Finding the Optimal Growth-Light Spectrum for Greenhouse Crops

S.W. Hogewoning, G. Trouwborst, E. Meinen, W. van Ieperen

    Research output: Chapter in Book/Report/Conference proceedingAbstract

    Abstract

    Photosynthesis per unit leaf area is widely used as a measure for crop productivity. However, especially in an open crop (e.g. young plants) morphological responses to light quality that affect light interception are also important. After all, it is the photosynthetic rate per crop area rather than the photosynthetic rate per leaf area that determines productivity. Earlier work showed a substantial biomass increase for young cucumber plants grown under 100% artificial sunlight compared with 100% high pressure sodium light (HPS). Here we show the effect of artificial sunlight as a supplemental light-source by simulating a greenhouse situation in a climate chamber. Tomato plants were grown under 17h artificial sunlight (50% of total PAR) supplemented with 50% HPS, LEDs (red/blue), or artificial sunlight. The 100% artificial sunlight-grown plants produced 32-45% more dry weight, due to morphology allowing a more efficient light interception. Artificial sunlight lamps are important for research, but probably not energy-efficient enough for commercial crop production. Therefore the second aim was to simplify the solar spectrum while retaining enhanced crop productivity. Red/blue/far-red LEDs, at a ratio inducing the same phytochrome photostationary state (PSS) as natural sunlight, and sulfur-plasmalamps, emitting a continuous spectrum in the PAR-region, were tested as supplemental light-sources in a greenhouse experiment. Additionally, red/blue LEDs, HPS (reference) and artificial sunlight lamps (qualitative reference) were tested. Red/blue/far-red resulted in a visual appearance similar to the artificial sunlight-plants, while red/blue LEDs produced the most compact morphology. Red/blue/far-red enhanced dry weight for cucumber (+21%) and tomato (+15%) compared with HPS. Dry weight and compactness were intermediate for sulfur-plasma. The differences were attributable to effects of leaf orientation and positioning on light interception, and not to photosynthesis per unit leaf area. The PSS appears to be a key-factor to control crop morphology, allowing either ‘sunlight’ crop characteristics to enhance productivity, or oppositely to produce more compact plants. Combined utilization of assimilation and signaling properties of light offers novel opportunities for protected crop production.
    Original languageEnglish
    Title of host publicationProceedings of the 7th International Symposium on Light in Horticultural Systems (Book of Abstracts)
    EditorsS. Hemming, E. Heuvelink
    Place of PublicationLeuven
    PublisherISHS
    Pages77
    Publication statusPublished - 2012
    EventVII International Symposium on Light in Horticultural Systems - Wageningen, Netherlands
    Duration: 15 Oct 201218 Oct 2012

    Conference

    ConferenceVII International Symposium on Light in Horticultural Systems
    CountryNetherlands
    CityWageningen
    Period15/10/1218/10/12

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