Literature Review
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Ecophysiological studies of the invasive weed Chromolaena odorata (L.) King and Robinson and its control in KwaZulu-Natal by Kubendran Kista Naidoo Submitted in fulfillment of the academic requirements for the degree of Doctor of Philosophy in the School of Life Sciences University of KwaZulu-Natal, Westville campus, Durban December 2013 Ecophysiological studies of the invasive weed Chromolaena odorata (L.) King and Robinson and its control in KwaZulu-Natal by Kubendran Kista Naidoo As the candidate’s supervisor I have/have not approved this thesis for submission ___________________ ________________ Professor G. Naidoo Date (Supervisor) ___________________ ________________ Dr. Y. Naidoo Date (Co-supervisor) PREFACE The experimental work described in this thesis was carried out in the School of Life Sciences, University of KwaZulu-Natal from January 2002 to December 2007 under the supervision of Professor G. Naidoo and Dr. Y. Naidoo. These studies represent original work by the author and have not otherwise been submitted in any form for any degree or diploma to any tertiary institution. Where use has been made of the work of others, it is duly acknowledged in the text. _____________________ Kubendran Kista Naidoo i DECLARATION 1: PLAGIARISM I, _________________________________________________________________ declare that 1. The research reported in this thesis, except where otherwise indicated, is my original research. 2. This thesis has not been submitted for any degree or examination at any other university. 3. This thesis does not contain other person’s data, pictures, graphs or other information, unless specifically acknowledged as been sourced from other persons. 4. This thesis does not contain other person’s writing, unless specifically acknowledged as been sourced from other researchers. Where other written sources have been quoted, then: a) Their words have been re-written but the general information attributed to them has been referenced. b) Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced. 5. This thesis does not contain text, graphics or tables copied and pasted from the internet, unless specifically acknowledged, and the source being detailed in the thesis and in the Reference sections. _______________________ Kubendran Kista Naidoo ii DECLARATION 2: PUBLICATIONS Details of contributions to publications that form part and /or include research presented in this thesis: Publication 1 Naidoo, K. K., Coopoosamy, R. M. & Naidoo, G. 2011. Screening of Chromolaena odorata (L.) King and Robinson for antibacterial and antifungal properties. J. Med. Plants Res. 5, 4859-4862. ______________________ Kubendran Kista Naidoo iii DEDICATION To my darling wife, Mayendri Moodley and beloved children, Prishari and Shreyaal. iv ACKNOWLEDGEMENTS I thank Professor G. Naidoo and Dr. Y. Naidoo for supervising this thesis. Thanks also to Nigel Bragg for help with statistics, Dr. Anette Mienie (Director: Research, Mangosuthu University of Technology) for funding and support, National Research Foundation for funding and lastly to my wife, Mayendri Moodley for proofreading this dissertation. v General abstract Despite increased interest in the control and spread of the alien weed, Chromolaena odorata, little is known of its photosynthetic characteristics under field conditions. The aim of the study was to obtain a better understanding of the ecophysiological attributes of C. odorata that contribute to its invasive success. Photosynthetic performance of C. odorata was evaluated by monitoring diurnal changes in gas exchange, chlorophyll a fluorescence and plant water relations. Gas exchange characteristics of plants growing in exposed and shaded environments, as well as seasonal patterns, were evaluated. The response of C. odorata to water stress was also determined. Chromolaena odorata exhibited high CO2 uptake rates with no light saturation. Shade plants had significantly larger leaf surface areas and greater concentrations of total chlorophyll, total carotenoids and chlorophylls a and b than sun plants. Relatively high photosynthetic uptake rates in C. odorata may allow for greater carbon gain in high light environments thus contributing to increased growth and spread of the species. Chromolaena odorata can successfully acclimatise to low photosynthetic photon flux density (PPFD), thus, outcompeting less tolerant species under low light conditions. Leaf conductance, CO2 uptake, transpiration and chlorophyll fluorescence parameters in winter were tightly coupled to summer. Plants had higher water use efficiency (WUE) in summer compared to winter, probably to maximise CO2 uptake and minimise water loss. There was a progressive decrease in leaf water potential with increase in water stress in water stressed (WS) plants. The leaves of WS plants showed signs of severe wilting 10 days after the onset of stress compared to well watered (WW) plants. Increased proline concentration and leaf wilting probably increase (WUE) and may be an adaptive strategy to protect against dehydration injury. vi The effects of the herbicide, glyphosate, on gas exchange and translocation were studied. Glyphosate treatment decreased leaf conductance leading to a reduction in CO2 uptake and transpiration. Glyphosate is a mobile herbicide that is transported from leaves to roots and caused death of plants within a week of treatment. The potential antimicrobial properties of the weed were evaluated using selected bacteria and fungi. Crude leaf extracts exhibited some antibacterial and antifungal activity. Extracts from the weed are unlikely to be useful antimicrobial sources due to low concentrations of active compounds. A co-ordinated strategy, taking into account the high plasticity of the weed, is needed to curtail the spread of C. odorata. The ecophysiological responses to environmental conditions should be considered when planning management and control strategies for C. odorata. vii List of contents 1. Literature review 1.1. Plant description........................................................................... 1 1.2. Common names........................................................................... 2 1.3. Taxonomy.................................................................................... 3 1.4. Classification and nomenclature.................................................. 4 1.4.1. Classification........................................................................ 4 1.4.2. Nomenclature....................................................................... 4 1.5. Origin of C. odorata.................................................................... 5 1.6. Habitat and distribution................................................................ 5 1.6.1. World.................................................................................... 5 1.6.2. South Africa.......................................................................... 7 1.6.3. Potential to spread................................................................. 9 1.7. Weediness in South Africa........................................................... 9 1.7.1. History of invasion............................................................... 9 1.7.2. Current status and legislation................................................ 10 1.7.3. Habitat destruction............................................................... 10 1.8. Methods of control....................................................................... 12 1.8.1. Mechanical............................................................................ 12 1.8.2. Chemical............................................................................... 12 1.8.3. Biocontrol............................................................................ 16 1.8.4. Cultural................................................................................ 19 1.8.5. Integrated ............................................................................ 20 1.9. Economic importance.................................................................. 21 1.9.1. Effects on flora..................................................................... 21 1.9.2. Effects on fauna.................................................................... 23 1.9.3. Medicinal properties............................................................. 24 1.10. Physiological studies.............................................................. 24 1.11. References............................................................................... 25 viii 2. Gas exchange characteristics 2.1. Abstract........................................................................................ 39 2.2. Introduction.................................................................................. 39 2.3. Materials and methods................................................................. 41 2.3.1. Study area............................................................................. 41 2.3.2. Gas exchange........................................................................ 41 2.3.3. Chlorophyll fluorescence...................................................... 41 2.3.4. Water use efficiency............................................................. 42 2.3.5. Leaf water potential.............................................................. 42 2.3.6. Statistics................................................................................ 43 2.4. Results.........................................................................................