Effect of Aquaponic vs. Hydroponic Nutrient Solution, Led Light Intensity and Photoperiod on Indoor Plant Growth of Butterhead, Romaine and Kale (\u3ci\u3eL. sativa, B. oleracea\u3c/i\u3e)

Vertical farming has been proposed as a solution for providing food security for an increasing, urbanized human population. Light-emitting diode (LED) technology has become increasingly affordable and efficient, making it an ideal choice as artificial lighting for indoor farms. Still largely undiscovered parameters are the optimal plant varieties and types of production systems for plant growth, profit, and human nutrition. Aquaponics may be able to provide sustainable animal protein for vertical farms, increasing their ability to provide more substantial nutrition to consumers. This research aimed to better understand vertical farming as a food production system, and to determine if aquaponics can be an appropriate and applicable fit for it. The experiment was a randomized, factorial design with three independent variables: (1) LED photoperiod interval (2) LED-plant distance, and (3) nutrient solution, as well as several dependent variables to assess both plant yield and quality. A 4-tiered shelving unit was constructed for nutrient film technique (NFT) plant production, and treatments were assigned to each row: (1) LED experiment: Row A, 12/12hr reduced photoperiod with adjustable LEDs 4in. above plant surface; Row B, 2/1hr altered photoperiod interval relative to the control; Row C (control), 16/8hr “standard” photoperiod. (2) Nutrient experiment: Row C, aquaponic nutrient solution; Row H, hydroponic nutrient solution. Rows C and H had matched photoperiod and light intensity. Kale from Row A had significantly lower fresh and dry plant yield relative to the control, Row C (p\u3c0.05). Hydroponic romaine, Row H, had significantly higher plant yield relative to aquaponics, Row C (p\u3c0.05). Butterhead yields were not significantly different in any treatments (p\u3e0.05). Future research may implement a larger sample size of only one plant variety, harvest plants earlier, limit light intensity variation, effectively “balance” the aquaponics system, and have more measures of plant “quality.

Effects of light quality on the growth and development of two horticultural crops

The effect of various light environments on the growth of two horticultural crops was investigated. The growth and development of plants is affected by light quality, light periodicity, light quantity, and phototropism. These parameters can be controlled by photoselective filters or shade nets to induce morphological and physiological responses in plants. Two sets of greenhouse experiments were conducted by selectively screening sunlight for two horticultural crops, turfgrass and romaine lettuce (Lactuca sativa L. var. longifolia). Treatments for the turfgrass study included a blue polyester gel filter, 40% black poly-woven fabric, and a combination thereof to create reduced R:FR, reduced PPF, and reduced R:FR plus reduced PPF conditions to reproduce vegetative and neutral shade and observe shade avoidance responses under each treatment. Each shade treatment resulted in longer leaves, symptomatic of shade avoidance responses for both turfgrass species. Bermudagrass (Cynodon dactylon (L.) Pers. 'JSC2009-6') had a strong response to each shade treatment and exhibited a decrease in tillers and leaf count. However, there is little evidence that the reduced R:FR ratio in this study initiated responses in bermudagrass over responses to a reduced PPF. Treatments for the lettuce study included four commercial shade nets: Chromatinet pearl, Chromatinet red, aluminet, and standard black. Applied shade nets (all rated to decrease solar radiation by 30%) significantly reduced PPF from 1033 umol m^-2 s^-1 under ambient light to 617 - 733 umol m^-2 s^-1 under nets. Lettuce grown under pearl-+ shade net had the highest number of leaves. Lettuce grown under aluminet in the summer produced plants with a greater leaf area. Lettuce grown under red shade net had the greatest total dry weight. The results of both studies indicates that managing light quality with photoselective filters and spectrally modified shade nets does impact the growth and development of turfgrass and romaine lettuce

NUTRIENT DELIVERY AND WATER MANAGEMENT FOR PRODUCING LETTUCE (Lactuca sativa L.)FOR BIOREGENERATIVE LIFE SUPPORT SYSTEMS

Space farming for fresh food production is a key requirement for the success of long duration space missions through self-sufficiency and human life sustainment (physical and psychological well-being) in space colonies. Plant production contributes to atmosphere revitalizing, water purification and waste product recycling as well. However, several obstacles have to be overleaped including abnormal environmental conditions, space energy and resources limitations. Therefore choosing the appropriate cultivar is as important as the species selection, since such choice can influence the obtained fresh biomass, water use efficiency (WUE), growing cycle duration, qualitative features and more importantly quality conservation after harvest. So far, several studies have suggested various crop species highlighting the varied response to environmental constraints in a genotype and cultivar dependent manner. The aim of the present study was to evaluate six lettuce cultivars belonging to different groups and with different leaf colors under low and optimal light intensity in order to identify the most promising genotypes for incorporation in controlled life support systems. Then two differently pigmented butterhead Lactuca sativa L. (red and green Salanova) were chosen and assessed in term of morphometric, mineral, bioactive compounds and physiological parameters. Through precise control of the nutrient solution (NS), closed soilless systems effectuate targeted manipulation of plant secondary metabolites that constitute health-promoting components of human daily diet. An NFT system in a controlled-environement growth chamber was presently employed to grow these cultivars for 19 day, under optimal light and to assess the effect of NS macronutrient-based concentration, proportion (Ca/Mg/K) and biofortification (Iron and Selenium) effect on the bioactive profile of red and green-pigmented Salanova. In this study, morphometric analysis, mineral composition, antioxidant activitiy, phenolic acids and carotenoids content where studied for all treatments: (i) full, half- and quarter-strength corresponding to EC 1.5, 0.75 and 0.5 dS m-1 , (ii) Macrocations proportions, (iii) four Fe concentrations in the nutrient solution (0.015 control, 0.5, 1.0 or 2.0 mM Fe) and (iv) six Se concentrations (0, 8, 16, 24, 32, 40 μM as sodium selenite). Baby Romaine plants had a better agronomic performance than the rest of the tested cultivars under low light intensity conditions, indicating a more efficient light harvesting mechanism. As for intrinsic water use efficiency (WUEi), it was the highest for baby Romaine and red oak leaf cultivars, regardless of light regime. Chicoric acid was the major detected compound, followed by chlorogenic, caffeoyl-tartaric and caffeoyl-meso-tartaric acids. The major phenolic compound (chicoric acid) and total phenolic acids were not affected by light intensity, whereas the rest of the detected phenolic compounds showed a varied response to light intensity. Regarding cultivars response, red oak leaf was mostly affected by low light intensity showing the highest content in chicoric acid and consequently in total phenolic acids content, while under optimal light conditions red Salanova exhibited the highest phenolic profile. The main detected pigments were β-cryptoxanthin and violaxanthin + neoxanthin, followed by lutein and β-carotene. All the target carotenoids decreased significantly under low light intensity, with red Salanova having a distinct profile of carotenoids. Red Salanova registered a biomass of 130 g at harvesting (19 DAT), 22.1 % bigger than green Salanova, with a water uptake of 1.42 L during the full growing cycle and a WUE of 91.9 g L-1, 13.8 % higher than the green cultivar. The latter had accumulated more P, K, Ca, Mg and 37.2 % more nitrate than red Salanova that in its turn had higher relative water content, leaf total and osmotic potential and higher SPAD index. Red Salanova as well exhibited at harvest around two-fold greater lipophilic antioxidant activity and total phenols, and around six-fold greater ascorbic acid. On the other hand the half-strength nutrient solution reduced fresh yield of both cultivars by 14%, however, moderate nutrient stress (half-strength NS) boosted red Salanova concentrations of ascorbate, chlorogenic, chicoric, caffeoyl-meso-tartaric and total phenolic acids, and anthocyanins by 266%, 199%, 124%, 251%, 162% and 380%, respectively compared to control full-strength NS. Moreover, red Salanova plants treated with elevated Mg (Solution of high proportion of Mg) contained higher amounts of pigments. Chicoric and chlorogenic acid were the main phenolic compounds in SMg, and SCa and SMg red Salanova plants, respectively. As for the biofortification, thhe percentage of yield reduction in comparison to the control treatment was 5.7%, 13.5% and 25.3% at 0.5, 1.0 and 2.0 mM Fe, respectively. Irrespective of the cultivars, the addition of 1.0 mM and especially 2 mM Fe in the nutrient solution induced an increase in the Fe concentration of lettuce leaves by 20.5% and 53.7%, respectively. No significant effects of Fe application on phenolic acids and carotenoid profiles were observed in green Salanova. However, increasing Fe concentration in the nutrient solution to 0.5 mM triggered a spike in chlorogenic acid and total phenolics in red Salanova lettuce by 110.1% and 29.1% compared to the control treatment, respectively; moreover, increased accumulation of caffeoyl meso tartaric phenolic acid by 31.4% at 1.0 mM Fe and of carotenoids violaxanthin, neoxanthin and β-carotene by 37.0% at 2.0 mM Fe were also observed in red Salanova compared to the control (0.015 mM Fe) treatment. Whereas, leaf selenium content increased significantly with Se application in both cultivars, in particular, the red leaf lettuce accumulated 57% more Se than the green one. Regardless the cultivar, the addition of 16 μM Se in the nutrient solution improved the content of all detected phenolic acids, and at the same dose in red Salanova, a substantial increase in anthocyanins content (184%) was also recorded. In conclusion, cultivation of mixed lettuce cultivars is the most possible scenario for space farming where some cultivars could provide adequate amounts of fresh biomass while others could contribute to covering daily diet requirements in nutrients and health beneficial compounds. Moreover, the high phenolics and ascorbic acid contents of red Salanova represent natural sources of antioxidants to enrich human diet, and more convenient agronomic requirements make it an appropriate cultivar candidate for bio-regenerative life support systems, plus a nutritional eustress constitute effective means to increase phytochemical content and optimize year-round production of lettuce in closed soilless systems. In conclusion, nutrient solution management and biofortification could be used as an effective cultural practice to increase bioactive properties and quality of hydroponically grown lettuce

Modern Seed Technology

Satisfying the increasing number of consumer demands for high-quality seeds with enhanced performance is one of the most imperative challenges of modern agriculture. In this view, it is essential to remember that the seed quality of crops does not improve

Fertilizer and Cultivar Selection of Different Vegetable Crops and Evaluation of Different Ph Buffers in Hydroponics

During the last several decades, the primary objective of research work in soilless culture has been the composition of nutrient solutions and optimization of nutrition for commercial hydroponics. It is necessary that the nutrient solution provided for plants in hydroponic systems must be specific for a particular crop, the growth stage, the climatic conditions, and the substrate and hydroponic system used. Therefore, the objective of our study was to evaluate different one and two bag systems for fertilizers for the production of different types of vegetable crops (lettuce, basil, Swiss chard, sweet pepper, and eggplant). Crops are able to uptake nutrients from the nutrient solution only in a specific pH range (5.5-6.5). Therefore, various pH buffers are used to maintain nutrient solution pH in a specified range. The objective of one of our experiments was to evaluate the effect of alternative pH buffers (pH down, lime juice, and vinegar) on pH maintenance of the nutrient solution and growth and development of lettuce, basil, and Swiss chard. Results indicated that hydroponic producers should select lettuce and basil cultivars based on fertilizer used, while Swiss chard cultivars can be selected based on yield. Hydroponic producers should select fertilizer for sweet pepper cultivation in hydroponics based on yield, while for eggplant more cultivars and fertilizers need to be evaluated for yield differences. For alternative pH buffers, growers can use lime juice as an alternative for pH down for lettuce production but not for basil and Swiss chard.Horticultur

Appraisal of Combined Applications of Trichoderma virens and a Biopolymer-Based Biostimulant on Lettuce Agronomical, Physiological, and Qualitative Properties under Variable N Regimes

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Analysis of Growth Parameters for Crop Vegetables Under Broad and Narrow LED Spectra and Fluorescent Light Tubes at Different PPFs

Several physiological and yield parameters were evaluated in lettuce plants, cv. ‘Trocadero’, while growing at four different photosynthetic photon flux (PPF) (70, 120, 250 and 400 ± 10 µmol m-2 s-1), under four light spectra, white (W), red (R) and blue (B) Light-Emitting Diode (LED) lamps and cool white fluorescent tubes (FL). Yield parameters were also evaluated on spinach, turnip and radish, growing under identical light spectra but using a single PPF (340 ± 10 µmol m-2 s-1). Lettuce development was impaired at PPFs below 250 µmol m-2 s-1 for all tested spectra. At higher PPFs (250 and 400 ± 10 µmol m-2 s-1), for the two broad spectra tested (W LEDs and FL light), no significant differences were registered on all physiological and yield parameters evaluated. On all situations W LEDs performed, at least, as good as the FL light, indicating that actual W LEDs can efficiently replace traditional light sources, with all the inherent benefits, which include significant lower power consumption. For all species, narrow light spectra (R and B LEDs) proved not being able to provide normal plant development. Plants under R LEDs, although presenting, in some situations, a fresh weight higher than those achieved with the broad light spectra, always led to abnormal plant morphology, characterized by expanded petioles and leaf curling. B LEDs, in spite of promoting plant growth with normal morphology, frequently led to a lower number of leaves and consequently to a lower fresh weight

Unravelling postharvest quality in microgreens through modulation of preharvest factors

The relatively brief growth cycle required for microgreens to reach harvest maturity renders genotype selection a key component for this expanding new industry. Important compositional differences were presently characterized across microgreens from 13 species and five botanical families. Nitrate hyper-accumulator microgreens were identified that warrants preharvest measures to suppress nitrate content. Across species, K was the most abundant macro-mineral, followed by Ca, P, Mg, S and Na. Genotypic differences in Na, K and S concentrations were wide while variation in P, Ca and Mg was narrower. Antioxidant capacity assayed in vitro was highest in brassicaceous microgreens. The levels of ascorbic acid present in microgreens were higher than corresponding levels in sprouts, plausibly owing to the presence of photosynthetic hexose precursors absent from sprouts. Genotypic variation in pigmentation was also expressed in terms of chlorophyll and carotenoid concentrations. Lamiaceae microgreens exhibited comparatively higher phenolic content, notwithstanding significant varietal differences. Moreover, alternative phenolics-rich species of microgreens, such as coriander from the Apiaceae were for the first time identified. Qualitative and quantitative determination of phenolic profiles demonstrated the predominance of flavonol glycosides, with the O-glycosides of kaempferol showing more species-related distribution. Principal Component Analysis revealed that the clustering of phenolic profiles reflected microgreens' botanical taxonomy with relative consistency. Such information is critical for selecting new species/ varieties of microgreens that satisfy demand for both taste and health. Further to genotype selection, the targeted modulation of microgreens secondary metabolism through select spectral bandwidths was assessed as a tool to produce phytochemically-enriched microgreens of high functional quality and nutritive value. Analytical data on microgreens' response to different light spectra constitutes a valuable resource for designing future crop-specific spectral management systems. Thus, variation in productivity, nutritive and functional quality of novel microgreens (amaranth, cress, mizuna, purslane) was examined in response to select spectral bandwidths (red, blue, blue-red). Growth parameters dependent on primary metabolism were found most favored by blue-red light's efficiency in activating the photosynthetic apparatus. Nitrate accumulation was higher under monochromatic light owing to the dependency of nitrite reductase on the light-driven activity of PSI, most efficiently promoted by blue-red light. Mineral composition was mostly genotype-dependent, however monochromatic red and blue lights increased K and Na and decreased Ca and Mg concentrations. Lutein, β-carotene, and lipophilic antioxidant capacity were generally increased by blue-red light putatively due to the coupling of heightened photosynthetic activity to increased demand for protection against oxidative stress. Finally, the general response to light treatments was a decrease in polyphenolic constituents, particularly flavonol glycosides, and total polyphenols under blue-red light. Notwithstanding that genotype specificity underlies some of the responses to light treatments summarized above, the current work highlights how selection of genetic background combined with effective light management can drive the production of microgreens with superior functional quality. The choice of growth substrate is critical for the production of high-quality microgreens. Therefore, understanding how the physicochemical properties of natural fiber (agave fiber, coconut fiber and peat moss) and synthetic substrates (capillary mat and cellulose sponge) impact the growth and yield attributes, the nutritive and phytochemical composition and the antioxidant potential of select microgreen species (coriander, kohlrabi and pak choi) wan imperative and novel next step in the present line of research. A key finding of this work, which advances our understanding of the current and future literature on microgreens production and potential bioactive value, is that substrates which combine optimal physicochemical properties, such as peat moss, tend to promote faster growth and higher fresh yields that favor high production turnover; however, this is achieved at the expense of reduced phytochemical content, foremost of polyphenols. Therefore, controlled stress applications (e.g., osmotic stress) on microgreens growing on such media warrants investigation as a means of enhancing phytochemical composition without substantial compromise in crop performance and production turnover. Substrates promoting fast growth (e.g., peat moss) also tend to promote nitrate accumulation in microgreens, especially in brassicaceous species that are known nitrate hyperaccumulators. Therefore, nitrate deprivation practices should be considered for microgreens grown on such substrates in order to minimize consumer exposure to nitrates. Although microgreens have become acclaimed as novel gastronomic ingredients that combine visual, kinesthetic and bioactive qualities, the definition of the optimal developmental stage for their harvesting remains fluid. The ontogenetic stages for harvesting microgreens range from the cotyledonary stage to the emergence of the second true leaf. Their superior phytochemical content against their mature counterparts fueled the subsequent work hypothesis that significant changes in their compositional profile likely take place during the brief interval of ontogeny from the appearance of the first (S1) to the second true leaf (S2). Elucidating this hypothesis will contribute towards the standardization of harvest maturity for the microgreens industry. Microgreens of four brassicaceous genotypes (Komatsuna, Mibuna, Mizuna and Pak Choi) thus grown under controlled conditions, harvested at S1 and S2. They were appraised for yield traits and subsequently examined for mineral, volatile organic compounds, polyphenols, ascorbate as well as hydrophilic and lipophilic pigment concentrations. Analysis of compositional profiles revealed genotype as the principal source of variation for all constituents. The absence of significant growth stage effect on many of the phenolic components identified is consistent with previous findings that post-germination differences in phenolic composition between S1 microgreens and baby leaves are minimal. The response of mineral and phytochemical composition and of antioxidant capacity to growth stage was also limited and largely genotype-dependent. It is, therefore, questionable whether delaying harvest from S1 to S2 would significantly improve the bioactive value of microgreens while the cost-benefit analysis for this decision must be genotype-specific. In terms of yield, the lower-yielding genotypes (Mizuna and Pak Choi) registered higher relative increase in fresh yield between S1 and S2, compared to the faster-growing and higher-yielding genotypes. Although the optimal harvest stage for specific genotypes must be determined considering the increase in yield against reduction in crop turnover, harvesting at S2 seems advisable for the lower-yielding genotypes. As reiterated above, microgreens constitute rudimentary leafy greens that impart gastronomic novelty and sensory delight, but are also packed with nutrients and phytochemicals. As such, they comprise an upcoming class of functional foods. However, apart from bioactive secondary metabolites, microgreens also accumulate antinutritive agents such as nitrate, especially under conducive protected cultivation conditions. As stated above, commercially favorable substrates such as peat moss promote fast growth but also tend to promote nitrate accumulation in microgreens, warranting nitrate deprivation practices in order to minimize consumer exposure to nitrates. In this perspective, nutrient deprivation before harvest (DBH) was examined as a plausible strategy, applied by replacing nutrient solution with osmotic water for six and twelve days, on different species (lettuce, mustard and rocket) of microgreens. DBH impact on major constituents of the secondary metabolome, mineral content, colorimetric and yield traits was appraised. Nutrient deprivation was found effective in reducing nitrate content, however effective treatment duration differed between species with decline being more precipitous in nitrate hyperaccumulating species such as rocket. DBH interacted with species for phenolic constituents. It increased the phenolic content of lettuce, decreased that of rocket and did not affect mustard. Further research to link changes in phenolic composition to the sensory and in vivo bioactive profile of microgreens might be warranted. However, it may be safely concluded that brief (≤ 6 days) DBH can be applied across species with moderate or no impact on the phenolic, carotenoid and mineral composition of microgreens. Such brief nutrient deprivation applications also have limited impact on microgreens' yield and colorimetric traits hence on the commercial value of the product. They can therefore be applied for reducing microgreen nitrate levels without significantly impacting key secondary metabolic constituents and their potential bioactive role. Through step-wise examination and appraisal of critical preharvest factors – ranging from genotype and substrate selection, to spectral management, ontogenetic stage at harvest and nutrient deprivation schemes – the current project contributes to the advancement of our understanding on the role and potential utility of these factors in configuring microgreens' yield, sensory, safety, nutritive and bioactive profile

Growth and nutritional quality of leafy vegetables in soilless culture: effect of nutritional factors

The configuration of the two leafy vegetables: lettuce (Lactuca sativa L.) and spiny chicory (Cichorium spinosum L.) was analyzed in a multi-factorial approach accounting for the effects of cultivars, salinity sources and number of cut. Under increasing level of NaCl in the nutrient solution the yield and growth of baby lettuce decreased with more detrimental effects on the green variety. However, the overall quality of baby lettuce increased at 20 mM NaCl whereas a significant decrease of the nutritional value was recorded at 30 mM NaCl. The CaCl2 treatment adopted in the second experiment was able to increase the nutraceutical properties of baby lettuce in particular the mineral and phenolic profile along with the anitoxidant capacity without a significant decrease crop productivity. The second cut inccured a significant increase in total phenols, vitamin C and anitoxidant activities. The results of the third experiment indicate that the osmotic potential level is the dominant factor for the impact of salinity on C. spinosum, but the salinity source may also play a role. Although differences in dry biomass accumulation due to the salt species were observed only between CaCl2 and the other three salinity sources at the highest salinity level, the recorded metabolic profiles following salt stress exhibited distinct differences depending on both the level and source of salinity. Glutamate, pyroglutamate, L-proline, γ-aminobutyric acid (GABA), and sucrose were signatory metabolites enhanced by salinity stress in C. spinosum, which implies that they may be involved in intracellular osmoprotection mechanisms. For a pratical point of view, the results obtained in our research can help the growers in the crop management of these potential leafy vegetables; they can help the consumer in the knowledge of the overall quality of leafy vegetables under different preharvest factors; and they are a good basement for other researches

Pulsed led light: Exploring the balance between energy use and nutraceutical properties in indoor-grown lettuce

In indoor vertical farms, energy consumption represents a bottleneck for both a system\u2019s affordability and environmental footprint. Although switching frequency (sf) represents a crucial factor in determining the efficacy of light emitting diodes (LED) lighting systems in converting electricity into light, the impact of sf is still underexplored. The aim of this work was to investigate the effect of LEDs sf on the productive and qualitative responses of lettuce (Lactuca sativa L.), also considering the resource use efficiency. Plants were grown for 14 days under red and blue LEDs (215 \u3bcmol m 122 s 121 and 16/8 h light/dark, with a red:blue ratio of 3) characterized by two different sf for the blue diode, namely high sf (850 kHz) and low sf (293 kHz). A fluorescent light (same light intensity and photoperiod) was included. LED sf did not alter plant morphological parameters, including fresh or dry biomass, leaf number, leaf area, or water use efficiency. A low sf increased the energy use efficiency (EUE) by 40% as compared to high sf. The latter enhanced the leaf antioxidant capacity, as a consequence of increased concentrations of caftaric and chicoric acids, isoquercetin, and luteolin, consistent with the upregulation of a few genes related to the biosynthetic pathway of phenolic compounds (4C3H and DFR). The study highlights that different sf may significantly affect the EUE as well as crop nutritional properties