PHYSIOLOGICAL AND BIOCHEMICAL EFFECT OF BIOSTIMULANTS ON ABELMOSCHUS ESCULENTUS (L.) AND CLEOME GYNANDRA (L.) By Gugulethu Makhaye Submitted in fulfilment of the requirement for the degree of Master of Science (Agriculture), Horticultural Science School of Agricultural, Earth and Environmental Sciences College of Agriculture, Engineering and Science University of KwaZulu-Natal Pietermaritzburg Republic of South Africa Supervisor: Prof S. Tesfay (UKZN) Co-Supervisor: Prof S.O. Amoo (ARC) Co-Supervisor: Prof O.A. Aremu (UKZN & NWU) i Table of Contents College of Agriculture, Engineering and Science; Declaration 1 – Plagiarism ........................ vi Student Declaration ..................................................................................................................... vii Declaration by Supervisors ........................................................................................................ viii Conference Contributions from this Thesis ................................................................................ ix Publications from this Thesis ......................................................................................................... x Potential Publications from this Thesis ....................................................................................... xi Acknowledgements ...................................................................................................................... xii List of Figures ............................................................................................................................. xiii List of Tables ................................................................................................................................. xv List of Abbreviations ................................................................................................................. xvii Abstract ........................................................................................................................................ xix Chapter 1: Introduction ..................................................................................................................... 1 1.1. Background ................................................................................................................. 1 1.2. Potential of biostimulants on plant growth .............................................................. 1 1.3. Underutilized multipurpose plants............................................................................ 2 1.3.1. Cleome gynandra L. ................................................................................................. 2 1.3.2. Abelmoschus esculentus (L.) Moench ...................................................................... 2 1.4. Problem statement ...................................................................................................... 3 1.5. Aim and objectives ...................................................................................................... 3 1.6. Research questions ...................................................................................................... 4 1.7. Hypothesis ................................................................................................................... 4 1.8. Overview of chapters in this thesis ........................................................................... 4 Chapter 2: Literature review ............................................................................................................. 5 2.1. Introduction ......................................................................................................................... 5 2.2. Approaches to improve soil fertility ................................................................................... 5 2.1.1. Plant biostimulants and agricultural production ....................................................... 7 2.3. Multipurpose plants .......................................................................................................... 22 2.3.1. Distribution and general morphology of Abelmoschus and Cleome species ................ 22 2.4. Nutritional value of Abelmoschus and Cleome species .......................................... 24 ii 2.4.1. Abelmoschus esculentus ................................................................................................ 24 2.4.2. Cleome gynandra .......................................................................................................... 25 2.5. Medicinal properties of Abelmoschus and Cleome species ............................................. 25 2.5.1. Abelmoschus esculentus ................................................................................................ 26 2.5.2. Cleome gynandra .......................................................................................................... 26 2.6. Phytochemistry of Abelmoschus esculentus and Cleome gynandra ...................... 26 2.7. Conclusion .......................................................................................................................... 28 Chapter 3: Effects of biostimulants on the germination of Abelmoschus esculentus and Cleome gynandra genotypes ........................................................................................................................ 29 3.1. Introduction ........................................................................................................................... 29 3.2. Materials and methods .......................................................................................................... 29 3.2.1. Source of biostimulants and seeds .................................................................................... 29 3.2.2. Soaking duration ............................................................................................................... 30 3.2.3. Seed germination using biostimulants .............................................................................. 30 3.2.4. Data analysis ..................................................................................................................... 31 3.3. Results ..................................................................................................................................... 31 3.3.1. Effect of soaking period on Abelmoschus esculentus and Cleome gynandra seeds germination parameters. ............................................................................................................. 31 3.3.2. Effect of genotype on Abelmoschus esculentus and Cleome gynandra germination parameters. .................................................................................. Error! Bookmark not defined. 3.3.3. Effect of biostimulant treatments on Abelmoschus esculentus and Cleome gynandra genotypes germination parameters. ............................................................................................ 33 3.3.4. Interaction effect of genotype and treatment of Abelmoschus esculentus and Cleome gynandra germination parameters. ............................................................................................. 36 3.4. Discussion ............................................................................................................................... 41 3.4.1. Effect of genotype on germination parameters of Abelmoschus esculentus and Cleome gynandra ..................................................................................................................................... 41 3.4.2. Effect of biostimulant application and their interaction effect with Abelmoschus esculentus and Cleome gynandra genotypes on germination parameters. ................................................... 41 3.5. Conclusion .............................................................................................................................. 43 Chapter 4: Effects of biostimulants on the growth and yield responses of Abelmoschus esculentus and Cleome gynandra genotypes. ................................................................................................... 44 iii 4.1. Introduction ........................................................................................................................... 44 4.2. Materials and methods .......................................................................................................... 44 4.2.1. Source of biostimulants and seeds .................................................................................... 44 4.2.2. Planting, seedling growth and yield .................................................................................. 45 4.2.3. Data analysis ..................................................................................................................... 46 4.3. Results ..................................................................................................................................... 46 4.3.1. Effect of genotype on growth and yield of Abelmoschus esculentus and Cleome gynandra .................................................................................................... Error! Bookmark not defined. 4.3.2. Effect of biostimulant treatments on growth and yield of Abelmoschus esculentus and Cleome gynandra. ....................................................................................................................... 46 4.4. Discussion ..............................................................................................................................