Modelling Environmental Burdens of Indoor-Grown Vegetables and Herbs as Affected by Red and Blue LED Lighting

Bridging the Gap: From Photoperception to the Transcription Control of Genes Related to the Production of Phenolic Compounds

Phenolic compounds are a group of secondary metabolites responsible for several processes in plants-these compounds are involved in plant-environment interactions (attraction of pollinators, repelling of herbivores, or chemotaxis of microbiota in soil), but also have antioxidative properties and are capable of binding heavy metals or screening ultraviolet radiation. Therefore, the accumulation of these compounds has to be precisely driven, which is ensured on several levels, but the most important aspect seems to be the control of the gene expression. Such transcriptional control requires the presence and activity of transcription factors (TFs) that are driven based on the current requirements of the plant. Two environmental factors mainly affect the accumulation of phenolic compounds-light and temperature. Because it is known that light perception occurs via the specialized sensors (photoreceptors) we decided to combine the biophysical knowledge about light perception in plants with the molecular biology-based knowledge about the transcription control of specific genes to bridge the gap between them. Our review offers insights into the regulation of genes related to phenolic compound production, strengthens understanding of plant responses to environmental cues, and opens avenues for manipulation of the total content and profile of phenolic compounds with potential applications in horticulture and food production.

The Effects of Light Spectrum and Intensity, Seeding Density, and Fertilization on Biomass, Morphology, and Resource Use Efficiency in Three Species of Brassicaceae Microgreens

Light is a critical component of indoor plant cultivation, as different wavelengths can influence both the physiology and morphology of plants. Furthermore, fertilization and seeding density can also potentially interact with the light recipe to affect production outcomes. However, maximizing production is an ongoing research topic, and it is often divested from resource use efficiencies. In this study, three species of microgreens-kohlrabi; mustard; and radish-were grown under five light recipes; with and without fertilizer; and at two seeding densities. We found that the different light recipes had significant effects on biomass accumulation. More specifically, we found that Far-Red light was significantly positively associated with biomass accumulation, as well as improvements in height, leaf area, and leaf weight. We also found a less strong but positive correlation with increasing amounts of Green light and biomass. Red light was negatively associated with biomass accumulation, and Blue light showed a concave downward response. We found that fertilizer improved biomass by a factor of 1.60 across species and that using a high seeding density was 37% more spatially productive. Overall, we found that it was primarily the main effects that explained microgreen production variation, and there were very few instances of significant interactions between light recipe, fertilization, and seeding density. To contextualize the cost of producing these microgreens, we also measured resource use efficiencies and found that the cheaper 24-volt LEDs at a high seeding density with fertilizer were the most efficient production environment for biomass. Therefore, this study has shown that, even with a short growing period of only four days, there was a significant influence of light recipe, fertilization, and seeding density that can change morphology, biomass accumulation, and resource input costs.

Variation in supplemental lighting quality influences key aroma volatiles in hydroponically grown 'Italian Large Leaf' basil

The spectral quality of supplemental greenhouse lighting can directly influence aroma volatiles and secondary metabolic resource allocation (i.e., specific compounds and classes of compounds). Research is needed to determine species-specific secondary metabolic responses to supplemental lighting (SL) sources with an emphasis on variations in spectral quality. The primary objective of this experiment was to determine the impact of supplemental narrowband blue (B) and red (R) LED lighting ratios and discrete wavelengths on flavor volatiles in hydroponic basil (Ocimum basilicum var. Italian Large Leaf). A natural light (NL) control and different broadband lighting sources were also evaluated to establish the impact of adding discrete and broadband supplements to the ambient solar spectrum. Each SL treatment provided 8.64 mol^.m^-2.d^-1 (100 µmol^.m^-2.s^-1, 24 h^.d^-1) photon flux. The daily light integral (DLI) of the NL control averaged 11.75 mol^.m^-2.d^-1 during the growth period (ranging from 4 to 20 mol^.m^-2.d^-1). Basil plants were harvested 45 d after seeding. Using GC-MS, we explored, identified, and quantified several important volatile organic compounds (VOCs) with known influence on sensory perception and/or plant physiological processes of sweet basil. We found that the spectral quality from SL sources, in addition to changes in the spectra and DLI of ambient sunlight across growing seasons, directly influence basil aroma volatile concentrations. Further, we found that specific ratios of narrowband B/R wavelengths, combinations of discrete narrowband wavelengths, and broadband wavelengths directly and differentially influence the overall aroma profile as well as specific compounds. Based on the results of this study, we recommend supplemental 450 and 660 nm (± 20 nm) wavelengths at a ratio of approximately 10B/90R at 100-200 µmol^.m^-2.s^-1, 12-24 h^.d^-1 for sweet basil grown under standard greenhouse conditions, with direct consideration of the natural solar spectrum and DLI provided for any given location and growing season. This experiment demonstrates the ability to use discrete narrowband wavelengths to augment the natural solar spectrum to provide an optimal light environment across variable growing seasons. Future experiments should investigate SL spectral quality for the optimization of sensory compounds in other high-value specialty crops.

Food production and resource use of urban farms and gardens: a five-country study

There is a lack of data on resources used and food produced at urban farms. This hampers attempts to quantify the environmental impacts of urban agriculture or craft policies for sustainable food production in cities. To address this gap, we used a citizen science approach to collect data from 72 urban agriculture sites, representing three types of spaces (urban farms, collective gardens, individual gardens), in five countries (France, Germany, Poland, United Kingdom, and United States). We answered three key questions about urban agriculture with this unprecedented dataset: (1) What are its land, water, nutrient, and energy demands? (2) How productive is it relative to conventional agriculture and across types of farms? and (3) What are its contributions to local biodiversity? We found that participant farms used dozens of inputs, most of which were organic (e.g., manure for fertilizers). Farms required on average 71.6 L of irrigation water, 5.5 L of compost, and 0.53 m² of land per kilogram of harvested food. Irrigation was lower in individual gardens and higher in sites using drip irrigation. While extremely variable, yields at well-managed urban farms can exceed those of conventional counterparts. Although farm type did not predict yield, our cluster analysis demonstrated that individually managed leisure gardens had lower yields than other farms and gardens. Farms in our sample contributed significantly to local biodiversity, with an average of 20 different crops per farm not including ornamental plants. Aside from clarifying important trends in resource use at urban farms using a robust and open dataset, this study also raises numerous questions about how crop selection and growing practices influence the environmental impacts of growing food in cities. We conclude with a research agenda to tackle these and other pressing questions on resource use at urban farms.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13593-022-00859-4.

Anion-Exchange Blue Perovskite Quantum Dots for Efficient Light-Emitting Devices

In this study, blue perovskite quantum dots (PQDs) were prepared using didodecyldimethylammonium bromide (DDAB), which can passivate surface defects caused by the loss of surface ligands and reduce particle size distribution. After the passivation of DDAB, blue CsPbClxBr3-x PQDs dispersed in n-octane produced a more compact and uniform PQD thin film than the non-passivated ones. The resulting device showed a stabile lifetime, and an EL peak of 470 nm and a maximum EQE of 1.63% were obtained at an operating voltage of 2.6 V and a current density of 0.34 mA/cm2. This work aims to provide a simple method to prepare blue-emitting PQDs and high-performance PQD-based light-emitting devices.

Red and Blue Light Differently Influence Actinidia chinensis Performance and Its Interaction with Pseudomonas syringae pv. Actinidiae

Light composition modulates plant growth and defenses, thus influencing plant-pathogen interactions. We investigated the effects of different light-emitting diode (LED) red (R) (665 nm) and blue (B) (470 nm) light combinations on Actinidia chinensis performance by evaluating biometric parameters, chlorophyll a fluorescence, gas exchange and photosynthesis-related gene expression. Moreover, the influence of light on the infection by Pseudomonas syringae pv. actinidiae (Psa), the etiological agent of bacterial canker of kiwifruit, was investigated. Our study shows that 50%R-50%B (50R) and 25%R-75%B (25R) lead to the highest PSII efficiency and photosynthetic rate, but are the least effective in controlling the endophytic colonization of the host by Psa. Monochromatic red light severely reduced ΦPSII, ETR, Pn, TSS and photosynthesis-related genes expression, and both monochromatic lights lead to a reduction of DW and pigments content. Monochromatic blue light was the only treatment significantly reducing disease symptoms but did not reduce bacterial endophytic population. Our results suggest that monochromatic blue light reduces infection primarily by modulating Psa virulence more than host plant defenses.

Indoor Vegetable Production: An Alternative Approach to Increasing Cultivation

As the world's population is increasing exponentially, human diets have changed to less healthy foods resulting in detrimental health complications. Increasing vegetable intake by both rural and urban dwellers can help address this issue. However, these communities often face the challenge of limited vegetable supply and accessibility. More so, open field vegetable production cannot supply all the vegetable needs because biotic and abiotic stress factors often hinder production. Alternative approaches such as vegetable production in greenhouses, indoor farms, high tunnels, and screenhouses can help fill the gap in the supply chain. These alternative production methods provide opportunities to use less resources such as land space, pesticide, and water. They also make possible the control of production factors such as temperature, relative humidity, and carbon dioxide, as well as extension of the growing season. Some of these production systems also make the supply and distribution of nutrients to crops easier and more uniform to enhance crop growth and yield. This paper reviews these alternative vegetable production approaches which include hydroponics, aeroponics, aquaponics and soilless mixes to reveal the need for exploring them further to increase crop production. The paper also discusses facilities used, plant growth factors, current challenges including energy costs and prospects.

Effects of Supplemental Light Spectra on the Composition, Production and Antimicrobial Activity of Ocimum basilicum L. Essential Oil

This study was performed to investigate the effects of different supplemental light spectra and doses (duration and illuminance) on the essential oil of basil (Ocimum basilicum L.) cultivated in the net-house in Vietnam during four months. Ten samples of basil aerial parts were hydrodistilled to obtain essential oils which had the average yields from 0.88 to 1.30% (v/w, dry). The oils analyzed using GC-FID and GC-MS showed that the main component was methyl chavicol (87.4−90.6%) with the highest values found in the oils of basil under lighting conditions of 6 h/day and 150−200 µmol·m−2·s−1. Additional lighting conditions caused the significant differences (p < 0.001) in basil biomass and oil production with the highest values found in the oils of basil under two conditions of (1) 71% Red: 20% Blue: 9.0% UVA in at 120 μmol·m−2·s−1 in 6 h/day and (2) 43.5% Red: 43.5% Blue: 8.0% Green: 5.0% Far-Red at 100 μmol·m−2·s−1 in 6 h/day. The oils of basil in some formulas showed weak inhibitory effects on only the Bacillus subtilis strain. Different light spectra affect the biomass and essential oil production of basil, as well as the concentrations of the major components in the oil.

How Much Food Can We Grow in Urban Areas? Food Production and Crop Yields of Urban Agriculture: A Meta-Analysis

Urban agriculture can contribute to food security, food system resilience and sustainability at the city level. While studies have examined urban agricultural productivity, we lack systemic knowledge of how agricultural productivity of urban systems compares to conventional agriculture and how productivity varies for different urban spaces (e.g., allotments vs. rooftops vs. indoor farming) and growing systems (e.g., hydroponics vs. soil-based agriculture). Here, we present a global meta-analysis that seeks to quantify crop yields of urban agriculture for a broad range of crops and explore differences in yields for distinct urban spaces and growing systems. We found 200 studies reporting urban crop yields, from which 2,062 observations were extracted. Lettuces and chicories were the most studied urban grown crops. We observed high agronomic suitability of urban areas, with urban agricultural yields on par with or greater than global average conventional agricultural yields. "Cucumbers and gherkins" was the category of crops for which differences in yields between urban and conventional agriculture were the greatest (17 kg m-2 cycle-1 vs. 3.8 kg m-2 cycle-1). Some urban spaces and growing systems also had a significant effect on specific crop yields (e.g., tomato yields in hydroponic systems were significantly greater than tomato yields in soil-based systems). This analysis provides a more robust, globally relevant evidence base on the productivity of urban agriculture that can be used in future research and practice relating to urban agriculture, especially in scaling-up studies aiming to estimate the self-sufficiency of cities and towns and their potential to meet local food demand.

Ultrasounds and a Postharvest Photoperiod to Enhance the Synthesis of Sulforaphane and Antioxidants in Rocket Sprouts

Ultrasounds (US) and LED illumination are being studied to optimize yield and quality. The objective was to evaluate the effect of a pre-sowing US treatment combined with a postharvest photoperiod including LEDs on rocket sprouts’ quality and phytochemicals during shelf life. A US treatment (35 kHz; 30 min) applied to seeds and a postharvest photoperiod of 14 h fluorescent light (FL) + 10 h White (W), Blue (B), Red (R) LEDs or Darkness (D) were assayed. Antioxidants as phenolics and sulfur compounds (glucosinolates and isothiocyanates) were periodically monitored over 14 days at 5 °C. The US treatment increased the sulforaphane content by ~4-fold compared to CTRL seeds and sprouts. The phenolic acids and the flavonoid biosynthesis were enhanced by ~25%, ~30%, and ~55% under photoperiods with W, B, and R, respectively, compared to darkness. The total glucosinolate content was increased by >25% (W) and >45% (B and R) compared to darkness, which also reported increases of ~2.7-fold (W), ~3.6-fold (B), and ~8-fold (R) of the sulforaphane content as a main isothiocyanate. Postharvest lighting is an interesting tool to stimulate the secondary metabolism, while a US treatment was able to increase the sulforaphane content in seeds and sprouts, although no synergistic effect was reported.

Alterations of Historic Rural Landscape Based on the Multifunctional Approach: The Case of Coastal Fishing Villages in the Yangtze River Basin

The historic landscape is an important component of a village, and the alteration of villages is a necessary process of development. To analyze characteristics of historic rural landscape alterations and the reasons behind them, this study utilized a landscape multifunctional approach and a comprehensive methodology comprising space syntax and field investigations. This study divides the historic rural landscape into two types, ecology-led and production-led patterns, which validate the relationship among ecology, social properties, and cultural connotation in space, offering a new perspective on the alteration of historic rural landscapes. Our findings indicate the interaction among ecology, production, and lives, both diachronically and synchronically, and suggest that it is possible to maintain ecological harmony, functional transformation, and the inheritance of cultural connotation through improving historic rural landscapes.

Combined Effect of Salinity and LED Lights on the Yield and Quality of Purslane (Portulaca oleracea L.) Microgreens

The present work aims to explore the potential to improve quality of purslane microgreens by combining water salinity and LED lighting during their cultivation. Purslane plants were grown in a growth chamber with light insulated compartments, under different lighting sources on a 16 h d−1 photoperiod—fluorescent lamps (FL) and two LED treatments, including a red and blue (RB)) spectrum and a red, blue and far red (RB+IR) LED lights spectrum—while providing all of them a light intensity of 150 µmol m−2 s−1. Plants were exposed to two salinity treatments, by adding 0 or 80 mM NaCl. Biomass, cation and anions, total phenolics (TPC) and flavonoids content (TFC), total antioxidant capacity (TAC), total chlorophylls (Chl) and carotenoids content (Car) and fatty acids were determined. The results showed that yield was increased by 21% both in RB and RB+FR lights compared to FL and in salinity compared to non-salinity conditions. The nitrate content was reduced by 81% and 91% when microgreens were grown under RB and RB+FR, respectively, as compared to FL light, and by 9.5% under saline conditions as compared with non-salinity conditions. The lowest oxalate contents were obtained with the combinations of RB or RB+FR lighting and salinity. The content of Cl and Na in the leaves were also reduced when microgreens were grown under RB and RB+FR lights under saline conditions. Microgreens grown under RB light reached the highest TPC, while salinity reduced TFC, Chl and Car. Finally, the fatty acid content was not affected by light or salinity, but these factors slightly influenced their composition. It is concluded that the use of RB and RB+FR lights in saline conditions is of potential use in purslane microgreens production, since it improves the yield and quality of the product, reducing the content of anti-nutritional compounds.

Postharvest LED lighting: effect of red, blue and far red on quality of minimally processed broccoli sprouts

BACKGROUND

The main objective of this study was to evaluate physiological and quality changes of minimally processed broccoli sprouts illuminated during postharvest storage under blue, red and far-red LED lighting as compared to darkness or illumination with fluorescent light, as control treatments.

RESULTS

Morphological and microbiological changes were determined during 15 days at 5 °C. In addition, total antioxidant activity and bioactive compound changes throughout the shelf life were also monitored. Results showed that far-red LED lighting increased hypocotyl and sprout length, decreased microbial growth and improved the total antioxidant and scavenging activities, compared to darkness and fluorescent lighting treatments. However, it did not stimulate the biosynthesis of phenolic acids. In contrast, blue LED light reduced by 50% the total antioxidant capacity of broccoli sprouts compared to far-red treatment, as well as morphological development. In addition, total scavenging activity was increased under far-red LED light compared with the other treatments by 12-10% (darkness and fluorescence) and 33-31% (blue and red LEDs).

CONCLUSIONS

Our results suggest that minimally processed sprouts may benefit from LED lighting during shelf life in terms of quality, although further experiments should be conducted to optimize a proper exposure cycle and intensity aiming for use in the distribution chain. The results also open the way for further development towards the integration of this technology in the food distribution chain.

Ecosystem Services of Urban Agriculture: Perceptions of Project Leaders, Stakeholders and the General Public

Within the scholarly debate, Urban Agriculture (UA) has been widely acknowledged to provide diverse environmental and socio-cultural ecosystem services (ESs) for cities. However, the question of whether these potential benefits are also recognized as such by the involved societal groups on the ground has not yet been investigated. This paper aims at (1) assessing the perceived ESs of UA, comparing the views of different societal groups in the city of Bologna, Italy (namely: UA project leaders, stakeholders and the general public) and (2) to identify differences in the evaluation of specific UA types (indoor farming, high-tech greenhouses, peri-urban farms, community-supported agriculture, community rooftop garden and urban co-op). In total, 406 individuals evaluated 25 ESs via a standardized Likert-scale survey. The study unveiled similarities and divergences of perceptions among the different societal groups. The statistical analysis indicated that the general public and UA stakeholders agree on the high relevance of socio-cultural ESs, while provisioning ESs was considered as less significant. UA types focusing on social innovation were expected to provide higher socio-cultural ESs whereas peri-urban activities were more closely linked to habitat ESs. We assume that involvement and knowledge of UA are determining factors for valuing the provision of ESs through UA, which needs to be considered for ES valuation, particularly in a policymaking context.

Reaching Natural Growth: Light Quality Effects on Plant Performance in Indoor Growth Facilities

To transfer experimental findings in plant research to natural ecosystems it is imperative to reach near to natural-like plant performance. Previous studies propose differences in temperature and light quantity as main sources of deviations between indoor and outdoor plant growth. With increasing implementation of light emitting diodes (LED) in plant growth facilities, light quality is yet another factor that can be optimised to prevent unnatural plant performance. We investigated the effects of different wavelength combinations in phytotrons (i.e., indoor growth chambers) on plant growth and physiology in seven different plant species from different plant functional types (herbs, grasses and trees). The results from these experiments were compared against a previous field trial with the same set of species. While different proportions of blue (B) and red (R) light were applied in the phytotrons, the mean environmental conditions (photoperiod, total radiation, red to far red ratio and day/night temperature and air humidity) from the field trial were used in the phytotrons in order to assess which wavelength combinations result in the most natural-like plant performance. Different plant traits and physiological parameters, including biomass productivity, specific leaf area (SLA), leaf pigmentation, photosynthesis under a standardised light, and the respective growing light and chlorophyll fluorescence, were measured at the end of each treatment. The exposure to different B percentages induced species-specific dose response reactions for most of the analysed parameters. Compared with intermediate B light treatments (25 and/or 35% B light), extreme R or B light enriched treatments (6% and 62% of B respectively) significantly affected the height, biomass, biomass allocation, chlorophyll content, and photosynthesis parameters, differently among species. Principal component analyses (PCA) confirmed that 6% and 62% B light quality combinations induce more extreme plant performance in most cases, indicating that light quality needs to be adjusted to mitigate unnatural plant responses under indoor conditions.

How Can Innovation in Urban Agriculture Contribute to Sustainability? A Characterization and Evaluation Study from Five Western European Cities

Compared to rural agriculture, urban agriculture (UA) has some distinct features (e.g., the limited land access, alternative growing media, unique legal environments or the non-production-related missions) that encourage the development of new practices, i.e., “novelties” or “innovations”. This paper aims to (1) identify the “triggers” for novelty production in UA; (2) characterize the different kinds of novelties applied in UA; (3) evaluate the “innovativeness” of those social, environmental and economic novelties; and, (4) estimate the links between novelties and sustainability. The study was based on the evaluation of 11 case studies in four Western European countries (Italy, Germany, France and Spain). The results show that the trigger and origin of new activities can often be traced back to specific problems that initiators were intended to address or solve. In total, we found 147 novelties produced in the 11 case studies. More novelties are produced in the environmental and social dimensions of sustainability than in the economic. In most cases, external stakeholders played an important role in supporting the projects. The analysis further suggests that innovativeness enhances the overall sustainability in urban agriculture projects.