March/April 2020
LR&T essentials
SEED OF AN IDEA Iain Carlile finds that plant cultivation is among the key topics in the (a) latest Lighting Research and Technology papers
Photomorphogenesis of w (b)
Electrical current (A), supply Driver an et al’s paper examines the the Power illuminance range of 10-10,000 lux. This posture and rapid reading of the Chinese voltage (V) use of LED lighting in plant therefore provides a relatively simple formula. text among all of the subjects. growth and development, Bao et al conducted an experiment on 24LEDs specifically, wheat sprouts. youngLights adultscontrol with myopia in both eyes and Iain Carlile FSLL is the immediate past Experiments were undertaken using varying equal refractive power. The subjects undertook president of the SLL and a senior associate at dpa lighting consultants photosynthetic photon flux densities with a reading task of Chinese text under varying a continuous spectrum of light. The result illuminance conditions (3, 30, 300 and 600 lux) of the experiments was that an optimum and text contrast (95 per cent and 45 per cent). Communication RD 485 photosynthetic photon flux density was During the experiment measurements were unit identified. This may enable a reduction of taken of the subjects' reading distance, angle of Lighting Research and irradiance during early development of head tilt, and reading speed. Technology: OnlineFirst cultivated plants with no harm caused to the The results showed that the subjects In advance of being published in the plant, while lowering the energy consumption tended to shorten their reading distance and print version of Lighting Research required for cultivation. increase their head tilt angle when reading at and Technology (LR&T), all papers Power supply Temperature Humidity Also considering the growth of plants, low illuminance, and further, reading speed accepted for publishing are available Degni et al’s paper looks at the impact of the was notably slower at low illuminance and low online. SLL members can gain access Watering light spectrum and photosynthetic photon contrast. The observed effects wereCO found to these papers via the SLL website 2 Climate control flux density of LEDs on the germination and under both of the text contrast levels that (www.sll.org.uk) seedling emergence of okra. The light spectra were tested, but were more pronounced used in the experiments had peaks in the red, at the lower contrast. It was found that an Circadian stimulus – blue or green regions of the visible spectrum. illuminance of 300 lux or greater, coupled with A computation model Temperature Humidity PPFD The authors noted that there were high contrast text, facilitated good reading CO2 with photometric and significant interactions between light spectrum colorimetric quantities Sensors and photosynthetic photon flux density on W Truong, V Trinh and TQ Khanh the mean germination time, germination (c) (d) rate, uncertainty of germination, and seedling Photomorphogenesis of wheat emergence height. The spectrum peaking in sprouts with LED irradiation the red showed a better germination rate and of different intensities less uncertainty than the spectra peaking in T Han, T Astafurova, S Turanov, the blue or green parts of the visible spectrum. A Burenina, A Butenkova, 40 The varying photosynthetic photon flux also E Surnina and D Valiev affected the seedling emergence height. Investigating the influences of light on the Impact of light spectrum and circadian system, Truong et al developed a 20 photosynthetic photon flux computational model of circadian stimulus, density on the germination and using photometric and colourimetric seedling emergence of Okra quantities, rather than spectral power BF Degni, CT Haba, WG Dibi, distribution (SPD). 0 YA Gbogbo and NU Niangoran The computational model uses simple 400 500 600 7 parameters of illuminance and the Effects of illuminance and Wavelengh, nm chromaticity coordinates of the white light contrast on the reading of 0 49 128 192 260 µmol·m–2·S–1 source. Validations of the computational Chinese text by myopes model were undertaken, demonstrating a J Bao, R Tan, J Huo, B Drobe Figure 1. (a) Block diagram of the control system; (b) picture of the ‘‘Phytotron’’ greenhouse; (c) sp good fit with Rea’s quantity CS 2018 results and H Chen unit; spectrumirradiation of the LED irradiation system (d) Specialised for circadian-effective light on humans, with unit for wheat sprouts acceptable errors for white light sources, in (Han et al)
Irradiance, mW/m2
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