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ISHS Acta Horticulturae 1134: VIII International Symposium on Light in Horticulture

The effect of diurnal light intensity distribution on plant productivity in a controlled environment

Authors:   G.M. Bochenek, I. Fällström
Keywords:   DLI, Lactuca sativa, LED luminaries, light fluctuations, Ocimum basilicum
DOI:   10.17660/ActaHortic.2016.1134.21
Abstract:
Leafy crops, basil 'Aroma 2' and lettuce 'Galiano', were grown under six LED light regimes of the same spectral composition, photoperiod, and daily light integral (DLI), but different distribution of light intensities during the day. In natural environments, plants experience rapid changes of light conditions. Variation in light intensity influences vital plant functions, such as photosynthetic activity, carbohydrate metabolism, leaf expansion, etc., and has an effect on productivity. Intelligent LED technology enables a high level of control over the amount of light provided to plants as supplemental or sole source lighting. Diurnal variation of light intensities can be based on plant responses and/or economic factors such as energy price. It is well known that plant biomass depends on the total amount of light provided to plants, but the effects of different strategies of providing light remains speculative. Here we present a comparison of biomass accumulation and growth performance of plants cultivated under constant, fluctuating (changing within minutes), sinusoid, and increasing at the beginning or the end of photoperiod light regimes. Results show that plant growth is best when light intensity is constant or imitates the natural distribution. Fluctuations or large changes in light intensity may decrease plant productivity. However, the differences were not large enough to compromise the visual quality of the crops.

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