Supplemental LED Lighting Research Articles

Nitrate content in Valerianella locusta L. plants is affected by supplemental LED lighting

Nitrate concentration in edible parts of plants is still at the center of interest. Nitrate metabolism in plants is regulated among others by light. Therefore, the effect of LED and HPS lamps, as supplemental to solar radiation, on nitrate concentration and metabolism in Valerianella locusta ‘Nordhollandse’ was tested (in 30th and 60th day of lighting, at noon and evening hours). In two years of study, in autumn and winter, nitrate content decreased significantly in lamb’s lettuce grown under 90% red+10% blue LED light in comparison to HPS treated plants. The highest decrease (by about 1600mg NO3−kg−1 fresh weight) was observed in 60th day of lighting, in winter, during irradiation (in the evening). We recommend just this combination of LED light for lamb’s lettuce in the greenhouse cultivation. Nitrate reductase activity (NRA) was affected to a greater extent by the length of vegetation than by the light treatment. On average, after 30days of lighting in V. locusta leaves, levels of NRA activity and nitrates were higher (about 25% and 40%, respectively) in comparison to 60days of treatment. Our results indicate the need for extension of similar research on other species that can potentially accumulate high amounts of nitrate in greenhouse crop production.

Effects of LED light on the production of strawberry during cultivation in a plastic greenhouse and in a growth chamber

This study was aimed at investigating the production of phytochemicals that determine fruit quality, and evaluating growth characteristics of mature strawberry plants during cultivation under three different wavelengths (blue, red and blue plus red) of LED light. Cultivation was conducted in two separate locations, namely, a growth chamber (GC) illuminated with LED lights as the sole light source and a plastic greenhouse (PG) which was given supplemental LED light in addition to ambient light. It was noted that leaves of plants cultivated in the GC under LED lights displayed elevated levels of chlorophyll compared with those cultivated in the PG. In contrast, plants cultivated in the PG with supplementary LED lights yielded much higher production of fruits than those cultivated in the GC. Moreover, fruits harvested in the PG were demonstrated to contain higher levels of organic acids than those harvested in the GC. When the effects of different LED lights were examined, a remarkably higher production of fruits was achieved in the PG when ambient light was supplemented with either blue LED light or combined blue and red LED light. Furthermore, it was also noted that greater accumulation of organic acids and phytochemicals such as phenolic compounds were observed in the fruits that had been cultivated in the PG when ambient light was supplemented with either red LED light or combined blue and red LED lights.

Production and Financial Analyses of the Rotating Living Wall, an Urban Agricultural System

Experiments were performed from June 2014 to May 2015 at Penn State University’s greenhouse facilities in order to understand the production capacities and financial viability of an innovative growing system referred to as the Rotating Living Wall produced by GreenTowers, a student innovation/entrepreneurship team. The system is a six-foot vertical conveyor that rotates troughs of microgreen plants to achieve even distribution of sunlight as well as relatively low maintenance within a minimal square foot area. Experiments were performed to understand differences in seasonal yields, differences in yields based on variety of microgreen, yield comparison to a traditionally grown microgreen control group; both on a yields per/trough method as well as a yields per/ft.2 method, rotational timing, moving versus stationary growth, differences in growth based on media depth, and differences in production yields from supplemental lighting. Performance criteria were based on measuring fresh weight, dry weight, height, and SPAD-meter readings (soil plant analysis development). Differences in yields throughout seasons were significant as well as differences between the Rotating Living Wall systems compared to a control group of traditional static greenhouse benches. The use of LED supplemental lighting provided significant differences in yields throughout winter season growing. Rotational timing, media depth, and physical movement of plants showed minimal or no significant influence on yields. By establishing the potential revenues and costs that were part of growing with the Rotating Living Wall system, financial viability was analyzed showing that these systems could be profitable when utilized in State College, PA, within certain operating parameters. The research completed throughout these studies has not only provided a baseline of operation for the systems but has also shown potential for the development of urban agricultural systems capable of aiding in the elimination of “food deserts” or urban neighborhoods and rural towns with limited food access.

LED 광질이 칼랑코에의 생육과 개화에 미치는 영향

This study was conducted to examine the effect of LED light quality and supplemental LED light on growth and flowering for potted flowering plant of Kalanchoe. 1. Plant height of Kalanchoe was enhanced under Red, regardless of treatment time. 2. Root length and stem diameter of Kalanchoe were enhanced by Red+Blue. 3. The number of internodes was not influenced by LED light quality. Length of flower stalk of Kalanchoe increased under Red+Blue, but treatment time did not result in statistically significant differences. 4. Leaf area was not influenced by LED light quality in Kalanchoe. 5. The number of flower buds and open flowers was decreased by LED light treatment, but days to flowering was reduced by Red+Blue for 4 hr after sunset in Kalanchoe. 6. Chlorophyll and anthocyanin content was not significantly affected by LED light treatment, but anthocyanin content tended to increase by Blue 4 hr after sunset. 7. Fresh and dry weight did not increased by LED light treatment in Kalanchoe.

Investigation of Supplemental Lighting with Different Light Source for High Yield of Strawberry

Although supplemental lighting has been successfully used to boost greenhouse vegetable production, it has not found wide application in forced strawberry cultivation. In this study, we examined the effect of supplemental lighting from two different light sources on strawberry growth and yield. Strawberry plants were exposed to LED or fluorescent lamp illumination for 12 hours (6:00-18:00) daily from January to April. Under LED illumination, PPFD values greater than 400 μmol m -2 s -1 were recorded at leaf heights of 10-30 cm, and leaf photosynthetic rates in plants exposed to LED supplemental lighting were much higher than in controls and plants exposed to fluorescent light. This accelerated photosynthesis promoted plant growth, as manifested by increases in leaf dry weight, leaf area, and specific leaf weight, leading in turn to significant increases in average fruit weight, number of fruits, and marketable yield. The higher yields observed in LED-exposed plants compared with those under fluorescent lamp illumination were due to comparatively higher LED light intensities. These results suggest that supplemental lighting using higher irradiance LED is an effective method for high yield production during forced strawberry cultivation.

KNU 식물공장의 냉난방 에너지 부하 해석에 관한 연구

The heating and cooling energy load of the KNU plant factory was analyzed using the DesignBuilder. Indoor temperature set-point, LED supplemental lighting schedule, LED heat gain, and type of double skin window were selected as simulation parameters. For the cases without LED supplemental lighting, the proper growth temperature of lettuce 20℃ was selected as indoor temperature set-point together with 15℃ and 25℃. The annual heating and cooling loads which are required to maintain a constant indoor temperature were calculated for all the given temperatures. The cooling load was highest for 15℃ and heating load was highest for 25℃. For the cases with LED supplemental lighting, the heating load was decreased and the cooling load was 6 times higher than the case without LED. In addition, night time lighting schedule gave better result as compared to day time lighting schedule. To investigate the effect of window type on annual energy load, 5 different double skin window types were selected. As the U-value of double skin window decreases, the heating load decreases and the cooling load increases. To optimize the total energy consumption in the plant factory, it is required to set a proper indoor temperature for the selected plantation crop, to select a suitable window type depending on LED heat gain, and to apply passive and active energy saving technology.