"Vertical Farming in Hawaiʻi: Design Considerations for our Unique Environment"
Kerry Kakazu, PhD is the President of MetroGrow Hawaii, the first vertical farm in the state. He has a masters and PhD in Plant Physiology from the University of California at Davis. After a career in academia doing research, teaching and administration he combined his interests in plant science, technology and the local food scene to create MetroGrow Hawaii in 2014. The farm has been providing premium leafy greens to local restaurants and gourmet markets since its founding and is now exploring ways to expand vertical farming to significantly increase food self-sufficiency and security in Hawaiʻi.
Foliar Nutrient Concentrations of Strawberry Mother and Daughter Plants Grown in Controlled Environments - Jennifer Boldt Increasing Nutrient Solution Electrical Conductivity Increases Vegetative Growth of Strawberry - Erin Yafuso Impact of Artificial Chilling on Yields of Indoor-Propagated Strawberry Plants in California, Florida, and North Carolina - Ibraheem Olamide Olasupo The Nitrate to Ammonium Ratio Impacts Strawberry Runnering and Daughter Plant Number - Erin Yafuso Effect of Monosilicic Acid on Growth and Physiology of Lettuce - Seunghyun Choi Light Intensity and Zinc Biofortification Effect on Yield and Nutritional Quality of Pea and Radish Microgreens - Pradip Poudel Evaluation of Liquid Organic Fertilizers for Containerized Production of Leafy Greens in a Controlled Environment - Uttara Samarakoon
Few published studies provide foliar tissue nutrient concentrations for strawberry (Fragaria × ananassa) mother and daughter plants. Recommendations primarily focus on tissue concentrations for field-grown plants during fruit production. As controlled environment production of strawberry increases, a need exists to define tissue nutrient concentration ranges for healthy foliar tissue, for both vegetative and fruit production. Defining deficient, sufficient, and toxicity ranges will assist growers in selecting nutrient solution recipes and correcting nutritional issues that arise. The objective of this study was to identify nutrient concentration ranges for healthy strawberry mother and daughter plants grown in controlled environments. Foliar tissue samples were collected from two separate experiments: 1) ‘Albion’, ‘Fronteras’, and ‘Monterey’ grown in a peat-based substrate, and 2) ‘Monterey’ grown indoors in deep water culture. Plants received a modified strawberry nutrient solution (Yamazaki) that provided 100 mg·L-1 nitrogen (N). The percent total N provided as ammonium (NH4 ) ranged from 0% to 40% in both experiments. Plants did not exhibit any visual symptoms of foliar nutrient deficiencies or toxicities. Foliar tissue from mother (n=72) and daughter plants (n=144) were collected and analyzed individually. Nutrient concentration ranges comprised the middle 75% of plant samples (12.5% – 87.5% quantiles). Mother plant macronutrient concentrations ranged from 2.12%–2.64% nitrogen (N), 0.53%–1.23% phosphorus (P), 2.05%–3.88% potassium (K), 2.01%–3.36% calcium (Ca), 0.33%–0.56% magnesium (Mg), and 0.14%–0.28% sulfur (S). Daughter plant foliar macronutrient concentrations ranged from 2.18%–3.38% N, 0.49%–0.92% P, 2.20%–4.19% K, 1.01%–3.03% Ca, 0.31%–0.53% Mg, and 0.15%–0.30% S. Mother plant foliar micronutrient concentrations ranged from 158–233 mg·kg-1 boron (B), 1.5–5.6 mg·kg-1 copper (Cu), 57–587 mg·kg-1 iron (Fe), 131–384 mg·kg-1 manganese (Mn), and 11–29 mg·kg-1 zinc (Zn). Daughter plant foliar micronutrient concentrations ranged from 69–212 mg·kg-1 B, 1.2–4.5 mg·kg-1 Cu, 56–347 mg·kg-1 Fe, 78–315 mg·kg-1 Mn, and 18–36 mg·kg-1 Zn. In general, these macro- and micronutrient ranges overlap between mother and daughter plants. These values represent a first step in developing and refining foliar nutrient ranges for strawberry mother and daughter plants in controlled environments.
Established guidelines for electrical conductivity (EC) for strawberry (Fragaria ×ananassa) fruit production exist for plants grown in soilless substrates. However, EC recommendations for strawberry mother plants may differ when the goal is prolific runnering instead of flowering and fruiting. Our objective was to evaluate the impact of EC concentration strawberry runner and daughter number. Strawberry ‘Monterey’ were grown in a greenhouse in 19.1-cm diameter pots filled with a soilless substrate (50 perlite : 25 coco coir : 25 peat). To formulate the EC treatments, all components of a strawberry nutrient solution (Yamazaki) increased equally, which corresponded to nitrogen (N) concentrations of 50, 100, 150, 200, 300, and 400 mg·L-1 N. After adding 0.8 mM potassium bicarbonate as a buffer and adjusting pH to 5.7, the final nutrient solution EC values were 0.9, 1.6, 2.3, 2.8, 3.9, and 4.9 mS·cm-1. After 12 weeks of treatment, runner and daughter plant number, morphological assessments, and mother plant leaf burn index were evaluated. The qualitative assessment of leaf burn utilized a 1 to 5 scale (1 = no tip burn; 2 = mild, margins of ≥ 3 leaves; 3 = moderate, necrosis on at least half of ≥ 3 leaves; 4 = moderate to severe, complete necrosis on ≥ 3 leaves; and 5 = severe, complete necrosis on ≥ 4 leaves and necrosis of daughter plants). Leaf burn values ranged from 1.6 ± 0.2 (± SE) in the 50 mg·L-1 N treatment to 5.0 ± 0.0 in the 400 mg·L-1 N treatment. Runner number exhibited a quadratic response and ranged from 2 ± 0 at 50 mg·L-1 N to 7 ± 1 at 300 mg·L-1 N. Daughter plant number also exhibited a quadratic response. It increased from 14 ± 3 at 50 mg·L-1 N to 44 ± 4 at 200 mg·L-1 N, then declined to 30 ± 13 at 400 mg·L-1 N. Total plant biomass (mother plant, stolons, and daughter plants) exhibited a quadratic relationship. It increased from 23.5 ± 4.0 g at 50 mg·L-1 N to 65.9 ± 7.9 g at 200 mg·L-1 N, then declined to 40.0 ± 5.2 g at 400 mg·L-1 N. Overall, the optimal nutrient solution EC range for strawberry mother plants was 100 to 200 mg·L-1 N (or 1.6 to 2.8 mS·cm-1). In this range, mother plants produced a high number of runners and daughter plants, with minimal leaf burn due to high substrate EC values.
Unavailability of pathogen-free strawberry propagules in commercial quantities necessitates the development of a novel completely indoor precision propagation technology for the crop, which also seeks to reduce dependence on soil fumigants including methyl bromide. Artificial chilling of plug plants could also enhance transplant vigor, flowering, and yield of strawberry. Under this novel technology, strawberry tips which consisted of five short day (SD) cultivars (Fronteras, Camarosa, Chandler, Sensation and Brilliance) and one long day (LD) cultivar (Monterey) were collected from tissue cultured mother plants. Plants were propagated under completely controlled environment (CE) conditions in a plant factory. Strawberry daughter plants were rooted in 50 cc trays filled with a commercial substrate and were arranged in the controlled environment under 90 – 100 % humidity, 27 °C temperature, 80 – 100 µmol m-2 s-1 light (LED), 18 hours photoperiod, and fertigated using the ebb and flow technique for 28 days. Our hypothesis was that artificial chilling will improve plant vigor and yield of CE-propagated strawberry transplants. We therefore assessed the impact of 350 – 450 hours of artificial chilling on the plant performance and yield of the transplants in four different locations in the US. Monterey, Brilliance, and Sensation cultivars received 350 hours of chilling while Fronteras, Chandler, and Camarosa cultivars were chilled for 450 hours. Strawberry plug plants (chilled and no-chill) were planted in replicated field trials in California, Florida, and North Carolina. Camarosa and Chandler cultivars were transplanted in North Carolina, Fronteras in Southern California, Monterey in Central California, while Brilliance and Sensation were transplanted in Florida. Preliminary results show improved vigor and yield from chilled plants in Florida and North Carolina field trials, while no differences were observed in California. Final results of the study will be shared during the conference.
The use of controlled environments to produce disease-free vegetative clones of strawberry (Fragaria ×ananassa) is increasing. However, protocols for mother plant management that optimize runner and daughter plant number need to be developed. Studies have shown that decreasing the fraction of nitrogen (N) supplied as nitrate (NO3-) can encourage vegetative growth in other crops. Our objective was to identify the %NO3--N that maximized runner and daughter plant number. Strawberry ‘Albion’, ‘Fronteras’, and ‘Monterey’ were grown in 19.1-cm pots filled with a peat-based substrate. Plants were irrigated with a modified strawberry nutrient solution (Yamazaki) that provided a total of 100 mg·L-1 N. The percent of total N supplied as NO3- ranged from 0% to 100%, with the remainder supplied as ammonium (NH4 ). Runners and daughter plants were harvested after eight and 16 weeks of treatment. The impact of %NO3- on cumulative runner number was cultivar specific. ‘Albion’ was not impacted, and the overall mean was 9 ± 1 (± SE).‘Fronteras’ exhibited a quadratic response. It increased from 10 ± 2 at 0% NO3- to 17 ± 2 at 60% NO3-; the calculated maximum runner number was with 64% NO3-. ‘Monterey’ exhibited a linear increase, from 14 ± 1 at 0% NO3- to 22 ± 1 at 100% NO3-. The impact of %NO3- on cumulative daughter plant number was also cultivar specific. ‘Abion’ exhibited a linear increase, from 28 ± 2 at 0% NO3- to 37 ± 10 at 100% NO3- . ‘Fronteras’ exhibited a quadratic response and increased from 19 ± 2 at 0% NO3- to 45 ± 7 at 60% NO3-. ‘Monterey’ also exhibited a quadratic response and increased from 49 ± 4 at 0% NO3- to 90 ± 7 at 80% NO3-. Calculated maximum daughter plant number occurred at 66% and 81% NO3- in ‘Fronteras’ and ‘Monterey’, respectively. Overall, at least 60% NO3- provided robust runner and daughter plant number, but the response depended on cultivar evaluated. ‘Monterey’ and ‘Albion’ appear to prefer a higher %NO3- than ‘Fronteras’ for maximum runner and daughter plant number.
Due to the high operation costs of indoor crop production, improving resource use efficiency to reduce costs has gained importance for sustainability in recent years. Silicon (Si) is not an essential plant nutrient since it is not a component of any structural or metabolic molecule, and plants do not suffer from Si deficiency. However, Si applications have shown beneficial effects on various crops, including improved growth, quality, stress tolerance, and water use efficiency (WUE). This study evaluated the effects of Si on indoor lettuce production to enhance lettuce growth and WUE. Two-week-old lettuce seedlings (Lactuca sativa cv. ‘Green Forest’ and ‘Rouxai’) were transplanted into 5-L deep water culture systems and grown for four weeks in a custom growth chamber with an average temperature/relative humidity of 22.4°C/58.8% and light intensity of 230 µmol/m²/s PPFD. The nutrient solution was weighed and replenished weekly. Si (DUNE™ stabilized monosilicic acid) was applied weekly to plants following two application methods (RA=root application and FS=foliar spray) and three concentrations (Control=0 ppm, C1=264 ppm, and C2=528 ppm). RA C1 significantly improved the shoot fresh weights (FW) and dry weights (DW) of both lettuce cultivars, while FS C1 was less effective than RA. Root growth showed the opposite trend, with FS C1 having the highest root FW and DW of both cultivars. However, root morphology showed cultivar-specific responses, with RA C1 producing the highest root length and surface area in ‘Green Forest’ and FS C1 the highest root surface area and volume in ‘Rouxai.’ WUE was significantly improved by RA C1, RA C2, and FS C2 in ‘Green Forest’ and RA C1 in ‘Rouxai’ compared to the control. Taken together, root application of Si at C1-264 ppm concentration most effectively improved the indoor lettuce growth and WUE.
Zinc (Zn) is a micronutrient crucial for human health, impacting gene expression, cell division, and immune system development. Zinc deficiency affects about 17% of the global population, particularly children, pregnant women, and elderly people, and can lead to disorders and even death. Agronomic biofortification implemented by applying Zn-enriched solutions via fertigation to increase crops Zn content may be a valuable strategy to combat Zn deficiencies. Microgreens, known for their nutrient density, rapid growth cycle, and low phytic acid content, are emerging as promising candidates for Zn agronomic biofortification. However, research is needed to evaluate the effect of factors like light intensity and genotype which can affect Zn accumulation in microgreens. To this purpose, a study was conducted to examine the effect of Zn application rate (0, 5, 10, and 15 mg/L) and light intensity (100, 200, 300, and 400 µmol/m2/s) on yield components, mineral content, and phytochemical profile of pea and radish microgreens. The study revealed that Zn concentration increased with increasing concentration of Zn applied in both species. In peas, a 4-fold increase was observed when applying 15 mg/L of Zn without affecting fresh and dry biomass, while an almost 13-fold increase of Zn content was observed in radish, associated with a 7.8% reduction of fresh biomass and no effects on radish microgreens dry biomass. However, with the increase of Zn content, there was a reduction in Fe concentration in both peas and radish microgreens. The light intensity did not affect Zn content in both species; however, it affected the concentration of macro and other microelements and influenced yield, but the result varied by species. In pea microgreens, low light intensity determined higher fresh biomass but did not affect dry biomass. Instead, the opposite result was observed in radish microgreens; light intensity did not affect fresh yield but increased dry biomass with increasing the level of light intensity applied. Regarding the nutritional profile, total phenols, total antioxidants, and flavonoids increased with increasing Zn concentration and light intensity in both pea and radish microgreens. In conclusion, Zn fertigation effectively enhanced Zn in pea and radish microgreens, and although light intensity had no effect on Zn content, contributed to improve their nutritional profile. These findings provide valuable insights into the production technique of Zn biofortified microgreens and the potential enhancement of their overall nutritional profile using agronomic biofortification techniques.
Organic farming practices, such as the use of organic substrates, fertilizers, pesticides, and biological control, are gaining popularity in controlled environment agriculture (CEA) since soilless production was approved for organic certification in the US. Our past study showed that liquid organic fertilizers are more effective than substrate-incorporated compost fertilizers. Although many liquid organic fertilizers are commercially available, they vary widely in their nutritional composition. Therefore, selection of a suitable fertilizer can be complicated and confusing for CEA growers. The current study aimed to evaluate the effectiveness of different liquid organic fertilizers and compare their performance with that of a synthetic fertilizer for growing lettuce in two different containerized hydroponic systems. Two greenhouse experiments were conducted in a randomized block design with five replicates. In Experiment 1, two types of container (regular container and Dutch bucket) and three fertilizers (earthworm castings and kelp (ECK), molasses with other natural plant extracts (MPE), and hydrolyzed fish protein (HFP)) were considered. The fertilizers were selected from the Organic Materials Review Institute (OMRI) list based on their nutrient profile and reports from other studies. In Experiment 2, selected liquid organic fertilizers (ECK, MPE) were compared with a commercial synthetic fertilizer (CSF). In Experiment 1, ECK performed better, resulting in 28% greater fresh weight, 20% greater dry weight, 48% greater leaf area, 26% greater shoot width, 126% greater average root fresh weight, and 47% greater root length in containerized production compared to the Dutch bucket system. No significant growth difference was observed between MPE and HFP. In Experiment 2, there was no significant growth difference between ECK and CSF; however, the shoot width, leaf area, and dry weight of lettuce were significantly lower with MPE treatments compared to ECK. Results show that ECK performed similarly or better than synthetic fertilizer for growing lettuce in these container hydroponic systems. The findings of this study indicate that a single organic fertilizer could be used instead of several for organic leafy green production in soilless substrate.
Greenhouse supplemental lighting of lettuce and tomatoes to a target light intensity and daily light integral using dimmable LEDs - Neil Mattson Hybrid Model for Forecasting Lettuce Yield in Indoor Vertical Farming - MD SHAMIM AHAMED Development of a pH Management Protocol for Strawberry Mother Plants Grown in Deep Water Culture - Jennifer Boldt Effect of Nutrient Correction Intervals on Nutrient Imbalance, Plant Growth, Yield, and Fruit Quality of Melon (Cucumis melo L.) in a Closed Hydroponic System - Minju Shin Adjusting dissolved oxygen in nutrient solution for optimized kale and arugula growth in hydroponics - Kuan Qin Developing Cardinal Temperatures for Leafy Green Growth and Development Parameters from Constant and Positive Day-Night Temperatures - Sean Tarr Light Intensity Regulates the Interactive Effects between Far-red light and Temperature on Lettuce Growth, Morphology, Photosynthesis, and Secondary Metabolite - Sangjun Jeong
A previously developed algorithm controls on/off decisions for greenhouse supplemental light fixtures and retractable shade curtains to achieve a target daily light integral (DLI). The algorithm, termed LASSI (Light and Shade System Implementation) originally used high pressure sodium (HPS) lights with a 1-hour time step to avoid the warm-up time and reduced lifespan of HPS bulbs when they are frequently turned on/off. We have updated the algorithm accounting for dimmability of light emitting diodes (LEDs) for which light intensity can be adjusted in near real-time (RT LASSI). The objective of this study was to compare performance of lettuce ‘Rex’ and Rouxai’ and tomato ‘Sweetelle’ in response to the LASSI algorithm with HPS fixtures vs. RT LASSI with dimmable white LEDs. Experiments were conducted in adjacent greenhouses and DLI setpoints were 17 mol·m-2·d-1 for lettuce and 25 mol·m-2·d-1 for tomatoes. RT LASSI greenhouses had white LEDs (TSR Grow TG-600 HVR) and LASSI greenhouses had HPS fixtures (PL Light 1000 W). For treatments with RT LASSI, when supplemental lighting was called for, LED treatments were adjusted to complement sunlight to achieve a target instantaneous light intensity of 300 and 400 µmol·m-2·d-1 for lettuce and tomatoes, respective, averaged over a 10 minute interval. For tomatoes a minimum 4-hour dark period was imposed while for lettuce, supplemental lighting could occur anytime within the 24-hr period. For lettuce there were three replicate, 35 d crop cycles and for tomatoes plants received 15 weeks of treatment after reaching the fruiting stage with no replication. Both algorithms controlled DLI close to target. For lettuce, LASSI with HPS led to larger plant height and volume and increased fresh weight (but not dry weight) vs. RT LASSI with LED. For tomatoes, RT-LASSI with LED led to about a 30% greater tomato yield vs. LASSI with HPS. Increased yield was associated with increased fruit size but not increased fruit or truss number. Brix of HPS grown fruit was higher than LED fruit. While air temperature was very similar between both treatments, HPS fixtures may have increased plant temperature of LED. More research is needed to determine if plant impacts were due to type of lighting fixture and associated plant temperature and light spectrum or to the control algorithm itself (spreading supplemental lighting across greater hours per day).
The surging demand for sustainable agriculture has accelerated the adoption of indoor vertical farming as a pragmatic solution. Lettuce, a cornerstone crop in this context, assumes significant importance. Accurate forecasting of lettuce yield is indispensable for optimizing resource allocation and ensuring a steady supply. Most existing models used either environmental data or images to predict yield predictions, which could be erroneous for complex systems. This study aims to improve the accuracy of yield prediction in indoor farming settings with a hybrid model. First, we applied the feedforward neural network and random forest models for yield prediction, leveraging data from environmental sensors, cultivation practices, and historical yield records. Then, a convolutional neural network model is tailored to forecast yield using image data captured by RGBD cameras. Based on our results, we found reasonable accuracy in terms of RMSE and MAE, which range between 10-25 gm and 28-49 g, respectively. By amalgamating these diverse models, we aim to elevate yield prediction accuracy. It’s hypothesized that the proposed hybrid model would outperform individual approaches, offering invaluable insights for indoor vertical farming operations decision-making.
Maintaining a target pH range is important for root zone management and overall plant growth and quality. Commercial soilless substrates often contain liming amendments to increase initial substrate pH to between 5.5 and 6.2. Hydroponic nutrient solutions are less-well buffered than soilless substrates and can experience pH drift in the absence of frequent monitoring and adjustment. Hydroponic deep water culture (DWC) was explored for strawberry (Fragaria × ananassa) research studies, to more-easily collect root growth parameters and root samples for elemental analysis, compared to soilless substrate culture. However, an effective strategy for pH management needed to be developed. The objective of this study was to develop a protocol for growing strawberry mother plants hydroponically. First, three hydroponic systems (drip-irrigated coarse perlite, drip-irrigated sand, and DWC) were compared to a peat-based soilless substrate control. Plants received a modified strawberry nutrient solution (Yamazaki) at a nitrogen (N) concentration of 100 mg·L-1. Plants grew similarly across the four growing systems. Deep water culture provided the easiest access to clean roots; however, root zone pH decreased
Dissolved oxygen (DO) level in hydroponic solution is an important factor affecting plant root development and water and nutrient uptake. However, precisely controlling the DO level in hydroponics has always been difficult due to the direct linkage of solution temperature and oxygen concentrations, especially under different aeration methods. Besides potentially controlling solution temperature, using liquid oxygen fertilization such as hydrogen peroxide (H2O2) has been shown to burst increase DO concentration in the solution, and ozonation, which is a sanitization treatment, has the potential to adjust DO level by supplying oxygen in nutrient solution. Our objective was to evaluate the effects of different DO levels and oxygenation strategies in a hydroponic system for the optimal growth of kale (Brassica oleracea) and arugula (Eruca vesicaria). In this study, we used ozone generators and hydrogen peroxide (H2O2) as a DO enrichment method in addition to the air pump-based aeration system to test the effects of different DO levels – low, medium, high as 6, 9, 12 mg/L, respectively – on kale ‘KX-1’ and ‘Red Russian’, and arugula ‘Astro’ and ‘Esmee’ grown in a deep water culture system. Treatment without using ozone generators or H2O2 was assigned as control. The study was arranged as a completely randomized design with three replications. DO and temperature probes were connected to a datalogger to trigger ozone generators and H2O2 injection using a relay once the DO levels were below the set thresholds. Weekly measurements were taken for plant height, leaf and anthocyanin chlorophyll content. The final harvest additionally measured leaf area, shoot and root biomass the leaf soluble solids content, titratable acidity, and leaf nutrient concentration. Plants grown under a high DO level had a higher root-to-shoot ratio, but the overall higher plant yield was achieved under the medium DO level. This system demonstrated that precise DO level control could be achieved using a sensor-based system.
In the evolving landscape of controlled environment agriculture (CEA), precise temperature management remains a pivotal factor in enhancing the growth, development, productivity, and quality of high-value leafy greens. Our research identifies the cardinal temperatures — base (Tb), optimum (Topt), and maximum (Tmax) — for red-leaf and green butterhead lettuce (Lactuca sativa), arugula (Eruca sativa), and kale (Brassica oleracea), comparing how both constant mean daily temperature (MDT) within a greenhouse and positive day-night temperature differences (DIF) in a growth chamber influence plant growth and development. In the greenhouse, we had a constant MDT of 8, 13, 18, 23, 28, and 33 °C under a photosynthetic photon flux density (PPFD) of 220 µmol∙m‒2∙s‒1 for 12 h∙d–1, while in the growth chamber we targeted the same MDTs with air day/night (12 h/12 h) set points of 11/5 °C, 16/10 °C, 21/15 °C, 26/20 °C, 31/25 °C, or 36/30 °C under a PPFD of 300 µmol∙m‒2∙s‒1. Both arugula and kale had greater biomass accumulation at lower Tb and Topt compared to lettuce, suggesting a propensity for growth under a cooler MDT. Specifically, the Topt for fresh mass accumulation was found to be at 24.7 °C for arugula, 22.9 °C for kale, and higher for lettuce cultivars 'Rex' and 'Rouxaï RZ' at 24.7 and 26.2 °C, respectively. We found that DIF exerted minimal influence on these crops, emphasizing the critical role of MDT in influencing their developmental outcomes. Additionally, our research provides insight into the impact of temperature on various physiological and morphological parameters, such as leaf unfolding rate, biomass accumulation, and susceptibility to physiological disorders such as bolting or tipburn. This study underscores the importance of precise temperature management in CEA, offering guidance for producers seeking to optimize energy use while maximizing crop yield and quality.
Light Intensity Regulates the Interactive Effects between Far-red light and Temperature on Lettuce Growth, Morphology, Photosynthesis, and Secondary Metabolite - Sangjun Jeong Lighting Around the Clock: Greenhouse Production with 24h Lighting - Jason Lanoue Explore a Cost-friendly Way for Plant Nitrogen Stress Identification - Ping Yu Optimization of Irrigation Based on Substrate Type for Tomato Production in the Dutch Bucket Hydroponic System - Milon Chowdhury The Secondary Metabolite Production and Growth Responses of Cannabis to Thigmomorphogenesis in a Controlled Environment - Jose Franco Da Cunha Leme Filho Simulated Climate-change-related Environmental Stressors Can Alter the Yield and Metabolomics of Tomato - Marlo Vandiver
Phytochromes (PHYs) play a dual role in sensing light spectral quality and temperature. PHYs can interconvert between their active and inactive forms upon absorption of red and far-red light (Photoconversion). In addition, the active form can be converted to the inactive form in a temperature-dependent manner (Thermal Reversion). Our recent research found that while far-red (FR; 700-800 nm) light promoted leaf expansion and biomass of lettuce (Lactuca sativa) ‘Rex’ under cooler temperatures (20-24 °C), it reduced plant biomass and leaf area under warm temperature (28 °C). Considering that PHY activity would be driven mainly by photoconversion, not thermal reversion, under higher light intensity (HL), we hypothesized that the magnitude of the interaction between FR light and temperature on plant growth and morphology decreases with increasing light intensity. Lettuce ‘Rex’ was grown under three temperature regimes (20, 24, and 28 oC) x two spectral treatments [0 and 20% of FR light in total photon flux density (TPFD; 400-800 nm)] x two light intensities [150 (lower light intensity; LL) and 300 (HL) μmol·m-2·s- 1 of TPFD]. Our results showed that the effects of FR light on leaf expansion and stem elongation depended on temperature under LL. Specifically, FR light significantly promotes leaf expansion under cooler temperatures (20 oC), while decreasing total leaf area under warmer temperatures (24 and 28 oC). However, the magnitude of the interactive effects between FR light and temperature on plant morphology decreased under HL, leading to a consistent increase in total leaf area by FR light under HL. Similarly, FR light promoted plant growth under HL regardless of temperature, while reducing plant biomass under warm temperature under LL. Crop yield was primarily dependent on photon capture rather than photosynthetic efficiency per unit leaf area. FR light generally decreased the production of secondary metabolites (e.g., phenolics and flavonoids), while warm temperature and HL treatments increased the production of secondary metabolites. We concluded that the interactive effects between FR light and temperature on plant growth and morphology are further dependent on light intensity. The combination of FR light, warm temperature, and HL could maximize crop yield without reducing nutritional quality in terms of antioxidant capacity.
Photoperiod extension in controlled environment agriculture - including the use of 24h continuous light - can be used to reduce light fixture and electricity costs in regions with lower night electricity rates. However, many plant species develop photoperiodic injury characterized by leaf chlorosis and yield reduction at a critical species-specific photoperiod threshold. Here we will discuss the response of different plant species to continuous lighting strategies. We will first challenge the conventional notion that dark adapted chlorophyll fluorescence (Fv/Fm) measurements are the most appropriate when assessing photoperiodic injury. We provide evidence that light adapted (φPSII) measurements allow for a more in-depth understanding of the light capture process at photosystem II. Through RNA-sequencing in tomato, we determined that the use of a dynamic 24h lighting treatment (i.e., red light during the day and blue light during the night) lead to normal gene expression of chlorophyll a/b binding (CAB) proteins. However when tomato plants were grown under a static continuous lighting strategy (i.e., red blue lighting for 24h) at the same daily light integral, gene expression of CAB proteins were drastically reduced, resulting in chlorosis and yield reduction. In comparison to tomatoes, cucumbers tend to be more tolerant to long photoperiods and therefore continuous lighting can have an immediate impact in commercial production. Initial results in cucumbers show that a continuous lighting strategy can decrease the lighting electricity costs by 26% and greenhouse gas emissions by 38.9% per unit of produce compared to a 16h control treatment. Using the knowledge gained throughout our studies, we propose a lighting strategy which gamifies the electricity market to further reduce costs and greenhouse gas emissions.
Plant stress can cause economic loss for plant production and is hard and expensive to identify at times. Thus, a greenhouse experiment was conducted to find an easy and cost-friendly way to identify plant stress, set up thresholds and values for the initiation of plant nitrogen stresses. Four different crops (basil, pepper, marigold, and sage) were included and treated with five different nitrogen levels (0%, 25%, 50%, 75%, and 100%). Plant height, width and leave greenless (indicated by SPAD) were measured weekly. Pictures were taken weekly. Software Image J was used to process pictures and R was used for data analysis. We found that plants with higher nitrogen treatments (75%-100%) all grow better and have higher SPAD than other treatments, except for bail. Also, RGB value could indicate plant nitrogen status with high accuracy. Plants become nitrogen stressed when SPAD falls to 25. Red and green values in RGB have negative correlations directly with SPAD and indirectly with nitrogen stress status. When the R and G values are higher than 150 and 185, respectively, we can safely predict that the plant is nitrogen stressed. In conclusion, using RBG value can be a cost-friendly way for plant stress identification.
Dutch bucket hydroponic systems are used for high-wire crop production such as tomatoes, cucumbers, or peppers, and are typically filled with perlite as a substrate. Through past research, our group identified pine bark and wood fiber as sustainable alternative substrates for high-wire tomato production. Typically, greenhouse tomato growers utilize leachate-based or timed irrigation; however, the use of a water content sensor could precisely identify the irrigation set-point for different substrates, potentially saving water and fertilizers. This study aimed to optimize the irrigation rate for greenhouse tomato ('Favorita F1') production in the Dutch bucket hydroponic system using a soil water content sensor. Three types of substrates (perlite, pine bark, and wood fiber-coir mix (60:40)) and four different gravimetric water contents (100%, 120%, 140%, and 160%) were considered. The experiment was conducted with three replications in a completely randomized design, with the irrigation treatments under the perlite substrate serving as the control. Physical parameters, such as the number of leaves and plant height, were significantly higher in the wood fiber-coir mix and pine bark at 160% irrigation, and lowest under perlite at 100% water content. However, there was no significant difference among the treatments for the number of flower (fruit) clusters. The plant leaf area measurements indicated better vegetative growth with wood fiber-coir mix at 160% water content, whereas pine bark at 160% water content resulted in a higher yield and better fruit quality. In contrast, phytochemicals such as Brix, vitamin C, titratable acidity, lycopene, beta-carotene, and phenolic compounds were significantly higher in the organic substrates (pine bark and wood fiber) with low water content (100% to 120%) and lower in perlite with high water content (140% to 160%). The highest and lowest concentrations of phytochemicals varied between 13% to 67%. There was no significant difference among the treatments (substrates and water contents) in terms of tissue mineral analysis. In general, plants grown in wood fiber-coir mix treatments required 28% and 51% less irrigation compared to those in pine bark and perlite treatments, respectively. Plants grown in organic substrates require less water, and the yield quantity and quality are either similar to or higher than those in perlite. Out of the organic substrates, wood fiber-coir mix can be used in Dutch bucket systems to conserve water and nutrients, enhancing yield quantity and quality, and thereby achieving environmental sustainability.
As legalization continues to change the cannabis industry, we see an influx of creative innovation, funding, and research as more entities enter the field. The two innovative growing management investigated in this study were Mechanical Vibration Training (MVT) and High Stress Training (HST). MVT was carried out using a grid exposing the plants to 200 Hz vibration, and HST is a practice that involves damaging the vascular bundles, pith, and cortex of the main stem while leaving the epidermis intact. MVT is a newer technique still in development, as Thigmo-priming has been shown to change plant morphology and chemistry and even increase the speed and magnitude of future stress responses. Many industry leaders claim that the advantages of using HST include higher canopy, increased biomass and cannabinoid concentrations, and more effective IPM strategies. However, studies validating these claims are still being determined. This study aims to compare each growing management under the overall category of Thigmomorphogenesis or mechanostimulation against control (no artificial mechanical stimulation) and tease out any synergism between the treatments. We hypothesize that applying mechanostimulation to cannabis plants will enhance their growth and increase secondary metabolite production. The environment-controlled growth units housed the treatments consisted of 1-Control, 2-MVT, 3-HST, and 4-MVT HST. Each growth unit contained five-gallon fabric pots with a single Suver Haze plant. An amended coco coir substrate was used with a water-soluble nutrient solution, and optimal growing conditions, including lighting, were maintained equally in all environment-controlled growth units. Weekly plant parameters included stem diameter, plant height, NDVI, chlorophyll concentration, and photosynthetic efficiency. After-harvest parameters included above/below ground biomass, yield mass, bucked biomass, trichome density, and cannabinoid levels. Morphological and numerical differences between treatments indicated the potential for a shorter, more efficient growth cycle with higher cannabinoid levels. Further testing is currently underway.
The Cannabis Biology and Cultivation Systems lab focuses on areas of controlled environment agriculture, plant stress, secondary metabolites, nutraceutical/pharmaceutical biology, and growing practices. The research team aims to determine how to leverage environmental controls (light... Read More →
Climate change challenges all aspects of food production, including standard greenhouse products, such as tomatoes. The cause of climate change can be directly attributed to the rise in carbon dioxide (CO2) levels, leading to increased temperatures and drought severity. Tomatoes are the most produced fruit crop globally, and in addition to their economic benefits contain several vitamins and minerals essential for human health. The objective of this study was to assess the multi-variable effects of simulated climate change on tomato plants by investigating the combination of elevated CO2 (800 ppm vs 400 ppm), increased temperature (28℃ vs 21℃), and water deficit stress (20% decrease from control) across three development stages: juvenile, anthesis, and fully mature tomato. ‘Sweet ‘N’ Neat Scarlet’ tomatoes (Solanum lycopersicum) were grown in four plant growth chambers in a 2 x 2 x 2 factorial design with four replications. Quality parameters included photosynthetic efficiency, growth index, dry weight, flower number, fruit number, and fruit size. Inductively coupled plasma mass spectrometry (ICP-MS) and oxygen radical absorbance capacity (ORAC) analyses were measured at each of the three stages when applicable. Preliminary data suggests that higher temperatures and CO2 increase (p
