Horticultural Reviews, Volume 43

Jules Janick, Jules Janick

• Publisher: Wiley-Blackwell
• Year: 2015
• ISBN:
  9781119107767
• Edition: 1
• Topic: Biowissenschaften
• Subtopic: Botanik

Horticultural Reviews presents state-of-the-art reviews on topics in horticultural science and technology covering both basic and applied research. Topics covered include the horticulture of fruits, vegetables, nut crops, and ornamentals. These review articles, written by world authorities, bridge the gap between the specialized researcher and the broader community of horticultural scientists and teachers.

1
Light-Emitting Diodes in Horticulture

Cary A. Mitchell, Michael P. Dzakovich, Celina Gomez, and Roberto Lopez

Department of Horticulture & Landscape Architecture Purdue University West Lafayette, IN USA

John F. Burr

Krannert School of Business Management Purdue University West Lafayette, IN USA

Richardo Hernández and Chieri Kubota

School of Plant Sciences The University of Arizona Tucson, AZ USA

Christopher J. Currey

Department of Horticulture Iowa State University Ames, IA USA

Qingwu Meng and Erik S. Runkle

Department of Horticulture Michigan State University East Lansing, MI USA

Christopher M. Bourget and Robert C. Morrow

Orbital Technologies Corporation Madison, WI USA

Arend J. Both

Department of Environmental Sciences Rutgers University New Brunswick, NJ USA

Abstract

Light-emitting diodes (LEDs) have great potential to revolutionize lighting technology for the commercial horticulture industry. Unique LED properties of selectable, narrow-spectrum emissions, long life spans, cool photon-emitting surfaces, and rapidly improving energy use efficiency encourage novel lighting architectures and applications with promising profitability potential. In greenhouses, such unique properties can be leveraged for precise control of flowering and product quality for the floriculture industry, for energy-efficient propagation of ornamental and vegetable transplants, and for supplemental lighting of high-wire greenhouse vegetable crops for all-year production. In a sole-source lighting mode, LEDs can also be used for transplant production, as well as for production of rapid-turning vegetable and small fruit crops. Evidence is accumulating that nutritional and health attributes of horticultural products may be enhanced by specific wavelength combinations of narrow-spectrum light from LEDs. During periods of seasonally limited solar light, LEDs have potential to enhance daily light integral in greenhouses by providing supplemental photosynthetic radiation, particularly of red and blue light. The cool photon-emitting surfaces of LEDs permit their novel placement relative to crop foliar canopies, including close-canopy overhead lighting as well as within-canopy lighting, which greatly reduces electrical energy requirements while maintaining adequate incident photon fluxes. Because of the small size of individual LEDs and narrow beam angles from LED arrays, light distribution can be highly targeted and waste of light from LEDs minimized compared with other light sources traditionally used for horticulture. Prescriptions of spectral blends (e.g., red:far-red and red:blue ratios) can be developed for LEDs to accomplish specific photomorphogenic goals for seedling development, flowering, and possibly yield and produce quality. LED light quality may also be useful to control pest insects and to avoid physiological disorders otherwise caused by low-intensity or narrow-spectrum lighting. Complex factors such as rapidly improving LED luminous efficacy, favorable mass-manufacturing costs, local costs of electrical energy, and capital investment will interact to determine for which applications and when LEDs become the dominant lighting technology in horticulture.

KEYWORDS: energy savings; greenhouse; intracanopy; light quality; night interruption; photomorphogenesis; photoperiod; propagation; sole-source lighting; solid-state lighting; supplemental lighting

1. Abbreviations
2. I. Introduction
3. II. Properties of LEDs
   1. A. What Are LEDs?
   2. B. LEDs as a Horticultural Lighting System
   3. C. LED Packaging
   4. D. Wavebands of Interest
   5. E. Performance Trends and Outlook
   6. F. Misconceptions About LED Lighting
4. III. Design Considerations
   1. A. General Design Requirements
   2. B. Thermal Management
   3. C. Control
      1. 1. Warm-Up and Restrike Times
      2. 2. “Smart” Control Systems
   4. D. LED Lighting Systems
      1. 1. Intracanopy Lighting
      2. 2. Overhead Point Source
      3. 3. Overhead Distributed Source
   5. E. Strategies for Maximizing Life and Maintaining Output
5. IV. Historical Overview of LED Use in Horticulture
6. V. Summary of Plant Experiments in Space with LEDs
7. VI. Horticultural Applications of LEDs
   1. A. Providing Photosynthetic Light for Young Ornamental Plants
      1. 1. Introduction
      2. 2. Supplemental Lighting
      3. 3. Sole-Source Lighting
   2. B. Photoperiodic Lighting with LEDs
      1. 1. Historical Background
      2. 2. Red and Far-Red Light
      3. 3. Blue Light
      4. 4. Green Light
      5. 5. Growth Response Parameters
      6. 6. Comparison of LEDs with Traditional Light Sources
   3. C. Propagation of Vegetable Transplants Under LED Lighting
      1. 1. Introduction and Brief History
      2. 2. Improving Transplant Morphology with LED Lighting
      3. 3. Improving Transplant Photosynthesis and Growth
      4. 4. Considerations in Evaluating Electric Lighting for Greenhouses
      5. 5. LEDs for Sole-Source Lighting of Vegetable Transplants
   4. D. LED Applications for Indoor Crop Production
      1. 1. Full-Coverage Sole-Source Lighting
      2. 2. Targeted Close-Canopy Lighting
   5. E. LED Applications for Greenhouse Vegetable Crop Production
      1. 1. Current Standard
      2. 2. Sole-Source Lighting Pretreatments
      3. 3. Supplemental Lighting
      4. 4. Current Status and Challenges
   6. F. The Potential of LEDs to Enhance Produce Quality
      1. 1. Strawberry
      2. 2. Salad and Microgreens
      3. 3. Tomato
      4. 4. Postharvest
      5. 5. Summary
8. VII. LED Lighting and Plant Health
   1. A. Physiological Disorders
   2. B. Insect Pests
9. VIII. LEDs and Light Pollution
   1. A. Control of Spectral Output
   2. B. High Light Intensity
   3. C. High-Resolution Control
10. IX. LED Light Distribution Issues
11. X. LED Environmental and Health Issues
    1. A. Disposal
    2. B. Optical Safety for LEDs
12. XI. Adoption of LED Technology by Horticultural Industries
    1. A. Economics
    2. B. Evolution of Design and Industry
13. XII. The Future of Plant Applications for LEDs
    1. A. Improvements in Technology
    2. B. Improved Use of Light to Achieve Specific Horticultural Goals
14. Literature Cited

Abbreviations

ABRS	Advanced Biological Research System
AC	Alternating current
ASHS	American Society for Horticultural Science
B	Blue
BF	Blue fluorescent
CEWG	Controlled Environments Working Group
DC	Direct current
DE	Day extension
DIF	Day temperature − night temperature
DLC	Dynamic lighting control
DLI	Daily light integral
DOE	Department of Energy
DPPH	2,2-Diphenyl-1-picrylhydrazyl
EOD	End of day
ESD	Electrostatic discharge
FL	Fluorescent
FR	Far-red
G	Green
HID	High-intensity discharge
HPS	High-pressure sodium
HR	Hyper-red
IC	Integrated circuit
ICL	Intracanopy lighting
INC	Incandescent
ISS	International Space Station
kWh	Kilowatt hour
LD	Long day
LDP	Long-day plant
LED	Light-emitting diode
lm	Lumen
MH	Metal halide
NASA	National Aeronautics and Space Administration
NBL	Narrowband lighting
NCERA-101	North-Central Extension and Research Activity-101
NI	Night interruption
OH	Overhead
PAR	Photosynthetically active radiation
PBB	Polybrominated biphenyl
PBDE	Polybrominated diphenyl ether
PFR	Far-red-absorbing form of phytochrome
PPF	Photosynthetic photon flux
PR	Red-absorbing form of phytochrome
PS	Photosynthesis
PWM	Pulse-width modulation
QI	Quality index
R	Red
RDM	Root dry mass
RWB	Red + white + blue
SD	Short day
SDP	Short-day plant
SL	Supplemental lighting
SPAD	Relative chlorophyll content
SSBRP	Space Station Biological Research Program
UV	Ultraviolet
VOC	Volatile organic compound
W	Watt
WF	White fluorescent

I. Introduction

Horticultural lighting long has borrowed technology from the lighting industry that was not originally designed or intended for plant growth and development. As a consequence, horticulturists and plant physiologists learned to “make do” with the range of lamps that were available for supplemental or sole-source lighting of horticultural crops. Incandescent lamps became the standard for photoperiod control in greenhouses (Downs et al. 1958). Fluorescent (FL) ± incandescent (INC) lamps were widely used to achieve “normal” plant growth and development in growth chambers (Biran and Kofranek 1976; Bickford 1979), and when high-intensity discharge (HID) lamps came along, they quickly became the standard for supplemental lighting (SL) in greenhouses and for sole-source lighting in phytotrons and some growth chambers (Warrington et al. 1978; Tibbitts et al. 1983). All of these light sources do the job, but also have serious limitations. At the time they were adopted, there were no good alternatives. Incandescent lamps are highly wasteful of energy, are very short-lived (Bickford and Dunn 1972), and are rapidly disappearing from the marketplace. Fluorescent lamps have limited photon output and a short effective life span (Sager and McFarlane 1997). High-intensity discharge lamps require high voltage, emit intense radiant heat (McCree 1984), and require wide spatial separation from plants and/or thermal barriers. Light-emitting diodes (LEDs) were first tested with plants more than 20 years ago (Bula et al....