Alternative . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 64 65 65 66 67 70 74 75 . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 86 87 87 90 92 97 97 98 . . . 98 . . . 107 Contents xv Agriculture Inc, Summarized with Permission of Cambridge University Press) . . . . . . . . . . . 3.4.4 Characterize Cover Crops and Cover Crop Residues and How These May Potentially Modify the Soil Environment (Blum et al. (1997); Henry A Wallace Institute for Alternative Agriculture Inc, Summarized with Permission of Cambridge University Press) . . . . . . . . . . . . . . . . . . 3.4.5 Determine Under Controlled Conditions How Effects of Shoot Cover Crop Residues Taken from the Field Change with Time After Desiccation and How Such Effects Are Modified By Temperature, Moisture, and Nitrogen Levels (Lehman and Blum (1997); Summarized with Permission of International Allelopathy Foundation) . . . . . . 3.4.6 Determine the Respective Importance of Shoot and Root Residues in Regulating Early Broadleaf Weed Seedling Emergence (Blum et al. (2002); Summarized with Permission of International Allelopathy Foundation) . . . . . . . . . . . . . . 3.4.7 Determine Under Controlled Conditions How Phenolic Acids-Containing Plant Tissues/Residues Mixed into Soil Modify Phenolic Acid-Utilizing Bulk-Soil and Rhizosphere Microbial Populations (Staman et al. (2001); Plenum Publishing Corporation, Excerpts Used with Permission of Springer Science and Business Media) . . . . . 3.5 Summary of Major Points . . . . . . . . . . . . . . . . . . 3.5.1 Effects of Cover Crop Residues on the Physicochemical Environment of the Soil . . . . . 3.5.2 Phenolic Acids in Cecil Soils . . . . . . . . . . . . 3.5.3 Bioassays of Soil Extracts . . . . . . . . . . . . . . 3.5.4 Field Residue Bioassays: Seedling Emergence . . . 3.5.5 Laboratory Bioassays: Seedlings and Microbes . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Phase III: Summing Up . . . . . . . . . . . . . . . . . . . 4.1 Hypotheses . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Plant–Plant Allelopathic Interaction. Phase I: The Laboratory . . . . . . . . . . . . . . . . . 4.1.2 Plant–Plant Allelopathic Interactions Phase II: Field/Laboratory Experiments . . . . . . . . . 4.2 Final Comments . . . . . . . . . . . . . . . . . . . . . 4.2.1 How Likely Are the Necessary Phenolic Acid Concentrations and Environmental Conditions . . . . 111 . . . . 116 . . . . 123 . . . . 128 . . . . . . . . 133 135 . . . . . . . . . . . . 135 136 138 139 141 143 . . . . . . . . . . . . 151 151 . . . . . . 153 . . . . . . . . . . . . 160 167 . . . . . . . . . . . . xvi Contents Present in Wheat No-Till Crop Systems for Inhibition of Broadleaf Weed Seedling Emergence to Occur? . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Do Phenolic Acids Have a Dominant Role in Regulating Broadleaf Weed Seedling Emergence or Are Phenolic Acids Just One Component of a Larger Promoter/Modifier/ Inhibitor Complex that Regulates Broadleaf Weed Seedling Emergence in Wheat No-Till Crop Systems? 4.3 The Present Paradigm . . . . . . . . . . . . . . . . . . . . . 4.3.1 Phenolic Acids in Soils: Soil Extractions and Dose Response . . . . . . . . . . . . . . . . . . 4.4 A Modified Paradigm . . . . . . . . . . . . . . . . . . . . . 4.4.1 Criteria for Plant–Plant Allelopathic Interactions: An Update . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Potential Tools . . . . . . . . . . . . . . . . . . . . 4.5 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 . . . . . . 174 176 . . . . . . 177 179 . . . . . . . . 180 181 184 185 Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 . . . . Abbreviations ACT CAF C-clover CFU C/N DBW3 DTPA EDTA FER GUE GLM GLU HPLC kv MEOH MES mOsm NLIN OMe PEG PPFD PCO PDMS POH PRO PVP RCM-100 R R+S Basal medium for actinomycetes Caffeic acid Crimson clover Colony-forming units Carbon/nitrogen ratio EDTA extraction of soil at room temperature and soil extraction ratio of 1:100 Diethylenetriaminepentaacetic acid Ethylenediaminetetraacetic acid Ferulic acid Sodium hydroxide extraction of soil at room temperature and soil extraction ratio of 1:1 (GUE2) or at 121◦ C and soil extraction ratio of 1:43 (GUEN) General linear model Glucose High performance liquid chromatograph kilovolts Methanol 2-(N-morpholino) ethanesulfonic acid milliosmoles Non linear Methoxy Polyethylene glycol Photosynthetic photon flux density p-Coumaric acid Polydimethylsiloxane p-Hydroxybenzoic acid Protocatechuic acid Polyvinylporrolidone Radical Pak cartridge Root Root plus shoot xvii xviii S S-clover SIN SYR VAN Abbreviations Shoot Subterranean clover Sinapic acid Syringic acid Vanillic acid List of Figures 2.1 2.2 2.3 2.4 2.5 2.6 2.7 A seedling-microbe-soil model system . . . . . . . . . . . . Light banks: a general view, b nutrient culture, c soil cup system, and d continuous-flow system . . . . . . . . . . . . Containers: a Wheaton glass bottles, b split-root systems, c soil cups, and d soil columns . . . . . . . . . . . . . . . . Some common simple plant phenolic acids, cinnamic acid derivatives on the right and benzoic acid derivatives on the left, where H equals hydrogen, OH equals hydroxy, and OMe equals methoxy . . . . . . . . . . . . . . . . . . . . . Changes in net phosphorous uptake (a; r2 = 0.52), net water uptake (b; r2 = 0.19), and absolute growth rates of leaf expansion (b; r2 for FER = 0.76 and PCO = 0.58) of 13–15 day-old cucumber seedlings as the proportion of the root systems in contact with a phenolic acid was increased in nutrient culture, where FER equals 0.5 mM ferulic acid and PCO equals 0.5 mM p-coumaric acid. Figures based on regressions from Lyu and Blum (1990) (a, b) and Lehman et al. (1994) (b). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . . . . . . . . Effects of ferulic acid and initial nutrient solution pH on net phosphorous uptake (a; 22 day old; r2 for pH 5.5 = 0.71, and pH 6.5 = 0.45), absolute growth rates of leaf expansion (b; 16–18 day old; r2 for pH 5.5 = 0.90, pH 6.25 = 0.69, and pH 7.0 = 0.72), and net water utilization (c; 16–18 day old; r2 for pH 5.5 = 0.95, for pH 6.25 = 0.88, and for pH 7.0 = 0.69) of cucumber seedlings. Figures based on regressions and data from Lehman and Blum (1999b) (a) and regressions from Blum et al. (1985b) (b, c). Plenum Publishing Corporation, regressions and data used with permission of Springer Science and Business Media . . . . The effects of pH on the ionic state of a theoretical phenolic acid with a pKa value of 4.5 (a) and estimated pKa values for . . . . 11 . . . . 13 . . . . 17 . . . . 19 . . . . 32 . . . . 33 xix xx cinnamic and benzoic acids (b). Where CAF equals caffeic acid, PCO equals p-coumaric acid, FER equals ferulic acid, SIN equals sinapic acid, POH equals p-hydroxybenzoic acid, SYR equals syringic acid, and VAN equals vanillic acid. A pKa value for caffeic acid was not available. Figure (b) based on data from Blum et al. (1999b). CRC Press LLC, data used with permission of Taylor & Francis Ltd, http://www.tandf.co.uk/journals. Original sources of data: AJ Leo, personal communication, Leo et al. (1971), Nordstrom and Lindberg (1965), Kenttamaa et al. (1970), Connors and Lipari (1976); Glass (1975) . . . . . . . . . . . . . . . . . . 2.8 Change in absolute and relative rates of leaf expansion of 12 day-old cucumber seedlings as p-coumaric acid declines due to root uptake and microbial utilization in nutrient culture in the presence and absence of aeration, and when solutions were not changed or changed every 4 h. Figures reproduced from Blum and Gerig (2005). Figures used with permission of Springer Science and Business Media . . . . 2.9 Electron micrographs (2500× 17 kv) of root surfaces of 13 day-old cucumber seedlings grown in nutrient culture not treated (controls; a, b) or treated 4 times (starting with day 6) every other day with 0.5 mM p-coumaric acid (c, d). Nutrient solutions (pH 5.0) with or without p-coumaric acid were changed every other day. Fine matrix material in micrographs is very likely mucigel generated by root and associated microbes. Micrographs chosen represent the maximum (a, c) and minimum (b, d) differences observed for 8 micrographs taken along the first 10 mm (tip) of the control and p-coumaric acid treated roots. Finally, microbes observed in these micrographs represent all types of microbes, not just microbes that can utilize phenolic acids as a sole carbon source, since phenolic acid utilizers cannot be distinguished by morphology from other carbon utilizers 2.10 Net depletion of phenolic acid by 12 day-old cucumber seedlings grown in a growth chamber (a; r2 = 0.78) and by 14–18 day-old cucumber seedlings grown in a light bank (b; r2 ≥ 0.79), where FER equals ferulic acid and POH equals p-hydroxybenzoic acid. Nutrient solutions were aerated. Initial pH values for nutrient solutions of (a) were 5.5. Initial pH values for (b) varied as indicated. All phenolic acid values were determined after 5 h. a based on regression from Lehman and Blum (1999b) (Plenum Publishing Corporation, regression used with permission of Springer Science and Business Media) and b based on data points of two figures from Shann and Blum (1987a) . . . . . List of Figures . . . . 34 . . . . 36 . . . . 37 . . . . 38 List of Figures 2.11 The net depletion of phenolic acids in the absence or presence of a second phenolic acid at equal-molar concentrations from nutrient solution by 15-day old cucumber seedlings growing in a light bank. Where FER equals ferulic acid, PCO equals p-coumaric acid, and VAN equals vanillic acid and data in (a) are depletion of ferulic acid, b depletion for p-coumaric acid, and c depletion for vanillic acid. Nutrient solutions were not aerated and had an initial pH of 5.5. The absence of standard error bars indicates that the error bars are smaller than the symbols representing the mean. Figures based on data from Lyu et al. (1990). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media . . . . . . . . . . . 2.12 The decline of 0.5 mM p-coumaric acid (a) and the accumulation and decline of initial phenolic acid breakdown products (b) in nutrient solutions (pH 5.0) surrounding roots of 12 day-old cucumber seedlings. Breakdown products are in p-coumaric acid equivalence. Nutrient solutions were aerated or not aerated. Figures reproduced from Blum and Gerig (2005). Figures used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . 2.13 Recovery of ferulic acid by various extraction procedures from sterile soils 90 days after ferulic acid solutions (1,000 mg/kg soil, pH 6.0) were added to soils. Soil-ferulic acid mixtures were stored in the dark at room temperature. LSD0.05 for Cecil A and B and Portsmouth A and B soils were 28.70, 44.15, 40.69, and 28.66, respectively. Meaning of the abbreviations and details for extraction procedures are provided in Table 2.3. Figure based on data from Dalton et al. (1987). Data used with permission of Soil Science Society of America . . . . . . . . . . . . . . . . . . . . . . 2.14 Recovery of ferulic (FER) acid (a; r2 = 0.99) and vanillic (VAN) acid (b; r2 ≥ 0.95) by 0.5 M EDTA (pH 8) or water 42 days after addition of a range of phenolic acid concentrations to sterile Cecil A and B soils. Figures based on regressions from Blum et al. (1994). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . 2.15 Recovery, over time, of ferulic (FER) acid (a; r2 ≥ 0.89) and vanillic (VAN) acid (b) from sterile Cecil A and B soils by 0.25 M EDTA (pH 7) or water. Phenolic acid added at time zero was 2.5 µmol/g soil. Standard error bars for (b) are smaller than the symbol representing the mean. a based on regressions and b based on data points of two figures from Blum et al. (1994). Plenum Publishing Corporation, xxi . . . . 40 . . . . 40 . . . . 42 . . . . 47 xxii 2.16 2.17 2.18 2.19 2.20 2.21 List of Figures regressions and data used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . Amounts of ferulic acid in soil solution, reversibly sorbed and fixed (irreversibly sorbed) in sterile Cecil A (a) and B (b) soils 35 days after addition. Standard error bars for (a) and (b) are smaller than the symbol representing the mean. Figures reproduced from Blum (1998). Plenum Publishing Corporation, figures used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . Utilization of ferulic acid in soil solution and reversibly sorbed to Cecil A (a) and B (b) soils by microbes. Ferulic acid added at time zero was 2 µmol/g soil. Standard error bars for (a) and (b) are smaller than the symbol representing the mean. Figures reproduced from Blum (1998). Plenum Publishing Corporation, figures used with permission of Springer Science and Business Media . . . . . . . . . . . . Percent ferulic acid and vanillic acid reversibly sorbed and fixed (irreversibly sorbed) by sterile Cecil A (a) and B (b) soils over time. Percentages based on 1–3 µmol/g soil added at time zero. Figures based on data from Blum et al. (1999b). CRC Press LLT, data used with permission of Taylor & Francis Ltd, http://www.tandf.co.uk/journals. Original sources of data: Blum (1997, 1998) and Blum et al. (1994) . Response of bacteria (a), fast-growing bacteria (b), and fungi (c) in Portsmouth A and B soils to 0 and 0.5 µmol/g soil ferulic acid applied every other day starting with day 1, where fast-growing bacteria represent colonies that were ≥ 1 mm in diameter after 6 days of incubation. For (a) LSD0.05 = 2.9 × 105 , for (b) LSD0.05 = 2.88 × 105 , and for (c) LSD0.05 = 2.4 × 102 . Figures reproduced from Blum and Shafer (1988) . . . . . . . . . . . . . . . . . . . . . . . . . The effects of multiple treatments of 7- (a) and 4(b) equal-molar phenolic acid mixtures on cucumber seedling rhizosphere bacterial populations that can utilize phenolic acids as sole carbon sources, where CFU equals colony-forming units. Seedlings were grown in Cecil A soil. The 7-phenolic acid mixture was composed of caffeic, p-coumaric, ferulic, p-hydroxybenzoic, sinapic, syringic, and vanillic acids. The 4-phenolic acid mixture was composed of p-coumaric, ferulic, p-hydroxybenzoic, and vanillic acids. Figure based on data from Blum et al. (2000). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media . . . . . . . . . . . . Concentrations for one to a mixture of four phenolic acids required for a 30% inhibition of mean absolute rates of leaf . . . . 47 . . . . 47 . . . . 48 . . . . 48 . . . . 52 . . . . 53 List of Figures 2.22 2.23 2.24 2.25 expansion for 8–18 day old cucumber seedlings growing in Portsmouth B soil. Figure reproduced from Blum (1996). Figure used with permission of Society of Nematologists . . Concentrations of p-coumaric acid and methionine (a), and p-coumaric acid and glucose (b) required to inhibit dry weight of morningglory seedlings growing in Portsmouth B and Cecil B soils, respectively, by 10–50%. Figures adapted/replicated from Blum et al. (1993) (a) and Pue et al. (1995) (b). Plenum Publishing Corporation, figures used with permission of Springer Science and Business Media . . Effects of ferulic acid on absolute growth rates (cm2 /2 days) of cucumber seedlings growing in Portsmouth A soil as modified by pH (a) and corresponding percent inhibition (b) calculated from data in (a). Figures based on data from Blum et al. (1989). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media . . . . Relationships (a) between percent stimulation of rhizosphere bacteria that can utilize phenolic acids as sole carbon sources and percent inhibition of absolute rates of leaf expansion of cucumber seedlings growing in Cecil A soil treated with a 0.6 µmol/g soil 4-equal-molar phenolic acid mixture (a; r2 = 0.50), where CFU equals colony-forming units and the 4-phenolic acid mixture was composed of p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid. The recoveries (b) of “free” and reversibly sorbed p-coumaric acid (PCO) from sterile or non-sterile Cecil B soil in the presence or absence of glucose (GLU). The absence of standard error bars for (b) indicates that the error bars are smaller than the symbols representing the mean. a was based on a regression from Blum et al. (2000) and b was reproduced from Pue et al. (1995). Plenum Publishing Corporation, regression and figure used with permission of Springer Science and Business Media . . . . . . . . . . . . Effects of total phenolic acid composed of a 4-equal-molar mixture of p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid on absolute rates of leaf expansion (cm2 /day; r2 = 0.44) of 12 day-old cucumber seedlings and microbial populations (CFU/g soil; r2 = 0.49) that can utilize phenolic acids as a sole carbon source in Cecil A soil (a). Relationships between phenolic acid-utilizing microbes (CFU, colony-forming units) and percent inhibition of absolute rates of leaf expansion for cucumber seedlings are presented in b. Values for (b) were calculated from values in (a). Figures based on regressions from Blum et al. (2000). xxiii . . . . 55 . . . . 56 . . . . 57 . . . . 58 xxiv Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media . . . . 2.26 Recoveries of p-coumaric acid from the bottom of Cecil A soil columns in the presence of cucumber seedlings and microbes (a), in the absence of microbes and seedlings (b), and in the presence of microbes but absence of seedlings (c). For (a), approximately 25, 50 or 95 µg/ml of p-coumaric acid in 25% Hoagland’s nutrient solution was applied to the columns at a rate of 2–3.5 ml/h. For (b) and (c), 41 and 54 µg/ml, respectively, of p-coumaric acid in different nutrient solution concentrations (0–50%) was applied to columns at the same rate as in (a). Figures reproduced from Blum et al. (1999a). Cádiz Univ Press, Puerto Real. Figures used with permission of Servicio de Publicaciones Universidad De Cádiz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.27 The changes in µmol/g soil p-coumaric acid (a), soil water (g/150 g soil) (b), and mM p-coumaric acid (c) for cup systems with 12–13 day-old cucumber seedlings and Cecil A soil. Systems were treated with 1 µmol/g soil p-coumaric acid and 20 or 25 g water/150 g soil. Absence of error bars indicates that error bars are smaller than the symbols representing the mean. Figures reproduced from Blum and Gerig (2006). Figures used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . 3.1 Frame used to determine location of subplots for weed seeds. Location of subplot for each weed species within each treatment plot was chosen at random. The two outer subplots were not used . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Cover crops before they were desiccated with glyphosate (a): crimson clover (front right), subterranean clover (front left), wheat (back right) and rye (back left; Blum et al. 1997). Wheat plots after they were desiccated with glyphosate (b): shoots cut and uncut and reference plot in the right-hand corner (Blum et al. 2002) . . . . . . . . . . . . . . . . . . . 3.3 Weed seedlings in wheat plots at end of an experimental period: (a) morningglory upper right corner and prickly sida center, and (b) pigweed center and morningglory lower left 3.4 Some common simple plant phenolic acids, cinnamic acid derivatives on the right and benzoic acid derivatives on the left, where H equals hydrogen, OH equals hydroxy, and OMe equals methoxy . . . . . . . . . . . . . . . . . . . . . 3.5 Tannins. Figure reproduced from Khanbabaee and van Ree (2001). Figure used with permission of the Royal Society of Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . List of Figures . . . . 59 . . . . 61 . . . . 62 . . . . 93 . . . . 94 . . . . 96 . . . . 98 . . . . 99 List of Figures Two examples of polymers that contain phenolic acid moieties: (a) model of humic acid and (b) precursors of lignin. Figure (a) reproduced from Stevenson (1982) and (b) from Grabber (2005). Figure (a) and (b) used with permission of John Wiley and Sons, Inc and Crop Science Society of America, respectively . . . . . . . . . . . . . . . Standard curves. Absorbance of caffeic acid (CAF), ferulic 3.7 acid (FER), p-coumaric acid (PCO), p-hydroxybenzoic acid (POH), protocatechuic acid (PRO), sinapic acid (SIN), syringic acid (SYR), and vanillic acid (VAN) after reacting with the Folin & Ciocalteu’s phenol reagent. Figure reproduced from Blum et al. (1991). Plenum Publishing Corporation, figure used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . 3.8 Phenolic acids extracted from wheat stubble, wheat straw from half buried litter bags, and wheat stubble/soybean (no-till) soil. Phenolic acids isolated and quantified were caffeic acid (CAF), ferulic acid (FER), p-coumaric acid (PCO), p-hydroxybenzoic acid (POH), sinapic acid (SIN), syringic acid (SYR), and vanillic acid (VAN). Because p-coumaric acid was so high in comparison to other phenolic acids in wheat residues, data are presented twice, once with p-coumaric acid (a) and once without p-coumaric acid (b). Because phenolic acids were so low in the soil they are also presented in (c). The absence of standard error bars for wheat straw and soil indicates that the error bars are too small to be visible. Figures based on data from Blum et al. (1991, 1992). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media . . 3.9 Phenolic acids extracted from wheat stubble/soybean (no-till), wheat stubble tilled under/soybean (conventional-till), and fallow/soybean (conventional-till) Cecil A soils for 0–2.5 and 0–10 cm soil cores. Phenolic acids isolated and identified were caffeic acid (CAF), ferulic acid (FER), p-coumaric acid (PCO), p-hydroxybenzoic acid (POH), sinapic acid (SIN), syringic acid (SYR), and vanillic acid (VAN). The absence of standard error bars indicates that the error bars are too small to be visible. Figure based on data from Blum et al. (1991). Plenum Publishing Corporation, data used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . . . . . . 3.10 Effects of a 7-phenolic acid solution modeled after phenolic acids found in wheat stubble/soybean (no-till) soil extracts (pH 5) on radicle and hypocotyl lengths of crimson clover as modified by solute potential of PEG (polyethylene glycol; a; r2 = 0.61) and Hoagland’s solution (b; r2 = 0.37) based xxv 3.6 . . . . 100 . . . . 102 . . . . 103 . . . . 105 xxvi 3.11 3.12 3.13 3.14 List of Figures on freezing point depression (mOsm, milliosmoles) of solutions. The 7-phenolic acid mixture was composed of 10% caffeic acid, 9% ferulic acid, 35% p-coumaric acid, 15% p-hydroxybenzoic acid, 4% sinapic acid, 10% syringic acid, and 17% vanillic acid. Figures based on regressions from Blum et al. (1992). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . . . . . . . . Biological activity (slopes for radicle and hypocotyl lengths of crimson clover; r2 = 0.70) from dose response studies (extract dilutions) of individual wheat stubble/soybean (no-till) soil extracts versus total phenolic acid (ferulic acid equivalence), pH, and freezing point depression (mOsm, milliosmoles) of original undiluted soil extracts. The more negative the biological activity the more inhibitory the factor. Figures based on regression from Blum et al. (1992). Plenum Publishing Corporation, regression used with permission of Springer Science and Business Media . . . . . . . . . . . . The number of pigweed seedlings in cover crop and reference plots for the 1993 experimental period in no-till Cecil A soil. Glyphosate desiccation of cover crops occurred on April 29 (a) and May 10 (b). Where C equals crimson, S equals subterranean and reference equals no-cover crop plots. Figures reproduced from Blum et al. (1997). Henry A Wallace Institute for Alternative Agriculture Inc, figures used with permission of Cambridge University Press . . . . Percent change in mean seedling numbers of morningglory (a), pigweed (b), and prickly sida (c) due to presence of desiccated cover crops for the 1992 and 1993 experimental periods in no-till Cecil A soil, where C equals crimson and S equals subterranean. Figures based on data from Blum et al. (1997). Henry A Wallace Institute for Alternative Agriculture Inc, data used with permission of Cambridge University Press . . . . . . . . . . . . . . . . . . . . . . . . Mean total phenolic acid (ferulic acid equivalents) content of 0–2.5 cm Cecil soil samples taken during the 1992 and 1993 growing season for reference plots (no-cover crop) and cover crop plots. In 1992 cover crops were desiccated with glyphosate in April. In 1993 cover crops were desiccated with glyphosate at two time periods (April and May) and living biomass was tilled into plots in May. The absence of standard error bars indicates that the error bars are too small to be visible. Figure based on data from Blum et al. (1997). Henry A Wallace Institute for Alternative Agriculture Inc, data used with permission of Cambridge University Press . . . . . . 109 . . . . 110 . . . . 113 . . . . 114 . . . . 121 List of Figures 3.15 The emergence of pigweed seedlings in Cecil A soil at 4 water levels and 3 day/night temperatures. Figure based on regressions (r2 for 25/21◦ C = 0.57, for 30/26◦ C = 0.88, and for 35/41◦ C = 0.87) from Lehman and Blum (1997). Regressions used with permission of International Allelopathy Foundation . . . . . . . . . . . . . . . . . . . . 3.16 The effects of soil moisture, and wheat and crimson clover cover crop residues on percent pigweed seedling emergence in Cecil A soil, where C equals crimson. Wheat inhibitory, C-clover inhibitory, and C-clover non-inhibitory were collected 2, 1, and 4 months after glyphosate desiccation, respectively. The absence of standard error bars indicates that the error bars are too small to be visible. Figures adapted from Lehman and Blum (1997). Figures used with permission of International Allelopathy Foundation . . . . . 3.17 Average number of morningglory, pigweed, and prickly sida seedlings in no-till Cecil A soil field plots for two experimental periods [(a) 1996 and (b) 1997] with the following 5 treatments: 1. no cover crop (reference), 2. cut wheat shoots on surface (s only), 3. wheat roots left in place but shoots cut and removed (r only), 4. wheat shoots and roots left in place, but shoots cut (s+r cut), and 5. wheat shoots and roots left in place, but shoots not cut (s+r not cut). The absence of standard error bars indicates that the error bars are too small to be visible. Figures based on data from Blum et al. (2002). Data used with permission of International Allelopathy Foundation . . . . . . . . . . . . 3.18 Percent change of morningglory, pigweed, and prickly sida seedlings in no-till Cecil soil field plots for two experimental periods [(a) 1996 and (b) 1997] with the following 4 treatments: 1. cut wheat shoots on surface (s only), 2. wheat roots left in place but shoots cut and removed (r only), 3. wheat shoots and roots left in place, but shoots cut (s+r cut), and 4. wheat shoots and roots left in place, but shoots not cut (s+r not cut). Figures based on data from Fig. 3.17. Original data from Blum et al. (2002). Data used with permission of International Allelopathy Foundation . . . . . . . . . . . . 3.19 Effects of total phenolic acid composed of a 4-equal-molar mixture of p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid on absolute rates of leaf expansion (cm2 /day; r2 = 0.44) of 12 day-old cucumber seedlings and microbial populations (CFU/g soil; r2 = 0.49) that can utilize phenolic acids as a sole carbon source in Cecil A soil (a). Relationships between phenolic acid-utilizing xxvii . . . . 126 . . . . 127 . . . . 129 . . . . 130 xxviii List of Figures microbes (CFU, colony forming units) and percent inhibition of absolute rates of leaf expansion for cucumber seedlings are presented in (b). Values for (b) were calculated from (a). Figures based on regressions from Blum et al. (2000). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media . . . . . . . . 3.20 Effects of wheat shoot (a; r2 ranged from 0.54 to 0.80) and sunflower leaf (b; r2 ranged from 0.55 to 0.77) tissues incorporated into Cecil A soil on percent inhibition of absolute rates of leaf expansion of cucumber seedlings over time. Figures based on regressions from Staman et al. (2001). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media . . . . . . 3.21 Effects of wheat shoot (a) and sunflower leaf (b) tissues, a phenolic acid mixture composed of equalmolar concentrations of p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid (a, b; r2 = 0.83), or chlorogenic acid (b) supplied to Cecil A soil on rhizosphere phenolic acid-utilizing microbes, where CFU equals colony forming units. The phenolic acid mixture and the chlorogenic acid were applied every other day to the soil while the shoot and leaf tissues were added to the soil only once, at the beginning of the experiment. Sunflower tissues and chlorogenic acid were incorporated and supplied, respectively, to a batch of autoclaved soil. This autoclaved soil, however, was not sterile. Soils were autoclaved only once to reduce the initial microbial populations. Asterisks indicate significant difference from the control (alpha = 0.05). Figures based on data and regressions from Staman et al. (2001). Plenum Publishing Corporation, data and regressions used with permission of Springer Science and Business Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 135 136 List of Tables 2.1 Soil characteristics of Cecil, Portsmouth, and White Store soils . . . . 2.2 Hoagland’s nutrient solution . . . . . . . . . . . . . . . . . . . . . . 2.3 Details for extraction procedures for Fig. 2.13 . . . . . . . . . . . . . 15 16 43 xxix