FLOWERING IN HELICONIA ROSTRATA RUIZ & PA VON 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 DECEMBER 2000 BY Norberto Maciel Dissertation Committee: Richard A. Criley, Chairperson Kent D. Kobayashi Robert Pauli Willian S. Sakai David Webb IN MEMORIAM Antonio Oliveira De Sousa (My Father) Because pursuing this goal I did not share his last moments 111 ACKNOWLEDGMENTS I would like to express my sincere gratitude to my chairperson. Dr. Richard A. Criley for inviting me come to the University of Hawaii, his guidance, and understanding. I very much appreciate my other committee members Dr. Kent D. Kobayashi, Dr. Robert Pauli, Dr. William S. Sakai, and Dr. David D. Webb for their assistance and suggestions. Thanks to: Dr. Osamu Kawabata for the suggestions in the statistical analysis; Dr. David D. Webb and Dr. Adelheid Kuehnle for the help with equipment and chemicals; and Mr Bob Hirano and the Lyon Arboretum for providing material of Heliconia rostrata used in one of the experiments. My special thanks to Mr Ronald Matsuda and Craig Okasaki of the Magoon facility for the great help. I want to express my gratitude to faculty, staff and colleagues in the Department of Horticulture for sharing with me their skills, help, and friendship. I will never forget the help and kindness of the friends that I meet in Hawaii, especially for the scholarly help from Derrick Agboka, Renee and Adrian Ares, Douglas Gaskill, Michael Melzer, Javier Mendez, Monica Mejia, Teresa Restom and Mario Serracin. 1 also would like to acknowledge "Universidad Centroccidental Lisandro Alvarado" and Conicit, in Venezuela, for the economic support. Finally to my family, colleagues (in especially Norca Mogollon) and friends in Venezuela for their help, encouragement and moral support. IV ABSTRACT The factors that affect the seasonal blooming of Heliconia rostrata in Hawaii and how to use them to obtain off season flowering were studied. These studies show that this pattern of blooming is due to photoperiod. Competent shoots (3 or more unfurled leaves) from different experiments subjected to short days (SD) less than 11.5 hours for periods of 4 to 8 weeks did flower. Plants growing under daylength >13 hours or <12 hours but with supplemental light or night break did not flower. The critical daylength was between 1 Ih 45m and 12h. On the other hand, night temperature did not induce flower initiation. Therefore, H. rostrata is a typical obligate or qualitative short day plant. The imposition of SD allows an earlier blooming season by inducing flowering, whereas the extension of daylength delays blooming by inhibiting the induction. The emergence of the inflorescence from the shoots occurred 21 to 29 weeks after the onset of SD. Under Hawaii's natural daylength, the floral apex was observed microscopically 2 months prior to blooming. Floral shoots had from 6 to 12 leaves, depending on the number present at induction, while in non-induced shoots, the number of leaves can reach up to 15 since the apex would still produce leaves even if it had reached the competent stage to be induced. Shoot density, daylength, and shoot generation were related with floral shoots and apex death. More inflorescences were developed in pots with one shoot per generation than in pots with all shoots per generation. At higher shoot density there were more dead shoots. The highest percentage of flowering shoots was also observed under continuous SD from all generations of shoots than in plants under 8 weeks of SD followed by long days. The results also showed a differential response between floral and dead shoots with the generations. The second generation of shoots showed the highest flowering. The highest shoot death occurred at the first generation. Stage of development of shoots at the moment of induction and competition among shoots for assimilates were suggested as possible causes of apex shoot death. VI TABLE OF CONTENTS Dedication................................................................................................................................. iii Acknowledgments....................................................................................................................iv Abstract...................................................................................................................................... v List of Tables............................................................................................................................ xi List of Figures..........................................................................................................................xii Chapter 1: Introduction.............................................................................................................1 Chapter 2: Literature Review....................................................................................................4 2.1 Botany in Heliconia............................................................................................4 2.1.1. Taxonomy.............................................................................................. 4 2.1.2. Plant Characteristics...............................................................................4 2.1.3. Ecophysiology........................................................................................6 2.2. Horticulture........................................................................................................8 2.2.1. Status in the Ornamental Industry.........................................................8 2.2.2. Research..................................................................................................9 2.3. Flowering............................................................................................................11 2.4. Factors Affecting Flowering.............................................................................13 2.4.1. Environmental Factors......................................................................14 Light Intensity..................................................................................... 14 Daylength.............................................................................................15 Temperature........................................................................................ 19 VU 2.4.2. Endogenous Factors........................................................................... 20 2.4.3. Factors Promoting Abortion...............................................................24 Assimilates Allocation........................................................................ 24 Plant Density and Competition..................................................... ,...26 Environmental Factors........................................................................ 28 Plant Growth Regulators.....................................................................29 Chapter 3: The Transition to Flowering in H. rostrata Ruiz & Pav6n. Macromorphological and Anatomical Changes at the Shoot Apex................. 33 3.1. Abstract................................................................................................................ 33 3.2. Introduction..........................................................................................................34 3.3. Materials and Methods........................................................................................36 3.4. Results and Discussion....................................................................................... 37 3.4.1. Blooming Season.................................................................................37 3.4.2. Shoot Characteristics.......................................................................... 38 3.4.3. Apices Status........................................................................................42 3.4.4. Anatomy............................................................................................... 47 3.5. Conclusions.......................................................................................................... 54 Chapter 4: Daylength and Night Temperature on the Induction of Flowering and Growth of H. rostrata Ruiz & Pavon................................................................................56 4.1. Abstract................................................................................................................ 56 4.2. Introduction..........................................................................................................57 vni 4.3. Materials and Methods........................................................................................60 4.3.1. Effect of Day length (Exp. 1)...............................................................60 4.3.2. Effect of Daylength and Number of Weeks (Exp. 2)........................ 61 4.3.3. Effect of Temperature and Daylength (Exp. 3)................................. 63 4.3.4. Data Analysis.......................................................................................64 4.4. Results and Discussion.......................................................................................65 4.4.1. Effect of daylength (Exp. 1)...............................................................65 4.4.2. Effect of daylength and number of weeks (Exp. 2)...........................72 4.4.3. Effect of temperature and daylength (Exp. 3).....................................83 4.5.