In northern latitudes, solar light levels during the winter can be insufficient to maintain production levels and product quality, due to the low light intensities and short photoperiods ( Davis and Burns, 2016). Light is considered to be the most important environmental factor affecting plant development, growth, and production in greenhouse horticulture. These results show that positive effects of altered spectral compositions on physiological responses were only moderately compensated by increased susceptibility to fungal pathogens, which offers perspective for a sustainable greenhouse horticulture. These differences might be due to the plant defenses acting against these pathogens evolving from two different regulatory pathways. The treatments with additional far-red light reduced the infection rate of powdery mildew, but increased botrytis infection. swirskii mites between light treatments, nor did light treatment have an effect on the vertical distribution of these predatory mites in the plants. There were no differences in population growth of A. Far-red light increased biomass partitioning into the fruits, at the expense of the leaves. In the generative phase, total shoot biomass and fruit fresh weights were higher under additional far-red light, followed by the treatments where far-red partly replaced PPFD. Stem length increased with far-red, irrespective of PPFD and the percentage of blue light. Plant biomass in the vegetative phase increased when additional far-red light was supplied. Effects of white light or additional UV-B light on plant resilience was tested, compared to the reference (5% blue, 5% green, and 90% red light). Far-red light either was supplied additionally to the photosynthetic photon flux density (PPFD) or partially replaced PPFD, while maintaining total photon flux density (PFD). The effects of a reduced red/far-red (R:FR) ratio were studied under two ratios of red to blue light. These effects were related to the spectral effects on the establishment of populations of the predatory mite Amblyseius swirskii and plant resilience against the biotrophic fungus powdery mildew, the necrotrophic fungus botrytis, and the herbivorous arthropod Western flower thrips. In this study, we investigated the effects of light spectrum against a background of sunlight on growth and development of Solanum melongena. Spectral composition not only affects crop physiology but may also affect the biology of pathogens, pests, and their natural enemies, both directly and indirectly through an impact on induced plant resistance. Over the last decade, LED lighting has gained considerable interest as an energy-efficient supplemental light source in greenhouse horticulture that can change rapidly in intensity and spectral composition.
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