POSTHARVEST PHYSIOLOGY OF RED GINGER INFLORESCENCE (Alpinia purpurata Vieill K. Schum) A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI’I IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN HORTICULTURE AUGUST 1999 By Theeranuch Chantrachit Dissertation Committee: Robert Pauli, Chairperson Richard Criley Roy Nishimoto Mike Nagao David Webb We certify that we have read this dissertation and that, in our opinion, it is satisfactory in scope and quality as a dissertation for the degree of Doctor of Philosophy in Horticulture. DISSERTATION COMMITTEE ( k ji T .ip ACKNOWLEDGMENTS I would like to express my utmost appreciation to my chairperson, Dr. Robert E. Pauli. I could not have completed my work without his guidance and support. His friendship, understanding, and patience mean more to me than he can possibly know. My deeply thank also go to my other committee members; Dr. Richard A. Criley, Dr. Roy K. Nishimoto, Dr. Mike A. Nagao, and Dr. David D. Webb. Their constructive comments and suggestions have greatly enhanced my education, sharpened my work and made me a better scientist. I will never forget the friendship and support from friends and colleagues in Dr. Pauli’s laboratory; Dr. Nancy J. Chen, Gail Uruu, Theodore Goo, Dr. Ching-Cheng Chen, Dr. Lili Zhou, Dr. Maria Eloisa Q. Reyes (Boots) and her husband, Marcelino U. Reyes (Archie). I sincerely thank them for their helping hands, valuable comments and useful suggestions. The joys that we have shared together will last forever in my memory. I also owe a debt of gratitude to faculty and friends in the Department of Horticulture and Plant Molecular Physiology. Their kindness has helped me get through the difficulty of being away from my family. Finally, from the bottom of my heart, I thank my family and my best friends in Thailand who prove that absence make the heart grow fonder. Because of their encouragement and moral support, I have overcome the most difficult problem in my life. Ill ABSTRACT The postharvest physiology of red ginger inflorescence, including the impact of heat treatment to extend inflorescence vase life, was determined. More than 90% of the inflorescences showed inflorescence wilting or bract browning symptoms or both during senescence. Ethylene and the total count microorganisms in the stem segments and the vase solution had no effect on the development of senescence symptoms. I hypothesized that water balance of the cut stem was associated with inflorescence wilting, whereas sugar content was associated with bract browning symptom. While a relationship between inflorescence wilting and water balance was not confirmed, a positive relationship was established between sugar content and inflorescence vase life as the higher the sugar content in cut stem, the longer the inflorescence vase life. Immersion of the inflorescences in hot water at 40°C for 15 min is recommended as a preconditioning treatment to prevent heat damage to red ginger from the hot water treatment at 50°C for 12 min for insect disinfestation. This combination treatment extends vase life. Extension of inflorescence vase life by the hot water treatment varied with season of harvest and flower variety. Exposure time shorter than 12 min at 50°C was recommended in winter, as the inflorescences had lower thermotolerance than in the summer. Hot water treated inflorescences exhibited a lower rate of respiration than untreated inflorescence, while ethylene production as a result of the treatment was not significantly detected. Inflorescences treated with hot water maintained a higher sugar IV levels for a longer period than untreated inflorescences, and this could explain the vase life extension. Hot water treatment also suppressed negative geotropism in the red ginger inflorescences during horizontal storage. The negative geotropic response was delayed for up to 7 days after the hot water treatment. The sugar content (98%) in the red ginger stem was located in symplast, whereas two percent was attributed to apoplast that is heat resistant as the contents were not affected by the hot water treatment. Sugar metabolism in red ginger inflorescence may be heat sensitive. However, the activity of sugar metabolic enzymes: sucrose phosphate synthase, sucrose synthase and invertase, were not directly related to the changes in sugar content after hot water treatment. It is, therefore, suggested that factors other than the activity of these enzymes affect sugar content of the cut stem. TABLE OF CONTENTS Acknowledgments................................................................................... iii Abstract..................................................................................................... iv List of Tables........................................................................................... ix List of Figures........................................................................................... x Chapter 1. Introduction and Literature Reviews................................... 1 1.1. Introduction........................................................................ 1 1.2. Red ginger (Alpiniapurpurata Vieill K. Schum) 6 1.2.1. Summary of botany and cultivation.................. 6 1.2.2. Vascular system................................................. 7 1.2.3. Postharvest handling.......................................... 8 1.3. Postharvest physiology of cut flower senescence 9 1.3.1. Ethylene production and respiration rate 9 1.3.2. Water balance of the cut stems......................... 11 1.3.3. Vascular blockage of cut flowers..................... 12 1.3.4. Microorganisms in cut flowers......................... 13 1.3.5. Energy sources of cut flowers........................... 14 1.3.6. Plant growth regulators and flower senescence 19 1.4. Sucrose metabolic enzymes.............................................. 2 0 1.4.1. Sucrose phosphate synthase (SPS).................... 22 1.4.2. Sucrose synthase (SS)........................................ 23 1.4.3. Invertase (AI and NI)......................................... 24 1.5. Hot water application......................................................... 25 1.5.1. Hot water and insect disinfestation................... 25 1.5.2. Effect of hot water on living tissues................. 27 1.5.3. Physiological effect of heat treatment.............. 28 Chapter 2. General Materials and Methods.......................................... 31 2.1. Plant materials and general practice.................................. 31 2.2. Evaluation of vase life........................................................ 32 2.3. Determination of postharvest physiological factors 32 2.3.1. Ethylene production and respiration rate 32 2.3.2. Water balance of the cut stem........................... 33 2.3.3. Stem and vase microorganisms........................ 34 2.3.4. Total sugar, sucrose and reducing sugar 35 2.3.5. Starch level......................................................... 37 2.4. Data analysis...................................................................... 38 VI Chapters. Postharvest Physiology of Red Ginger Senescence 42 3.1. Introduction......................................................................... 42 3.2. Materials and methods....................................................... 43 3.2.1. Senescence symptoms......................................... 43 3.2.2. Vase life and inflorescence characteristics 44 3.2.3. Effect of postharvest handling........................... 45 3 .2.4. Postharvest physiology of red ginger senescence........................................................... 46 3.3. Results and discussion........................................................ 47 3.3.1. Senescence symptoms......................................... 47 3.3.2. Vase life and inflorescence characteristics 48 3.3.3. Effect of postharvest handling........................... 50 3.3.4. Postharvest physiology of red ginger senescence........................................................... 54 3.4. Summary.............................................................................. 65 Chapter 4. Hot water and Red Ginger Vase Life.................................. 84 4.1. Introduction......................................................................... 84 4.2. Materials and methods........................................................ 85 4.2.1. Plant material s..................................................... 85 4.2.2. Hot water treatments........................................... 8 6 4.2.3. Preconditioning treatments................................ 87 4.2.4. Preharvest factors on heat sensitivity............... 87 4.3. Results and discussion........................................................ 8 8 4.3.1 . Observation on heat damage symptoms 8 8 4.3.2. Hot water treatments........................................... 8 8 4.3.3. Threshold for hot water treatments.................... 89 4.3 .4. Preconditioning treatment and intervening period.................................................................. 90 4.3.5. Preharvest factors on heat sensitivity................ 92 4.4. Summary.............................................................................. 94 Vll Chapter 5. Effect of Hot water on Postharvest Physiology and geotropic Response.............................................................. 109 5.1. Introduction......................................................................... 109 5.2. Materials and methods......................................................