The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Usage and Control of Solid-State Lighting for Plant Growth

Paulo Pinho

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 19th of September, 2008, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9502-9)   [2515 KB]
Dissertation is also available in print (ISBN 978-951-22-9501-2)


The work begins with an introductory part in which the basic aspects related to the photosynthetic radiation, the photobiology of plants and the technology of light-emitting diodes (LEDs) are overviewed. It is followed by a review of related research works that have been conducted during the last two decades, and by the main design issues of LED luminaires for plant growth. The following part of the work reports the experimental growth tests performed. The effects of the radiation emitted by spectrally tailored LED luminaires on plant growth have been investigated. A total of four growth tests using lettuce and radish cultivars were performed. Two basic approaches were used to investigate the effects and the future possibilities of the usage of solid-state lighting (SSL) in plant growth. The first approach evaluates the growth development of lettuce plants in real greenhouse conditions using LEDs as supplementary light sources to natural daylight. In the second approach the evaluation was carried out with a total absence of natural daylight by growing lettuce and radish plants in phytotron-chamber conditions. The effects of SSL treatments on the growth development and quality of crops were compared with reference lighting systems composed of conventional and well-established light-source technologies, such as fluorescent and high-pressure sodium lamps. During the process of the investigation, the need to coherently quantify and evaluate the spectral quality of the radiation in terms of its photosynthetic appetence arose. Different metrics are still been used indiscriminately to quantify radiation used by plants to perform photosynthesis. Therefore, the existing metrics are discussed and a new proposal for coherent systematization is presented. The proposed system is referred to phyllophotometric and it is developed using the average photosynthetic spectral quantum yield response curve of plants. The results of the growth tests showed that the usage of SSL in plant growth offers an unprecedented possibility to optimise the morphogenesis, the photosynthesis and the nutritional quality of crops. This can be done by controlling the quantity and the spectral composition of the radiation provided, areas where LED-based luminaires excel. These possibilities can contribute to respond to the increasing demand for high-quality horticultural products by the consumers and to the conservation of global natural environment and resources.

This thesis consists of an overview and of the following 9 publications:

  1. Paulo Pinho, Oskari Moisio, Eino Tetri, and Liisa Halonen. 2004. Photobiological aspects of crop plants grown under light emitting diodes. In: Proceedings of the CIE Expert Symposium '04 on LED Light Sources: Physical Measurement and Visual and Photobiological Assessment. Tokyo, Japan. 7-8 June 2004. CIE x026:2004, pages 71-74. © 2004 International Commission on Illumination (CIE). By permission.
  2. O. Moisio, P. Pinho, E. Tetri, and L. Halonen. 2004. Controlling colour temperature of LED-luminaire. In: Proceedings of the 10th International Symposium on the Science and Technology of Light Sources. Toulouse, France. 18-22 July 2004, pages 375-376. © 2004 Institute of Physics Publishing. By permission.
  3. Paulo Pinho, Eino Tetri, and Liisa Halonen. 2005. Design and performance assessments of solid state light sources for plant growth. In: Proceedings of the 10th European Lighting Conference Lux Europa 2005: Lighting for Humans. Berlin, Germany. 19-21 September 2005, pages 297-301. © 2005 Deutsche Lichttechnische Gesellschaft (LiTG). By permission.
  4. Oskari Moisio, Mika Pajula, Paulo Pinho, Eino Tetri, Liisa Halonen, and Raimo Sepponen. 2005. Use of junction temperature in control of CCT in LED luminaire. In: Proceedings of the CIE Midterm Meeting and International Lighting Congress - Congreso Internacional de Iluminación. León, Spain. 12-21 May 2005, pages 328-334. © 2005 International Commission on Illumination (CIE). By permission.
  5. Paulo Pinho, Eino Tetri, and Liisa Halonen. 2006. Synergies of controller-based LED drivers and quality solid-state lighting. In: Proceedings of the 2nd Conference on Ph.D. Research in Microelectronics and Electronics (PRIME 2006). Otranto (Lecce), Italy. 12-15 June 2006, pages 405-408. © 2006 IEEE. By permission.
  6. A. Urbonavičiūtė, P. Pinho, G. Samuolienė, P. Duchovskis, P. Vitta, A. Stonkus, G. Tamulaitis, A. Žukauskas, and L. Halonen. 2007. Effect of short-wavelength light on lettuce growth and nutritional quality. Scientific Works of the Lithuanian Institute of Horticulture and Lithuanian University of Agriculture. Sodininkystė ir Daržininkystė, volume 26, number 1, pages 157-165. © 2007 Lithuanian Institute of Horticulture (LIH). By permission.
  7. A. Urbonavičiūtė, P. Pinho, G. Samuolienė, P. Duchovskis, P. Vitta, A. Stonkus, G. Tamulaitis, A. Žukauskas, and L. Halonen. 2007. Influence of bicomponent complementary illumination on development of radish. Scientific Works of the Lithuanian Institute of Horticulture and Lithuanian University of Agriculture. Sodininkystė ir Daržininkystė, volume 26, number 4, pages 309-316. © 2007 Lithuanian Institute of Horticulture (LIH). By permission.
  8. P. Pinho, R. Lukkala, L. Särkkä, E. Tetri, R. Tahvonen, and L. Halonen. 2007. Evaluation of lettuce growth under multi-spectral-component supplemental solid state lighting in greenhouse environment. International Review of Electrical Engineering (I.R.E.E.), volume 2, number 6, pages 854-860. © 2007 Praise Worthy Prize. By permission.
  9. Paulo Pinho, Tuija Rosvall, Eino Tetri, Marjukka Eloholma, and Liisa Halonen. 2008. Light emitting diodes in plant growth: Comparative growth test in greenhouse and evaluation of photosynthetic radiation. Helsinki University of Technology, Department of Electronics, Lighting Unit, Report 48. © 2008 by authors.

Errata of publications 3, 6, 7 and 8

Keywords: light emitting diode, plant growth, control of light spectrum, solid-state lighting, phyllophotometry

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© 2008 Helsinki University of Technology

Last update 2011-05-26