Plant-Plant Allelopathic Interactions

List of Illustrations; List of Tables; Abbreviations; Dedication; Preface; References; Acknowledgements Chapter 1. Plant-plant Allelopathic Interactions; 1.1 References Chapter 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; 2.4.6 Relationships Between Phenolic Acid-utilizing Microbes and Phenolic Acid Inhibition; 2.4.7 Effects of Seedling-microbe-soil Systems on 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; 2.7References Chapter 3: Plant-plant Allelopathic Interactions. Phase II: Field/Laboratory Experiments; 3.1 Annual Broadleaf Weed Control in No-till Systems; 3.2 Material, 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; 3.4.2 Determine if Soil Extracts could be Used Directly in Laboratory Bioassays for the Detection of Allelopathic Activity; 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; 3.4.4 Characterize Cover Crops and Cover Crop Residues and How These May Potentially Modify the Soil Environment; 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; 3.4.6 Determine the Respective Importance of Shoot and Root Residues in Regulating Early Broadleaf Weed Seedling Emergence; 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; 3.5 Summary of Major Points; 3.5.1 Effects of Cover Crop Residues on Physicochemical and Biotic Environments 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; 3.6 References Chapter 4: Phase III: Summing Up; 4.1 Hypotheses; 4.1.1 Plant-plant Allelopathic Interactions. Phase I: The Laboratory; 4.1.2 Plant-plant Allelopathic Interactions. Phase II: Field/Laboratory; 4.2 Final Comments; 4.2.1 How Likely are the Necessary Phenolic Acid Concentrations and Environmental Conditions 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 Field 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; 4.6 References Author Index; Subject Index