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Consumption of fruit and vegetable crops rich in lutein and β-carotene carotenoids is associated with reduced risk of cancers and aging eye diseases. Kale (Brassica oleracea L. var. acephala D.C.) ranks highest for lutein concentrations and is an excellent source of dietary carotenoids. Kale plants were grown under varied photoperiods to determine changes in the accumulation of fresh and dry biomass, chlorophyll a and b, and lutein and β-carotene carotenoids. The plants were cultured in a controlled environment using nutrient solutions under photoperiod treatments of 6, 12, 16, or 24 hours (continuous). Fresh and dry mass production increased linearly as photoperiod increased, reaching a maximum under the 24-hour photoperiod. Maximum accumulation of lutein, β-carotene, and chlorophyll b occurred under the 24-h photoperiod at 13.5, 10.4, and 58.6 mg/100 g fresh mass, respectively. However, maximum chlorophyll a (235.1 mg/100 g fresh mass) occurred under the 12-hour photoperiod. When β-carotene and lutein were measured on a dry mass basis, the maximum accumulation was shifted to the 16-hour photoperiod. An increase in photoperiod resulted in increased pigment accumulation, but maximum concentrations of pigments were not correlated with maximum biomass production.

Two experiments were completed to determine whether the form and concentration of iron (Fe) affected Fe toxicity in the Fe-efficient species Pelargonium ×hortorum `Ringo Deep Scarlet' L.H. Bail. grown at a horticulturally low substrate pH of 4.1 to 4.9 or Fe deficiency in the Fe-inefficient species Calibrachoa ×hybrida `Trailing White' Cerv. grown at a horticulturally high substrate pH of 6.3 to 6.9. Ferric ethylenediaminedi(o-hydroxyphenylacetic) acid (Fe-EDDHA), ferric ethylenediamine tetraacetic acid (Fe-EDTA), and ferrous sulfate heptahydrate (FeSO₄·7H₂O) were applied at 0.0, 0.5, 1.0, 2.0, or 4.0 mg ·L^–1 Fe in the nutrient solution. Pelargonium showed micronutrient toxicity symptoms with all treatments, including the zero Fe control. Contaminant sources of Fe and Mn were found in the peat/perlite medium, fungicide, and lime, which probably contributed to widespread toxicity in Pelargonium. Calibrachoa receiving 0 mg Fe/L exhibited severe Fe deficiency symptoms. Calibrachoa grown with Fe-EDDHA resulted in vigorous growth and dark green foliage, with no difference from 1 to 4 mg·L^–1 Fe. Using Fe-EDTA, 4 mg Fe/L was required for acceptable growth of Calibrachoa, and all plants grown with FeSO₄ were stunted and chlorotic. Use of Fe-EDDHA in water-soluble fertilizer may increase the upper acceptable limit for media pH in Fe-inefficient species. However, iron and Mn present as contaminants in peat, irrigation water, or other sources can be highly soluble at low pH. Therefore, it is important to maintain a pH above 6 for Fe-efficient species regardless of applied Fe form or concentration, in order to avoid the potential for micronutrient toxicity.

Heat-tolerant bluegrass varieties were developed to resist dormancy and retain pigmentation during heat stress events. The objective of this study was to investigate the influence of grass species, nitrogen (N) fertilization, and seasonality on the accumulation patterns of lutein, β-carotene, and chlorophyll a and b in the leaf tissues of turfgrass. The heat-tolerant bluegrass cultivars Dura Blue and Thermal Blue (Poa pratensis L. × Poa arachnifera Torr.), Apollo kentucky bluegrass (Poa pratensis L.), and Kentucky 31 tall fescue (Festuca arundinacea Schreb.) were compared for the accumulation of plant pigments. Evaluations were conducted over 2 consecutive years (Years 4 and 5 after establishment) during two different seasons (spring and summer) and under varying N fertilization. Fertilizer applications of 5, 14, and 27 g N/m²/year resulted in a significant positive correlation for the accumulation of leaf blade lutein and chlorophyll a and b, but not for β-carotene. The accumulation of the four measured plant pigments among the grasses was significantly different with ‘Apollo’ having the largest concentration of pigments followed by ‘Dura Blue’, ‘Thermal Blue’, and finally ‘Kentucky 31’. Specifically, when comparing the cultivars Apollo and Kentucky 31, the pigment levels decreased 27%, 26%, 26%, and 23% for lutein, β-carotene, and chlorophyll a and b, respectively. The interesting observation of the analysis of the grass pigment concentrations was that the least reported heat-tolerant cultivar in our study (‘Apollo’) had the largest measured pigment concentrations.

Plant spacing and production systems are important factors for maximizing production of greenhouse-grown tomatoes (Solanum lycopersicum). Two studies were conducted simultaneously and independently, each in a 33 × 96-ft greenhouse in Fall 2008 and Spring 2009 using perlite soilless bag culture. The purpose of the first study was to evaluate yield and fruit weight of ‘Trust’ tomatoes spaced 12, 16, 20, 24, or 28 inches in-row. The second study was conducted to determine the effect of pruning production systems on yield and fruit weight. The first system is pruning two plants per bag each to a single leader and the second is pruning one plant per bag to double leader. A plant spacing of 28 inches resulted in significantly more fruit per plant than the 12-inch plant spacing. However, yield per area decreased with wider plant spacings. Plants spaced 12 inches apart in-row produced 2.8 and 3.8 lb/ft² total yield in the fall and spring, respectively, compared with plants spaced 28 inches apart that produced 1.7 and 2.2 lb/ft² in the fall and spring. Using a production system with one plant per bag pruned to a double leader increased yield by 6.4 lb/plant in the fall and 15.7 lb/plant in the spring. On a per bag basis, pruning two tomato plants to one leader increased total yield by 2.6 lb/bag and was more economical in the fall; whereas, in the spring, the double leader production system did not affect yield but was more economical.

Glucosinolates (GSs) and carotenoids are important plant secondary metabolites present in several plant species, including arabidopsis (Arabidopsis thaliana). Although genotypic and environmental regulation of GSs and carotenoid compounds has been reported, few studies present data on their regulation at the molecular level. Therefore, the objective of this study was to explore differential expression of genes associated with GSs and carotenoids in arabidopsis in response to selenium fertilization, shown previously to impact accumulations of both classes of metabolites in Brassica species. Arabidopsis was grown under 0.0 or 10.0 μM Na₂SeO₄ in hydroponic culture. Shoot and root tissue samples were collected before anthesis to measure GSs and carotenoid compounds and conduct gene expression analysis. Gene expression was determined using arabidopsis oligonucleotide chips containing more than 31,000 genes. There were 1274 differentially expressed genes in response to selenium (Se), of which 516 genes were upregulated. Ontology analysis partitioned differentially expressed genes into 20 classes. Biosynthesis pathway analysis using AraCyc revealed that four GSs, one carotenoid, and one chlorophyll biosynthesis pathways were invoked by the differentially expressed genes. Involvement of the same gene in more than one biosynthesis pathway indicated that the same enzyme may be involved in multiple GS biosynthesis pathways. The decrease in carotenoid biosynthesis under Se treatment occurred through the downregulation of phytoene synthase at the beginning of the carotenoid biosynthesis pathway. These findings may be useful to modify the GS and carotenoid levels in arabidopsis and may lead to modification in agriculturally important plant species.

Previous research in our group demonstrated that short-duration exposure to narrow-band blue wavelengths of light can improve the nutritional quality of sprouting broccoli (Brassica oleacea var. italica) microgreens. The objective of this study was to measure the impact of different percentages of blue light on the concentrations of nutritional quality parameters of sprouting broccoli microgreens and to compare incandescent/fluorescent light with light-emitting diodes (LEDs). Microgreen seeds were cultured hydroponically on growing pads under light treatments of: 1) fluorescent/incandescent light; 2) 5% blue (442 to 452 nm)/95% red (622 to 632 nm); 3) 5% blue/85% red/10% green (525 to 535 nm); 4) 20% blue/80% red; and 5) 20% blue/70% red/10% green in controlled environments. Microgreens were grown at an air temperature of 24 °C and a 16-hour photoperiod using a light intensity of 250 μmol·m⁻²·s⁻¹ for all light treatments. On emergence of the first true leaf, a nutrient solution of 42 mg·L⁻¹ nitrogen (N) (20% Hoagland’s #2 solution) was used to submerge the growing pads. Microgreens were harvested after 20 days under the light treatments and shoot tissues were processed and measured for nutritionally important shoot pigments, glucosinolates, and mineral nutrients. Microgreens under the fluorescent/incandescent light treatment had significantly lower shoot fresh mass than plants under the 5% blue/95% red, 5% blue/85% red/10% green, and the 20% blue/80% red LED light treatments. The highest concentrations of shoot tissue chlorophyll, β-carotene, lutein, total carotenoids, calcium (Ca), magnesium (Mg), phosphorus (P), sulfur (S), boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), glucoiberin, glucoraphanin, 4-methoxyglucobrassicin, and neoglucobrassicin were found in microgreens grown under the 20% blue/80% red light treatment. In general, the fluorescent/incandescent light treatment resulted in significantly lower concentrations of most metabolites measured in the sprouting broccoli tissue. Results from the current study clearly support data from many previous reports that describe stimulation of primary and secondary metabolite biosynthesis by exposure to blue light wavelengths from LEDs.

Multilayer vertical production systems using sole-source (SS) light-emitting diodes (LEDs) can be an alternative to more traditional methods of microgreens production. One significant benefit of using LEDs is the ability to select light qualities that have beneficial impacts on plant morphology and the synthesis of health-promoting phytochemicals. Therefore, the objective of this study was to quantify the impacts of SS LEDs of different light qualities and intensities on the phytochemical content of brassica (Brassica sp.) microgreens. Specifically, phytochemical measurements included 1) total anthocyanins, 2) total and individual carotenoids, 3) total and individual chlorophylls, and 4) total phenolics. Kohlrabi (Brassica oleracea var. gongylodes), mustard (Brassica juncea ‘Garnet Giant’), and mizuna (Brassica rapa var. japonica) were grown in hydroponic tray systems placed on multilayer shelves in a walk-in growth chamber. A daily light integral (DLI) of 6, 12, or 18 mol·m⁻²·d⁻¹ was achieved from SS LED arrays with light ratios (percent) of red:blue 87:13 (R₈₇:B₁₃), red:far-red:blue 84:7:9 (R₈₄:FR₇:B₉), or red:green:blue 74:18:8 (R₇₄:G₁₈:B₈) with a total photon flux from 400 to 800 nm of 105, 210, or 315 µmol·m⁻²·s^–1 for 16 hours, respectively. Phytochemical measurements were collected using spectrophotometry and high-performance liquid chromatography (HPLC). Regardless of light quality, total carotenoids were significantly lower under increasing light intensities for mizuna and mustard microgreens. In addition, light quality affected total integrated chlorophyll with higher values observed under the light ratio of R₈₇:B₁₃ compared with R₈₄:FR₇:B₉ and R₇₄:G₁₈:B₈ for kohlrabi and mustard microgreens, respectively. For kohlrabi, with increasing light intensities, the total concentration of anthocyanins was greater compared with those grown under lower light intensities. In addition, for kohlrabi, the light ratios of R₈₇:B₁₃ or R₈₄:FR₇:B₉ produced significantly higher anthocyanin concentrations compared with the light ratio of R₇₄:G₁₈:B₈ under a light intensity of 315 µmol·m⁻²·s⁻¹. Light quality also influenced the total phenolic concentration of kohlrabi microgreens, with significantly greater levels for the light ratio of R₈₄:FR₇:B₉ compared with R₇₄:G₁₈:B₈ under a light intensity of 105 µmol·m⁻²·s⁻¹. However, the impact of light intensity on total phenolic concentration of kohlrabi was not significant. The results from this study provide further insight into the selection of light qualities and intensities using SS LEDs to achieve preferred phytochemical content of brassica microgreens.

Lettuce (Lactuca sativa L.) is one of the most consumed fresh vegetables in the United States. However, lettuce production is heavily limited to California and Arizona, posing a high risk to the supply chain. Hydroponic production is a soilless cultivation method and provides a sustainable alternative to growing lettuce in the field. Light is a critical factor in plant development, and light quality highly affects plant morphogenesis. The goals of this study were 2-fold, with the first to investigate the growth of 26 lettuce cultivars under a hydroponic system supplemented with fluorescent light to determine adaptability. Subsequently, the second goal was to determine how light-emitting diodes (LEDs) affect lettuce plant morphology and photosynthesis compared with fluorescent light for four lettuce cultivars. Results showed that 23 of 26 lettuce cultivars were grown successfully using a hydroponic system. However, lettuce grown under fluorescent light experienced stem elongation—a morphological response to low-light conditions known as shade avoidance syndrome. Stem elongation decreased significantly under LED light, whereas other morphological characteristics remained relatively the same between the two light treatments. Although there were no differences in dry weight and leaf area, the carbon assimilation rate increased significantly in lettuce cultivars Coastal Star, Muir, Green Butter, and Rouge d’Hiver when treated with LED light. Correspondingly, intercellular carbon dioxide (CO₂) decreased in these four lettuce cultivars under the LED light treatment. Our study results indicate that LED light increased photosynthetic activity and reduced stem elongation to enhanced lettuce quality.

Production of high-quality nursery liners has long been a foundation principle for enabling success and business longevity in the competitive nursery industry. Unfortunately, many different characteristics can be used to define liner “quality,” ranging from physiological parameters measurable in scientific studies field establishment success and transplant production performance to gut-level hunches on the part of growers. A more complete understanding of what buyers are looking for in a bare-root liner would significantly enhance the success of producers in meeting the demands of end-users. As a result, a choice study involving a point-of-purchase simulation was designed to assess preferences of green industry professionals when viewing bare-root 1 + 0 nursery liners. A conjoint design was used for this study and involved six key attributes of liners: 1) number of first-order lateral roots (FOLR); 2) price; 3) production region; and uniformities of 4) height; 5) canopy density; and 6) liner caliper. A visual survey based on a large, color graphic depicting six distinct bare-root 1 + 0 liners with different combinations of attributes was administered together with a demographic questionnaire at four different green industry tradeshows and extension grower education and outreach venues in the southeastern United States. Results from 248 completed surveys corroborated previously reported results suggesting that high FOLR is the most important attribute influencing preference for 1 + 0 liner products followed by uniform liner height and canopy density. Contrary to a priori expectations, neither price nor region of production substantially influenced product preference. Utility values were calculated for each attribute level using outputs from the experimental model. These values can be used by growers to adjust production methods to improve liners with attributes that end-users value most. In addition, growers will be able to better estimate product ratings, redirect marketing efforts, and assess sales potential for various bare-root 1 + 0 liner products in U.S. markets.

In the present study, carotenoid concentrations and profiles of carotenoids were determined at harvest and during storage in fruit of several cultigens of winter squash, including several New Hampshire (NH) breeding lines, the cultivars Waltham Butternut and Puritan Butternut in Cucurbita moschata (Duch.), and the hybrid cultivars Sunshine, Eclipse, Space Station, and Thunder in Cucurbita maxima (Duch.). Cultigens were grown at research farms in either Madbury or Durham, NH, in 2007, 2008, and 2009, and fruit were harvested at either 40 or 60 days after pollination (DAP), and stored for 0, 30, or 60 days at 14 °C before sampling. Total carotenoid concentrations were determined spectrophotometrically and carotenoid profiles were determined using high-performance liquid chromatography (HPLC). Carotenoid concentrations in fruit samples of C. maxima cultigens harvested at 60 DAP ranged from 146 to 320 μg·g⁻¹ fresh weight (FW), compared with concentrations of 274 to 623 μg·g⁻¹ FW after storage for 60 days. Carotenoid concentrations were lower among C. moschata cultigens, ranging from 42 to 145 μg·g⁻¹ FW at 60 DAP, and from 84 to 239 μg·g⁻¹ FW after 60-day storage. The nutritionally important carotenoids, lutein, zeaxanthin, and β-carotene, comprised 41% to 63% of the total carotenoid profile in the C. maxima kabocha hybrids; whereas, the carotenoids neoxanthin and flavoxanthin comprised 37% to 59%. β-Carotene and lutein were the major nutritionally beneficial carotenoids identified in ‘Waltham Butternut’ and three inbred lines of C. moschata, along with much smaller concentrations of α-carotene. Neoxanthin and violaxanthin comprised between 14% and 29% of the total carotenoid profiles among the four cultigens analyzed. In the popular cultivar Waltham Butternut, the β-carotene concentration was 17.3 μg·g⁻¹ FW at 60 DAP, but increased to a maximum of 57.8 μg·g⁻¹ FW after storage for 30 days; whereas, lutein concentrations increased from 27.3 μg·g⁻¹ FW at 60 DAP to 44.6 μg·g⁻¹ FW after 60-day storage. In Sunshine, a popular kabocha cultivar, β-carotene increased from 26.0 μg·g⁻¹ FW at 60 DAP to 104 μg·g⁻¹ FW after 60-day storage. Lutein + zeaxanthin concentrations in ‘Sunshine’ were 58.8 μg·g⁻¹ FW at 60 DAP, but increased only to 71.8 μg·g⁻¹ FW after 60-day storage. Total carotenoid concentrations and carotenoid profiles in ‘Sunshine’ over three growing seasons, and in ‘Waltham Butternut’, ‘NH.Mo421’, and ‘NH.Mo851’ over two growing seasons, were similar.