Photosynthetic Capacities and Productivity of Indoor Hydroponically Grown <i>Brassica alboglabra</i> Bailey under Different Light Sources

Abstract

A major challenge for growing vegetables in an indoor vertical farming system will be supplying not only sufficient quantity but also quality of light. It has been reported that yield of crops is enhanced under appropriate combination of red and blue light compared with red light alone. This project aims to investigate the effects of different combinations of red and blue. Plants were cultured for a 12-h photoperiod at 210 µmol•m -2 •s -1 photosynthetic photon flux density (PPFD) under different combinations of red (R) and blue (B) light-emitting diodes (LED). The R:B-LED ratios are: 1) 100:0 (0B); 2) 92:8 (8B); 3) 84:16 (16B) and; 4) 76:24 (24B). All combined RB-LEDs significantly increased light-saturated photosynthetic CO2 assimilation rate (Asat), stomatal conductance (gs sat) and productivity compared with those under 0B. Results suggested that 16B was the most suitable combination of LEDs to achieve the highest productivity for B. alboglabra. To further substantiate these results, comparative studies were conducted under equal photoperiod and PPFD among 16B (RB-LED), white LED (RBW-LED) and high-pressure sodium (HPS) lamps. Shoot, root biomass, leaf number, leaf mass per area and Asat were higher in plants under HPS lamps and RB-LED, than under RBW-LED. However, gs sat was lower under RB-LED and RBW-LED, than under HPS lamps. Plants under RB-LED had higher electron transport rate and photochemical quenching but lower non-photochemical quenching than those under RBW-LED and HPS lamps. Thus, these results more conclusively affirmed that 16B was the most suitable light source to achieve the highest photosynthetic capacities. The findings of this study could also be used in vertical farming to achieve the highest productivity of vegetable crops such as B. alboglabra within the shortest growth cycle with reduced energy consumption.

Physiological and agronomic traits of cabbage plants hybrid Fuyutoyo ® sprayed with plant growth regulators

“…The behavior correlated to photosynthetic yield and agronomic potential, for Brassica, was also verified by He et al (2015), in Brassica oleracea var. Alboglabra, evaluating the effects of different combinations of red and blue films.…”

Vertical farming increases lettuce yield per unit area compared to conventional horizontal hydroponics

“…Lettuce was used as a model plant as it is widely grown in hydroponics as a rapidly growing leafy vegetable (Safaei et al 2015) thereby avoiding some of the complexities of changes in crop biomass allocation during the reproductive process (Heller et al 2014). The study was conducted indoors using only artificial lighting, as this is the dominant approach found in most urban vertical farming projects, especially in plant factory designs (Kang et al 2014;He et al 2015) and allows more precise control of environmental conditions (Poorter et al 2012). Our results show that VFS increased lettuce yield per unit area compared to HHS and suggest that variation in light intensity between cropping systems of different spatial orientation could explain differences in crop yield.…”

Impacts of LED spectral quality on leafy vegetables: Productivity closely linked to photosynthetic performance or associated with leaf traits?

“…The 16B is the most suitable combination of RB-LED for Chinese broccoli to achieve the most rapid leaf development with the highest leaf number, total leaf area and leaf mass per unit area (LMA) and greatest stomatal density (SD). Chinese broccoli grown under 16B also had the highest concentration of photosynthetic pigments, soluble and Rubisco proteins on a leaf area basis [21] . Thus, these results more conclusively affirm that 16B is the most suitable light source to achieve the highest photosynthetic capacities.…”

“…LED-integrated vertical farming systems have been developed by our research team for both indoors and greenhouse for different leafy vegetable production [1,2] . We have designed and optimized LED lightings for the cultivation of popular and high-valued leafy vegetables and herbs [1,2,16,[20][21][22][44][45][46][47] . They are Chinese broccoli (B. alboglabra), Na Bai (B. chinensis L.), wild rocket (Eruca sativa), mizuna (B. juncea var.…”

“…Curly kale; Kale Toscano and Borecole red); sweet basil (Ocimum basilicum), red and green Chinese Basil (Perilla frutescens). Generally (but not always) combined RB-LED is more effective than only R-or B-LED lighting in enhancing photosynthesis and thus productivity [20][21][22] .…”