The optimal photosynthetic photon flux density (PPFD) and seeding density (SD) combinations for microgreens production on vertical farming systems remain unclear for many species. This study aimed to determine the effects of PPFD (50, 100, 150, and 200 µmol m−2 s−1) and SD for sunflower (1275, 1700, and 2125 g m−2), radish (272, 340, and 408 g m−2), and green and red cabbage (126, 180, and 235 g m−2) microgreens. PPFD had no effect on the yield of sunflower, radish, or red cabbage, indicating that 50 µmol m−2 s−1 was sufficient to meet plant demands. Green cabbage yield increased ~10% at 150 µmol m−2 s−1. Increasing SD enhanced yields, with gains of up to ~22%, 49%, 52%, and 30% for sunflower, radish, green, and red cabbage, respectively (1700, 408, 235, and 180 g m−2). PPFD did not affect the nutrient content of sunflower, likely due to its high seed reserves. A higher SD increased anthocyanin in red cabbage but diminished its content in all other species. Our findings highlight that SD is more impactful than PPFD on determining yield, at least under low irradiance, in sunflower, radish, and red cabbage microgreens grown on indoor vertical farming systems.

Proper substrate moisture management is essential for producing high-quality seedlings in nurseries. This study aimed to evaluate the morphological and physiological quality of lettuce (Lactuca sativa L.) and tomato (Solanum lycopersicum L.) seedlings subjected to different substrate moisture levels, monitored by weighing lysimetry under protected environment conditions. Four experiments were conducted over two growing seasons (2019 and 2020) using six irrigation treatments corresponding to 80, 70, 60, 50, and 40% of the substrate water-holding capacity, in addition to the conventional irrigation management adopted by the grower (Control). Water consumption, morphological traits, root architecture, gas exchange, chlorophyll fluorescence, and photosynthetic pigments were assessed. Cumulative irrigation water applied ranged from 77 to 92 mm in lettuce and from 91 to 132 mm in tomato. Reducing substrate moisture to 40% negatively affected seedling growth, root development, and physiological performance in both species. In tomato, stomatal conductance decreased by up to 90%, accompanied by a decline in Fv/Fm from 0.78 to 0.70. Both lettuce and tomato tolerated moderate reductions in substrate moisture (60–70% holding capacity) without significant losses in growth or gas exchange performance. However, the highest seedling quality was achieved under the grower-managed Control and the 80% substrate moisture treatment, although the traits contributing to this response differed between species. In lettuce, favorable performance was associated with growth, pigment-related traits, and photochemical efficiency, whereas in tomato superior seedling quality was linked to shoot growth, root development, and gas exchange characteristics. These findings support the use of species-specific irrigation strategies to improve seedling quality in nursery production.

O Brasil vive o ciclo da sojicultura, sendo essa a cultura de maior destaque financeiro para o país, em que seus produtores, em condições de sequeiro, encontram desafios contínuos pelo déficit hídrico enfrentado no decorrer do ano safra, afetando o crescimento e desenvolvimento das plantas, culminando na redução dos níveis produtivos. O silício é um elemento benéfico com uso disseminado principalmente para controle de fatores bióticos, porém apresenta elevado potencial também para auxiliar a planta a superar diversos estresses abióticos, como o estresse hídrico, através de sua ação no metabolismo e fisiologia das plantas, com o fortalecimento das paredes celulares, estímulo à ação da defesa antioxidativa das plantas, atuando como supressor dos fatores de estresse, diante disso objetivou-se esclarecer suas influências no ciclo das culturas, principalmente da soja, que levariam a esse comportamento. Estudos demonstram que diversas culturas podem se beneficiar da aplicação de silicatos, como batata, sorgo, arroz, tendo as plantas caracterizadas como acumuladoras de silício as que apresentam maiores respostas à sua aplicação, em que o elemento pode afetar desde o tempo de prateleira de vegetais até a tolerância a elementos tóxicos, além de potencial mantenedor do desenvolvimento das plantas dentro de certa normalidade em frente a condições climáticas não favoráveis. Contudo, estudos no ramo da soja ainda são escassos e com resultados divergentes, sendo necessárias maiores análises em diferentes cultivares.

The fungus Trichoderma harzianum is a sustainable and environmentally friendly solution for use in agriculture. Its application stimulates the growth of radish microgreens, a short-cycle crop, standing out as an agricultural practice that meets the growing demand for healthier crops. This study aimed to evaluate the use of Trichoderma harzianum on the growth and quality of radish microgreens. The research was conducted in a greenhouse, using a completely randomized experimental design (CRD) with three treatments and eight replications. The treatments included a control, the application of the fungus on the seeds, and the application of the fungus on the substrate. The phytotechnical and post-harvest characteristics were evaluated. The application of the Trichoderma harzianum to the substrate resulted in a 19.75% increase in yield, a 19.87% increase in the conversion of seed mass into fresh mass, a 2.94% increase in the shoot dry mass, a 2.31% increase in water content, and a 28.29% increase in hypocotyl length compared to the control. The use of Trichoderma harzianum proved to be effective in promoting the growth of radish microgreens.

Paclobutrazol (PBZ) is a growth regulator that widely used in horticulture and in the tomato seedling growth to compact the shoots, increase the stem diameter and, root biomass, allowing more tolerance of the seedlings against adverse weather conditions. The objective of this work was to evaluate the rates of paclobutrazol (0, 4, 7, 10 and 13 mg L-1) applied 15 days after sowing by foliar spray on the growth, chemical composition and xylem vessel number of tomato seedlings cultivated in two periods. The PBZ regardless of the application rate reduced the height of tomato seedlings in both growth periods. The basal stem diameter and leaf area were increased with 13 mg L-1 of PBZ. The lignin percentage also increased with 10 and 13 mg L-1 of PBZ as compared to control for both periods. The number of xylem vessel was not affected by PBZ application on the seedlings in the first period. PBZ application at rates of 7 and 10 mg L-1 increased the xylem vessel number in the second period. In general, the application of 13 mg L-1 of PBZ generated seedling more robust to overcome climate adversities.

Abstract Higher seeding densities can negatively affect the yield of microgreens. We quantified the effects of supplemental light quality and seeding density on the yield of microgreens. Seeds of red beet (Beta vulgaris L. ssp. esculenta) were grown in a greenhouse and provided with a narrow‐spectrum (or “purple”) and broad‐spectrum (or “white”) supplemental lighting at nighttime. Purple spectrum contained 90% red, 0% green, 10% blue, and 0% far‐red (R90: G0: B10: FR0) light, and white spectrum had 35% red, 42% green, 23% blue, and 0% far‐red light (R35: G42: B23: FR0). Each light quality treatment contained seeding densities of 50, 150, 300, and 450 g m−2. We measured fresh weight (FW) and dry weight (DW) on days 8, 10, 12, and 14 after sowing, relative growth rate (RGR), canopy area (CA), and chlorophyll (chl)a, chlb, betacyanin, and betaxanthin pigments. The optimal seeding density in the white treatment was 300 g m−2, whereas FW increased even at the seeding density of 450 g·m−2 in the purple treatment. The RGR of seedlings decreased with increasing seeding density but was higher by 27.8% in the purple than white treatment. The slope of the relationship between DW and CA (related to photosynthetic efficiency) was higher for the purple than white treatment (0.012 vs. 0.008 g cm−2). The ratio of chla to chlb (related to photosynthetic reaction center activity) increased by 15% in the purple than white treatment. Therefore, higher optimal density in the purple than white light quality treatment is likely due to increased photosynthetic efficiency of seedlings.

Lettuce is the most cultivated leafy vegetable in hydroponic systems. The biofortification of lettuce with zinc (Zn) can contribute to relieving nutritional deficiencies in socially vulnerable populations. Biofortification is affordable, easy and fast, even in urban areas. Our objective was to evaluate the effect of Zn concentration in nutrient solutions on the production and agronomic biofortification of lettuce cultivars. The experimental design was completely randomized, in a split-plot design, with four replicates. We tested Zn concentrations of 0.3, 1.0, 1.7 and 2.4 mg L-1 in the hydroponic solution and the cultivars 'Vanda' and 'Saladela'. We evaluated plant diameter, number of leaves, fresh and dry mass of the aerial part and root, a chlorophyll index, Zn content and the accumulation of Zn in leaves and roots. 'Vanda' lettuce had the largest diameter, and 'Saladela' lettuce had the most leaves. The fresh mass of the aerial part was higher in 'Vanda' lettuce. For a Zn concentration of 2.4 mg L-1, the Zn contents of the leaves and roots were 733.3 and 2441 mg kg-1 and the accumulations of Zn in the leaves and roots were 931.66 and 4890 mg plant-1, respectively. Zn content and accumulation were higher in 'Saladela' lettuce. FM, DM did not decrease with increasing Zn concentration in the nutrient solution. Agronomically biofortifying the lettuce produced hydroponically using the nutrient film technique was thus possible

Microgreens have a high nutrient density and are beneficial to human health. Even though this class of vegetables have gaining increasing levels of attention in the last year, scientific research on the growth of microgreens in controlled environments under artificial lighting have not been thoroughly characterized. By describing the scientific outputs focused on the impacts of artificial illumination on microgreens, especially from the first two decades of the 21st century, it is therefore possible to detect advancements and research gaps in this research field. This review is divided in two parts: first, a general overview of the scientific production about microgreens; second, a systematic review of scientific studies exploring artificial lighting on the production of microgreens. The overview of scientific production on microgreens and artificial lighting across the Scopus, Web of Science, and Scielo databases, from 2000 to 2021, respectively, indicated three phases, as before 2011 no paper was found: phase 1 (2012 to 2014), six papers; phase 2 (2015 to 2018), fifteen papers; and phase 3 (2019 to 2021), forty-six papers, respectively. Mustard was the most evaluated crop under all production stages. With regard to the second part of this review, studies on artificial lighting with fluorescent lamps (high-pressure sodium light bulbs-HPS), from the supplementation to the replacement of HPS lighting with light emitting diode (LED) lamps, and plant responses with respect to light properties comprise the main works identified. Studies on the distribution of environmental factors under controlled microgreen cultivation present research gaps.

The yield of many ornamental plant species decreases sharply in the fall and winter seasons due to the decrease in solar radiation and temperature. The aim of this study was to verify the response of two Impatiens hybrid hort cultivars Sunpatiens Compact Royal Magenta and Sunpatiens Compact White to LED supplemental light with different ratios of red and blue: 83% red (640-660 nm): 17% blue (460-470 nm), 75% red (640-660 nm): 25% blue (460-470 nm), 67% red (640-660 nm): 33% blue (460-470 nm), and 50% red (640-660 nm): 25% red (620630 nm): 25% blue (460-470 nm); and control (only natural light). Plants were grown in a nursery greenhouse at Atibaia, SP, Brazil, with day and night air temperature of 28 degrees C and 21 degrees C, respectively. Mother plants were grown with a spacing of 12 cm x 14 cm in plastic boxes (36 cm width x 56 cm length x 14 cm height) with 50% vermiculite and 50% perlite. Lights were placed at 1 m distance from the plants base, emitting a PPFD of 150 mu mol m- 2 s- 1. The daily supplemental light for 12 hours (6 am to 6 pm) began after mother plants transplant and was maintained for seven months until the end of the experiment. The yield and quality of both mother plants and cuttings collected from them, as well as of the plugs developed after three weeks were evaluated regarding to biometric characteristics, pigments, antioxidant enzymes, stress indicators, photosynthetic activity and trichomes counting. Impatiens response varied according to the growing season. In the winter season, at 202 DAT, the 83R:17B LED light increased in 35.4% the number of cuttings produced per plant compared to the control. The light supplementation with different spectral proportions did not cause oxidative stress of the Impatiens mother plants, maintaining its quality. The performance of Royal Magenta cv. differed from the White cv. regarding to the use of artificial lighting, mainly due to the higher concentration of anthocyanin in leaves of the Royal Magenta cv. The supplemental light effect during the cuttings production of the White cv. continued until the final phase of the plugs production, due to more compact cuttings produced in the 83R:17B LED light treatment.

The Brazilian flora is one of the richest in biodiversity and has many species with high pharmaceutical and nutraceutical potential. Among these species is ora-pro-nobis (Pereskia aculeata Mill.), which stands out for the high protein content found in its leaves. The exogenous application of amino acids in crop production has shown promising results, such as the increase in productivity and plant quality, besides their capacity in alleviating environmental stress in plants. Exogenous application of L-arginine (0, 0.25, 1.0 and 2.0 g L−1 of water) was performed by drenching on coconut fiber growing media of ora-pro-nobis plants. Plant growth parameters analyzed were chlorophylls and carotenoids contents, crude protein content, and determination of enzymes and oxidative stress substances. The higher concentration of L-arginine (2 g L−1 of water) increased net photosynthetic rate, leaf area, plant fresh and dry mass, carotenoids content and crude protein content in leaves. Thus, the exogenous application of L-arginine in ora-pro-nobis plants can improve both the productivity and nutritional value of its leaves.

Heat stress can impact crop development and yield and amino acids play diverse essential roles in plants. This work aimed to study the long-term effects of foliar spray with L-arginine in antioxidant machinery, physiology, nutrition, productivity and fruit quality of tomato plants subjected to transient heat stresses. Six concentrations of L-arginine were sprayed on the plants: 0 (control), 0.10, 0.25, 0.50, 1.0 and 2.0 g.L-1. The content of hydrogen peroxide (H2O2), a reactive oxygen species, decreased concurrently to the increasing arginine concentration. The ascorbate peroxide (APX) activity had an inverse behavior to that observed for H2O2 content (r = -0.79), not only indicating that arginine is able to modulate APX, but also suggesting that this enzyme plays an important role on the mitigation of H2O2 generation under heat stress. Ascorbate peroxide and catalase (CAT) activities had a positive correlation (r = 0.82), showing that these enzymes may work in tandem. The influence of arginine on photosynthesis activity and gas exchange was generally weak and depended mainly on the plant developmental stage. Yield was increased by 19.8 and 23.1% in plants that received 1.0 and 0.5 g.L-1 of arginine, respectively, when compared to control plants. In conclusion, the use of exogenous L-arginine can protect tomato plants against oxidative imbalance under transient heat within protected environments.

ABSTRACT Supplemental lighting is becoming a common practice for horticultural greenhouse industries, especially at high-latitude countries. However, no scientific reports were found on this topic in tropical climate countries. This study investigates the effects of LED-interlighting and grafting on photosynthetic response and yield and quality of mini cucumber (hybrid Larino). The experiment took place from April to August in a greenhouse located at a Cwa climate type in Piracicaba (SP), Brazil (22°42’S; 47°37’W; 541 m altitude). The experiment was arranged in completely randomized block design composed of three types of seedlings (ungrafted hybrid, hybrid grafted onto rootstock cultivar Keeper and hybrid grafted onto rootstock cultivar Shelper) and two environments related to light condition (LED supplemental light and natural light as control). The LED devices were placed horizontally at 15 cm from the plants and at 1,5 m height from the floor. The LEDs emitted a photon flux of 220 µmol m-2 s-1 by red light (80%) with a peak wavelength of 662 nm and blue light (20%) with a peak wavelength of 452 nm. Lighting was used for 12 h d-1 from 30 days after seedling transplanting until the end of the growth period. The air temperature and relative humidity (RH) were maintained at 23.5±4°C and 72±10% during the light period, respectively. At night, average temperature was 18.6±5°C and the RH was 90±5%. The LED-interlighting treatment increased in 40% the plant CO2 net assimilation rate compared to plants grown under natural light in the greenhouse. Plants grafted onto both rootstocks had higher CO2 net assimilation rate (µmol CO2 m-2 s-1), apparent carboxylation efficiency (µmol CO2 mol air-1) and apparent electron transport rate (µmol electrons m-2 s-1) than non-grafted ones. The early yield increased 11.6% and 24% in response to LED-interlighting and grafting, respectively. The commercial yield also increased with LED light at rate of 13% but did not enhance with grafting. Postharvest quality parameters as titratable acidity, total soluble solids and shelf life were not affected by the LED light supplementation. Our study shows that even in tropical climate conditions LED-interlighting can be used as a tool to improve commercial cucumber production.

Polyhalite (PH), a naturally occurring multinutrient fertilizer containing potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), has improved tomato (Solanum lycopersicum L.) production in Brazil but a specific response by tomato to the S in PH is not confirmed. We compared four S sources - PH, sulfate of potash (SOP), sulfate of potash magnesia (SOPM), and single super phosphate (SSP) - applied at a target application rate of 40 kg S ha(-1) to fertilizers with no S (muriate of potash, MOP), and no K or S at commercial application rates in three commercial fields in Brazil with nitrogen (N), phosphorus (P), and K applied at recommended rates of 355, 500, and 200-300 kg ha(-1), respectively. Consistent across locations, PH increased total yields over the control, MOP, and SSP, with SOP and SOPM higher than the control but not MOP or SSP. Only PH increased marketable yields compared to the control. Yields increased linearly with fruit numbers per plant which were higher for PH than the control or MOP, indicating higher fruit set in PH contributed to yield differences. While fertilizers increased leaf K and S concentrations and soil test K and SO4-S, yield differences did not appear to be related solely to either K or S fertilization, nor to Mg fertilizers to which there was no response. Leaf and fruit Ca concentrations were higher in PH than the control and MOP at some locations suggesting Ca improved fruit set in PH. Results suggest tomato likely responded to the multinutrient content or solubility pattern of PH.

Soybean is one of the most important crops of economic value, and among the factors that can alter its productivity is the water-deficit. Studies show that amino acids such as proline and glutamate can help protect plants against abiotic stresses, such as water restriction. Therefore, the present study aimed to investigate the improvement of tolerance to water deficit in soybean plants when submitted to the application of proline and glutamate. The application of these amino acids was carried out as seed treatment (ST) or as foliar application (FA). Three irrigation levels (80, 60, and 40% of the pot field capacity) were used, which corresponded to treatments without water deficit, moderate, and high deficits, respectively. The high water deficit provided a significant reduction in plant growth and productivity. Under these conditions, glutamate as ST was effective in increasing the plant dry mass and yield (21% increase in relation to control). In plants without water restriction, the application of glutamate as ST reduced the lipid peroxidation and increased the dry mass of the plants, volume, and root projection area (PA). On the other hand, for plants submitted to the low water deficit, the FA of proline increased the dry mass of the plants, nitrate reductase, and PA. Therefore, in soybean plants without water restriction and with high water deficit, the best response was obtained with glutamate as ST. For plants submitted to low water deficit, the best procedure was the application of proline as FA.

Nitrogen (N) is the most important nutrient in crop productivity and silicon (Si) increases the uptake of nutrients and affect the uptake of N. The objective of this study was to evaluate the effect of Si combined with rates of N on the growth, root development, uptake of N and Si, assimilation of N, and photosynthesis of the tomato plants (Solanum lycopersicum). A factorial 3 × 3 was used, with rates of Si 0 (control treatment), 1, and 3 mmol L–1, and rates of N 5 (control treatment), 15, and 25 mmol L–1 in the nutrient solution. The rates of N did not affect the dry mass production and uptake of Si. However, the application of Si improved the plant growth and accumulation of Si and N. Relating to control treatment, the rate of Si 1 mmol L–1 increases the dry mass production and accumulation of Si and N in order of 52, 37, and 54 %, respectively. Although the rate of N did not increase the plant growth, it was verified that the N 15 mmol L–1 improves the concentration and accumulation of N in the shoots, and the relative concentration of chlorophyll with values of 43.5, 67, and 14 %, respectively, compared to the control. The supply of Si under low and high availability of N improved the glutamine synthetase, but at the rate of N 25 mmol L–1, a decrease in the transpiration rate and stomatal conductance was verified. Under the high availability of N, the glutamine synthetase raised 78 % as an effect of Si 3 mmol L–1 compared to control treatment (Si 0 mmol L–1). Nevertheless, the transpiration rate and stomatal conductance decreased 49 and 52 % under that condition. The excess of N 25 mmol L–1 negatively affected the root development, but under that condition, the application of Si increased the root length, root surface, and root hood in order of 70, 40, and 77 % compared to the control treatment. Application of Si is recommended for tomato growth, especially when cultivated with high N availability. The application of silicon enhances the plant growth, root development, nutrient uptake, nitrogen assimilation, and photosynthesis of the tomato plants cultivated under rates of N. We recommend the use of Si 3 mmol L–1 and N 15 mmol L–1 for the tomato plants under the nutrient solution

Tomato (Solanum lycopersicum L.) grown in the state of Sao Paulo represents 21.5 % of the total production in Brazil, making it the top table tomato-producing state in the country. Tomato cultivation in greenhouses is becoming increasingly popular in Brazil, as crop plants are protected against pests and unfavorable weather. However, issues regarding elevated greenhouse temperatures are common and can severely impact tomato yield due to the deregulation of vital plant functions, leading to the generation of toxic reactive oxygen species (ROS) and oxidative stress. Since endogenous proline accumulation has been correlated with heat stress relief due to ROS elimination and protection of cell structures, we evaluated the effects of foliar applications of L-proline at rates ranging from 0 to 1600 mg L-1 onto photosynthetic parameters, antioxidant system enzymes, malonaldehyde and hydrogen peroxide contents, post-harvest characteristics, and productivity of tomato plants subjected to high temperatures during the growth cycle. Regardless of rate, L-proline applications resulted in lower hydrogen peroxide contents despite no increase in antioxidant enzymes' activity, and improved titratable acidity (TTA) as well as the overall fraction of average total soluble solids (TSS) by TTA (i.e. TSS/TTA). L-proline applied at 50 and 100 mg L-1 increased commercial and total fruit yield per plant. The 100 mg L-1 rate also enhanced the plants' water use efficiency while decreasing malonaldehyde content, further indicating that exogenous applications of L-proline at the optimal rate of 100 mg L-1 can aid in alleviating high temperaturerelated damage to greenhouse-grown tomato plants.

Fertilizer management is an essential step in the production process, as it allows the plant to use its productive capacity to the fullest extent possible. Researchers have tested maximum nutrient use with reduced losses to the environment aiming to increase productivity with fewer environmental impacts. This study compared the effects of controlled-release fertilizers (CRFs) with water-soluble fertilizer (WSF) and clear water (control) on the growth and nutrient uptake of croton (Codiaeum variegatum L.) and nitrogen leaching. The experiment was conducted with three replications and six treatments: two rates (1.5 g and 3.0 g per liter of substrate) of two CRFs [Osmocote Plus (15% N, 3.93% P, and 9.96% K) and Basacote (15% N, 3.49% P, and 9.96% K)], WSF, and clean water as control. All CRFs were applied before planting and WSF was supplied as nutrient solution through automated moisture sensor activated irrigation system. Plant growth (number of leaves, leaf area, stem height, root volume, and shoot and root dry weights) and total nutrient contents in the leaf tissue were evaluated every 30 days. Electrical conductivity (EC), pH, nitrate, ammonium, and total nitrogen contents were measured in the leached solution. Indeed, results showed that CRFs at a low rate provided similar development and quality of croton plants compared with WSF. Plant growth indicators were similar until 90 days after transplanting (DAT). After that, at 150 DAT, the highest values to number of leaves and leaf area occurred with WSF and with the lowest CRF rate as compared with the other treatments and control. The highest root volume was found with the WSF, which resulted in larger roots compared with the other treatments. These results showed WSF can be replaced by CRFs at low rates on croton growth. Moreover, according to the visual scale, the best treatments were WSF and Basacote at the low rate, where plants were bright, with multicolored leaves with prominent orange shades. However, CRFs maintained pH and EC within the recommended range for the growth of croton and reduced the nitrogen leaching from the pots.