DEPARTMENT OF AGRICULTURAL SCIENCES UNIVERSITY OF NAPLES FEDERICO II Ph.D. Thesis in Agricultural and Food Sciences LUIGI GENNARO IZZO Improving plant physiological performance and growth by increasing the efficiency of lighting systems Ph.D. Coordinator: Prof. Guido D’Urso Principal Supervisor: Prof. Giovanna Aronne Co-supervisor: Dr. Carmen Arena XXXI Cycle Academic year 2018/2019 “…whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.” Charles R. Darwin, The origin of species Preface The work presented in this thesis was carried out in the period from December 2015 to November 2018 at the Department of Agricultural Sciences and at the Department of Biology of the University of Naples Federico II. Principle supervisor was Prof. Giovanna Aronne and Co-supervisor was Dr. Carmen Arena. A period of six months was spent working with Dr. Celina Gómez in the Environmental Horticulture Department at the University of Florida. The project was funded by the Italian Space Agency (ASI) and the European Space Agency (ESA) within the framework of MELiSSA (Micro-Ecological Life Support System Alternative). Index Introduction ................................................................................................. 5 Chapter 1 ................................................................................................... 10 Increasing efficiency of crop production with LEDs ................................... 11 1.1. Abstract ..................................................................................................... 11 1.2. Introduction ............................................................................................... 12 1.3. Monochromatic LEDs for plant production ................................................. 12 1.3.1. Light-quality control of plant growth and development ........................ 12 1.3.2. Controlling seasonality of flowering plants .......................................... 16 1.3.3. Controlling physiological disorders...................................................... 18 1.3.4. Reducing incidence of pest and disease pressure .............................. 19 1.4. Reductions in energy consumption ........................................................... 21 1.4.1. Intracanopy lighting (ICL) .................................................................... 21 1.4.2. Targeted lighting ................................................................................. 22 1.4.3. Dynamic control of LEDs .................................................................... 22 1.5. Future of LEDs .......................................................................................... 24 1.5.1. Vertical farms (VFs) ............................................................................ 24 1.5.2. Space farming .................................................................................... 25 1.5.3. Off-grid plant production ..................................................................... 26 1.6. References ............................................................................................... 26 Chapter 2 ................................................................................................... 36 Index 1 Light quality shapes morpho-functional traits and pigment content of green and red leaf cultivars of Atriplex hortensis................................................. 37 2.1. Abstract ..................................................................................................... 37 2.2. Introduction ............................................................................................... 38 2.3. Materials and Methods .............................................................................. 41 2.3.1. Plant material and growing conditions ................................................ 41 2.3.2. Lighting treatments ............................................................................. 42 2.3.3. Quantification of morphological traits .................................................. 42 2.3.4. Microscopy and digital image analysis ................................................ 43 2.3.5. Chlorophyll a fluorescence measurements ......................................... 43 2.3.6. Determination of pigment content ....................................................... 44 2.3.7. Statistical analysis .............................................................................. 44 2.4. Results ...................................................................................................... 45 2.5. Discussion ................................................................................................ 49 2.6. Conclusions .............................................................................................. 54 2.6. Conclusions .............................................................................................. 54 2.7. References ............................................................................................... 55 Chapter 3 ................................................................................................... 62 Growth and physiological responses of lettuce grown under pre-dawn or end- of-day sole-source light-quality treatments ................................................ 63 3.1. Abstract ..................................................................................................... 63 3.2. Introduction ............................................................................................... 63 3.3. Materials and methods .............................................................................. 66 3.3.1. Plant material and growing conditions .................................................... 66 3.3.2. Lighting treatments ............................................................................. 66 Index 2 3.3.3. Data collection and plant measurements ............................................ 68 3.3.4. Data analysis ...................................................................................... 70 3.4. Results ...................................................................................................... 70 3.4.1. Growth responses .............................................................................. 70 3.4.2. Physiological responses ..................................................................... 71 3.5. Discussion ................................................................................................ 73 3.6. References ............................................................................................... 75 Chapter 4 ................................................................................................... 78 Gas exchange and leaf anatomy of lettuce in response to blue and red LEDs as a sole-source lighting ............................................................................ 79 4.1. Abstract ..................................................................................................... 79 4.2. Introduction ............................................................................................... 79 4.3. Materials and methods .............................................................................. 81 4.3.1. Plant material and growing conditions ................................................ 81 4.3.2. Lighting treatments ............................................................................. 81 4.3.3. Growth and morphological measurements .......................................... 82 4.3.4. Physiological measurements .............................................................. 83 4.3.5. Anatomical leaf traits measurement .................................................... 83 4.3.6. Data analysis ...................................................................................... 83 4.4. Results ...................................................................................................... 83 4.4.1. Growth and morphology ..................................................................... 83 4.4.1. Physiology .......................................................................................... 84 4.4.1. Anatomy ............................................................................................. 85 4.5. Discussion ................................................................................................ 85 4.6. Conclusions .............................................................................................. 87 Index 3 4.7. References ............................................................................................... 88 Chapter 5 ................................................................................................... 91 MULTITROP: an educational and scientific project on root tropism interactions in microgravity ....................................................................... 92 5.1. Abstract ..................................................................................................... 92 5.2. Introduction ............................................................................................... 93 5.2.1. Educational aims and activities ........................................................... 93 5.2.2. Theory ................................................................................................ 95 5.2.3. Scientific aims....................................................................................