Illuminating future food production

: the impacts of tuneable artificial lighting on food crop biology and productivity

Abstract

Challenges to future food production include an increasing world population and increasingly variable and warmer climate. Alternative closed farming systems such as vertical farming allow cultivation in controlled environments for year-round production. Such systems may generate high yields per Ha if a “vertical” model for production is adopted. Light represents one of the main costs for plant factories, and optimisation of the light regime could improve the economics and enhance plant quality. This study investigates how the light environment may be delivered most efficiently to the crop through variation in irradiance, spectral composition, timing and duration of light treatment using a popular lettuce variety. The impacts of light spectra were tested in Lollo rosso at different growth stages. Optimum temperature and light conditions for successful seed germination were identified. Superior yield and quality were produced by LED photosynthetically active radiation (PAR) compared to fluorescent and high-pressure sodium lamps. LED light achieved similar yields from half the energy of fluorescent light. An irradiance response curve for yield and pigment production identified the minimum and maximum PAR thresholds and demonstrated the potential to optimise both characteristics in concert using visible wavebands. Further spectral investigation through the application of supplemental red and blue light treatments illustrated the negative impacts that leaf anthocyanin content has on biomass accumulation. Fast and non-invasive methodologies, such as normalised photochemical reflectance index or chlorophyll a fluorescence were used to follow changes in photoprotection over time. High irradiance supplementation of PAR treatment produced a 4.6-fold increase in leaf anthocyanin content in 2 days. When high energy light treatments were applied to Lollo rosso for long duration (10-15 days), the photoprotective mechanisms changed suggesting the activation of long-term acclimation. Acclimation to more energetic light wavelengths like UV-A supplementation negatively affected plant growth. Blue light supplementation was identified as suitable for short term treatments and was effective in inducing mild photoprotection and enhanced yield and quality traits. Short supplementation with blue at different times of the day produced significantly different responses and demonstrated that supplementation at night produced the best combination of yield and quality improvements.

Date of Award	2020
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Paul Robson (Supervisor)