Tewolde Fasil T, Lu Na, Shiina Kouta, Maruo Toru, Takagaki Michiko, Kozai Toyoki, Yamori Wataru
Graduate School of Horticulture, Chiba UniversityMatsudo, Japan; Center for Environment, Health and Field Sciences, Chiba UniversityKashiwa, Japan.
Center for Environment, Health and Field Sciences, Chiba University Kashiwa, Japan.
Front Plant Sci. 2016 Apr 7;7:448. doi: 10.3389/fpls.2016.00448. eCollection 2016.
Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m(-2) s(-1) measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter.
配备先进环境控制系统的温室，即所谓的太阳光植物工厂，能让种植者实现高品质农产品的高产。在种植密度高的温室作物中，下层叶片的光合光子通量密度（PPFD）较低往往会限制植物生长，尤其是在冬季，此时太阳高度和冠层处的PPFD较低，且白天时长比夏季短。因此，为下层冠层提供补光可以提高全年的生产力。然而，补光成本可能很高。在一些地方，夜间电费较低，但夜间使用补光的效果尚未得到研究。在本研究中，我们研究了白天或夜间进行补充LED间隔补光（以下简称LED间隔补光）对单杆番茄植株在冬季和夏季的光合作用、生长和产量的影响。我们使用了红蓝光组合的LED间隔补光模块，在第一次开花后立即照亮下层叶片。该光在距离LED模块10厘米处测得的PPFD为165 μmol m(-2) s(-1)。白天处理的LED间隔补光时间为凌晨4点至下午4点，夜间处理的时间为晚上10点至上午10点。仅接受太阳光照射的植株用作对照。白天进行LED间隔补光提高了中层和下层冠层叶片的光合能力，在冬季显著提高了27%的产量；然而，夏季的光合能力和产量没有显著增加。夜间LED间隔补光在冬季和夏季均提高了光合能力，冬季产量提高了24%，夏季提高了12%。此外，冬季夜间LED间隔补光显著提高了番茄果实的总可溶性固形物和抗坏血酸含量，分别提高了20%和25%。夜间使用LED间隔补光也比白天补光更具成本效益。因此，与白天相比，夜间LED间隔补光在夏季和冬季均能以更低的能源成本有效改善番茄植株的生长和产量。
