Effects of lighting conditions on growth and quality
Light intensity, light duration and spectral distribution characteristics significantly affect growth, nutritional properties and sensory characteristics of basil. Optimization of basil (Ocimum basilicum L.) production in LED environments - a review summarizes the effects on basil growth and the trends and future prospects for basil production using LED-based horticultural light systems.
Basil is one of the most versatile crops to grow and is suited to both outdoor and indoor cultivation, in greenhouses or vertical farms. Its aromatic and attractive leaves make it a popular choice for consumers and growers alike who benefit from its high profitability margins. Leafy vegetables and culinary herbs are the most common crops grown under intensive indoor cultivation and basil has been used as a test crop in many research studies on growing conditions for indoor farming, particularly on the effects of LED lighting conditions on efficiency and quality improvements.
This review analyses the role of light spectrum, light intensity and photoperiod on vegetative growth, plant physiology, phytonutrient content and sensory properties, with reference to differences in optimal conditions for propagation versus production, leaf production versus essential oil production, and fresh quality versus postharvest quality, with the objectives of maintaining high yields and valuable nutritional quality while minimizing energy cost.
UV-B was found generally to have a negative effect on plant biomass, photosynthetic activity and plant height, but a positive impact on phytonutrient levels (phenolic components, flavonoids, anthocyanins and antioxidant capacity). The most effective wavelength for early vegetative growth was between 420 and 490 nm. Contents of aroma, antioxidant and anti-inflammatory compounds were highest in basil grown under 510-570 nm wavelength. The largest leaves and the highest moisture content were recorded when the wavelength was between 650 and 710 nm.
Rising photosynthetic photon flux density from 100 to 600 µmol/m2/s increased volatile compound (VOC) concentrations but, interestingly, increased VOC concentrations did not correlate with consumer preferences. Basil grown under 400 and 600 µmol/m2/s was more bitter which may have contributed to flavour and aftertaste preferences. Also, basil grown under 600 µmol/m2/s had the lowest scores for appearance and texture.
Fresh produce weight could be maximized by keeping blue content relatively low compared to red (B:R=1:4.75), but taste and flavour scores were significantly better with higher blue content (B:R=1:1.9). However, few studies on sensory properties have been reported, and the results are confounded by the large number of basil subspecies, varieties and forms.
The authors conclude that although the effects of light on plant development and quality interact with numerous other environmental conditions, including nutrients and growing media, in a complex form, optimizing lighting conditions for various growing environments is an achievable goal and ways of manipulating lighting systems for maximum results and minimum costs and energy consumption are described.
For research on basil production under LEDs search: Ocimum and "light emitting diodes"
Reference
Sipos, L.; Balázs, L.; Székely, G.; Jung, A.; Sárosi, S.; Radácsi, P.; Csambalik, L. Optimization of basil (Ocimum basilicum L.) production in LED environments – a review. Scientia Horticulturae (2021) 289 (110486) doi: 10.1016/j.scienta.2021.110486