Louisiana State University LSU Digital Commons LSU Historical Dissertations and Theses Graduate School 1992 Shoot Growth and Form of Senna Obtusifolia in Response to Soybean and Intraspecific Competition. James Edward Smith Louisiana State University and Agricultural & Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses Recommended Citation Smith, James Edward, "Shoot Growth and Form of Senna Obtusifolia in Response to Soybean and Intraspecific ompeC tition." (1992). LSU Historical Dissertations and Theses. 5357. https://digitalcommons.lsu.edu/gradschool_disstheses/5357 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. University Microfilms International A Bell & Howell Information Company 300 North Zeeb Road. Ann Arbor. Ml 48106-1346 USA 313/761-4700 800/521-0600 Order Number 9301105 Shoot growth and form of Senna obtusifolia in response to soybean and intraspecific competition Smith, James Edward, Ph.D. The Louisiana State University and Agricultural and Mechanical Col., 1992 UMI 300 N. ZeebRd. Ann Arbor, MI 48106 SHOOT GROWTH AND FORM OF SENNA OBTUSIFOLIA IN RESPONSE TO SOYBEAN AND INTRASPECIFIC COMPETITION A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Plant Pathology and Crop Physiology by James E. Smith B.A., Rice University, 1982 M.S., Louisiana State University, 1985 May 1992 Acknowledgments This research and dissertation were made possible largely through the love and support of my family, particularly my parents Patricia and Roland as well as Marsha and Emily (I hope her college career will be shorter than mine has been). The contributions made by my advisor, Peter Jordan, have been invaluable. I am very appreciative of his insight in the world of biology provided through numerous discussions of topics variously related to biology. I also thank my friends in weed biology, plant physiology, and botany as well as my committee members for their contributions. Table of Contents page ACKNOWLEDGMENTS ........................................................................................................... ii LIST OF TABLES .......................................................................................................................... iv LIST OF FIGURES ....................................................................................................................... v LIST OF ABBREVIATIONS ..................................................................................................... vi ABSTRACT ................................................................................................................................ vii CHAPTERS 1 INTRODUCTION .......................................................................................................... 1 2 SHOOT STRUCTURE AS AFFECTED BY SOYBEAN INTERFERENCE ....................................................................... 14 3 NEAREST NEIGHBOR EFFECTS ON GROWTH AND SHOOT FORM ...................................................................................... 33 4 STAND DENSITY EFFECTS ON LIGHT INTERCEPTION ........................ 62 5 CONCLUSIONS ............................................................................................................. 77 LITERATURE CITED ................................................................................................................. 79 APPENDIX: ADDITIONAL TABLES AND FIGURES .................................................... 85 VITA 101 iii List of Tables table page 2.1 Height and dry weight of soybean canopy......................................................... 21 2.2 Components of shoot structure and dry weight of sicklepod added to soybean 24 2.3 Significance of treatment effects for sicklepod added to soybean ............... 26 2.4 Correlation of shoot structure and dry weight for sicklepod added to soybean 28 3.1 Sicklepod shoot dry weight, canopy dry weight, and leaf area index . 45 3.2 Correlation of shoot structure and dry weight for sicklepod at 76 DAE 45 3.3 Number of branches formed and branch survival on sicklepod shoots . 48 3.4 Branch characteristics from one-third of height segments along the main-stem 49 3.5 Shoot and branch dry weight of sicklepod adjacent to a gap in the stand . 54 3.6 Laterally incident R:FR at top of sicklepod adjacent to a gap in the stand 54 4.1 Leaf area index and node index of sicklepod stan d s................................ 68 4.2 Individual leaf area and petiole length of sicklepod ....................................... 68 4.3 Coefficients of light interception for sicklepod stands.................................... 75 A .l Number and dry weight of leaves of sicklepod added to soybean ............ 86 A.2 Dry weight of soybean canopy adjacent to widely spaced sicklepod .... 87 A.3 Correlation of shoot structure and dry weight for sicklepod at 20 and 36 DAE 88 A .4 Shoot dry weight and height of nearest neighbors for sicklepod in monoculture 89 A.5 Number of branches and branch dry weight of widely spaced sicklepod . 89 A .6 Characteristics of branches of sicklepod adjacent to a gap in the stand . 90 iv List of Figures figure page 2.1 Growth of sicklepod in stands added to soybean ............................................... 22 2.2 Distribution of height of leaves and branches on sicklepod added to soybean 30 3.1 Growth of sicklepod in monoculture stands ........................................................ 41 3.2 R:FR, rate of elongation, and final internode length at sicklepod shoot apex 43 3.3 Profiles of vertical and lateral position of leaf-bearing nodes on sicklepod 47 3.4 Early shape and growth of sicklepod branches at lower main-stem nodes 52 4.1 Vertical distribution of leaf area index in sicklepod canopies ...................... 69 4.2 Vertical distribution o f leaf-bearing nodes in sicklepod canopies ................. 70 4.3 Frequency distribution of sicklepod leaf cosine of angle of incidence . 72 A.l Site weather information, 1988 91 A.2 Site weather information, 1989 92 A.3 Site weather information, 1990 93 A.4 Diagram for typical plot of sicklepod stands added to soybean ................... 94 A.5 Diagram for typical plot of widely spaced sicklepod added to soybean . 95 A.6 Diagram for typical plot of sicklepod monoculture stands...... ........................... 96 A.7 Diagram for typical plot of sicklepod adjacent to a gap in the stand .... 97 A.8 Distribution of branch azimuths at 36 DAE for sicklepod monocultures, 1989 98 A.9 Distribution of branch azimuths at 36 DAE for sicklepod monocultures, 1990 99 A. 10 Distribution of branch azimuths at 33 DAE for sicklepod adjacent to a gap 100 v List of Abbreviations abbreviation ai active ingredient cos[i] cosine of angle of incidence between direct solar radiation and a line normal to the leaf surface DAE days after emergence DAS days after soybean emergence I flux density of incident radiation IQ flux density of incident radiation measured above the plant canopy K coefficient of light interception by the canopy LAI leaf area index, m2 leaf surface per m2 of ground surface NI node index, number of leaf-bearing nodes per m2 of ground surface R:FR the ratio of quantum flux density of red light (655 to 665 nm) to far-red light (725 to 735 nm) Abstract Effects of competition on growth and formation of shoot structure in sicklepod (Senna obtusifolia’) were examined, with particular emphasis on the effect of nearest neighbors on branching and canopy formation. Sicklepod was established as 1) stands of 26 plants m"2 added to soybean, 2) individuals widely enough spaced to produce only interspecific competition when added to soybean, or 3) regularly spaced monoculture stands with 15, 25, 35, and 50 cm interplant distances. Repeated surveys of individual shoots characterized