The Effect of Diffuse Light on Crops
Light is not evenly distributed in Dutch glass greenhouses, but this can be improved with diffuse light. Modern greenhouse coverings are able to transform most of the light entering the greenhouse into diffuse light. Wageningen UR Greenhouse Horticulture has studied the effect of diffuse light on crops for several years. Modelling and experimental studies showed that crops such as fruit vegetables with a high plant canopy as well as ornamentals with a small plant canopy can utilize diffuse light better than direct light. Diffuse light penetrates the middle layers of a high-grown crop and results in a better horizontal light distribution in the greenhouse. Diffuse light is absorbed to a better degree by the middle leaf layers of cucumber, resulting in a higher photosynthesis. The actual photosynthesis of four pot plant species was found to be increased and crop temperatures were lower during high irradiation. The yield of cucumbers was increased, and the growth rate of several potted plants was increased. These investigations have resulted in a quantitative foundation for the potentials of diffuse light in Dutch horticultural greenhouses and the selection and verification of technological methods to convert direct sunlight into diffuse light.
Available from: PubMed Central
- "These changes directly or indirectly influence plant processes. Recently diffuse glass has become available that increases the diffuseness of light without affecting light transmission in the greenhouse (Hemming et al., 2007, 2008, 2014). "
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ABSTRACT: Plants use diffuse light more efficiently than direct light, which is well established due to diffuse light penetrates deeper into the canopy and photosynthetic rate of a single leaf shows a non-linear response to the light flux density. Diffuse light also results in a more even horizontal and temporal light distribution in the canopy, which plays substantial role for crop photosynthesis enhancement as well as production improvement. Here we show some of the recent findings about the effect of diffuse light on light distribution over the canopy and its direct and indirect effects on crop photosynthesis and plant growth, and suggest some perspectives for further research which could strengthen the scientific understanding of diffuse light modulate plant processes and its application in horticultural production.
Frontiers in Plant Science 09/2015; 6:704. DOI:10.3389/fpls.2015.00704 · 3.95 Impact Factor
Available from: Akira Tani
- "annuum) under a light diffusion film were higher by 10.9 % and 12 %, respectively , than fruit setting and yield of green pepper under a polyethylene film. Hemming et al. (2008) reported that the yield of cucumber (C. sativus L.) increased in a greenhouse covered with a diffusion film. "
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ABSTRACT: Power generation by roof-mounted photovoltaic (PV) modules may provide additional income to farmers if the crop production is comparable to that under normal greenhouse conditions. However, fluctuating irradiance caused by the partial shade of PV modules has been reported to reduce crop production. In the present study, we have shown for the first time the possibility of improving lettuce growth by using light diffusion films under roof-mounted PV modules. The effects of different light conditions (direct but fluctuating, and diffused but uniform irradiations) under PV modules on the morphology, yield, and photosynthesis of hydroponically grown lettuce were investigated. Lettuce growth was inhibited, resulting in lower dry weight and relative growth rate (RGR) with longer leaves, under the fluctuating light by roof-mounted PV modules compared to that under normal greenhouse conditions. On the other hand, under diffused light conditions, the ratio of leaf width to length increased and the values were comparable to those in the control in spring, summer, and fall cultivations. Although the net photosynthetic rate of fully expanded leaves of lettuce grown under diffused light was lowest, their dry weight and RGR were comparable to the control in summer and fall cultivations. Diffused light might penetrate into the lower layers of the leaf canopy, thereby increasing CO2 fixation of the whole canopy. Our results suggest that the application of light diffusion films is a viable option for improving crop productivity under roof-mounted PV modules.
Journal of Agricultural Meteorology 09/2014; 70(3):139-149. DOI:10.2480/agrmet.D-14-00005
- "In many plant species, the photosynthetic capacity and leaf nitrogen content depend on the prevailing light intensity within the canopy (Anten et al., 1998; Drouet and Bonhomme, 2004). Acclimation to diffuse or direct light also includes acclimation of leaf morphology and anatomy, which affect light absorption and, consequently, photosynthesis (Hemming et al., 2007; Brodersen et al., 2008; Markvart et al., 2010). Furthermore, diffuse light might also decrease leaf temperature and the extent of photoinhibition as fewer local peaks in light intensity occur. "
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ABSTRACT: Background and AimsPlants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation.Methods
Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied.Key ResultsThe highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when global irradiance was high.Conclusions
Diffuse light enhanced crop photosynthesis. A more uniform horizontal PPFD distribution played the most important role in this enhancement, and a more uniform vertical PPFD distribution and higher leaf photosynthetic capacity contributed more to the enhancement of crop photosynthesis than did higher values of LAI.
Annals of Botany 04/2014; 114(1). DOI:10.1093/aob/mcu071 · 3.65 Impact Factor
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