The use of light-emitting diodes (LEDs) for plant production is a new field of research that has great promise to optimize wavelength-specific lighting systems for precise management of plant physiological responses and important secondary metabolite production. In our experiment, hydroponically cultured kale plants (Brassica oleracea L. var. acephala D.C.) were grown under specific LED wavelength treatments of 730, 640, 525, 440, and 400 nm to determine changes in the accumulation of chlorophylls, carotenoids, and glucosinolates. Maximum accumulation, on a fresh mass basis, of chlorophyll a and b and lutein occurred at the wavelength of 640 nm, whereas β-carotene accumulation peaked under the 440-nm treatment. However, when lutein was measured on a dry mass basis, maximum accumulation was shifted to 440 nm. Sinigrin was the only glucosinolate to respond to wavelength treatments. Wavelength control using LED technology can affect the production of secondary metabolites such as carotenoids and glucosinolates with irradiance levels also a factor in kale. Management of irradiance and wavelength may hold promise to maximize nutritional potential of vegetable crops grown in controlled environments.
Mark G. Lefsrud, Dean A. Kopsell, and Carl E. Sams
John M. Kauffman, John C. Sorochan, and Dean A. Kopsell
Thatch-mat and organic matter (OM) accumulation near the putting green soil surface impacts soil physical properties and turf performance. Excessive thatch and OM can encumber infiltration of water and oxygen into the soil profile and slow drainage of excess water away from the putting surface. Proper sampling of thatch-mat depths and OM contents is vital for management of putting green turf; therefore, a study was performed in Knoxville, TN, to derive proper sampling procedures of these important parameters using ‘TifEagle’ and ‘Champion’ bermudagrass (Cynodon dactylon × C. transvaalensis), ‘SeaDwarf’ seashore paspalum (Paspalum vaginatum), and ‘Diamond’ zoysiagrass (Zoysia matrella). ‘TifEagle’ and ‘Champion’ accumulated thatch-mat to a greater depth than ‘SeaDwarf’ and ‘Diamond’. However, ‘SeaDwarf’ had a higher OM content than ‘Diamond’ and both had higher OM contents than ‘TifEagle’ and ‘Champion’. Data generated from sampling procedures indicate that previous studies often undersampled plots for thatch-mat depth; however, previous sampling procedures have not traditionally undersampled plots for OM. Data in this study provide a range of confidence and minimum detectable difference levels which may allow future researchers to more accurately sample ‘TifEagle’, ‘Champion’, ‘SeaDwarf’, and ‘Diamond’ putting green plots for thatch-mat depth and OM content.
T. Casey Barickman, Dean A. Kopsell, and Carl E. Sams
Plants encounter various environmental stress factors that can potentially impact nutritional requirements and fruit quality. Adequate levels of calcium (Ca) in tomato (Solanum lycopersicum) fruit have positive effects on fruit quality, specifically firmness. One of the results of insufficient Ca uptake and movement in tomato is the physiological disorder blossom-end rot (BER), which is associated with a Ca deficiency in the distal fruit tissue. Previous research has demonstrated that foliar abscisic acid (ABA) applications decreased the incidence of BER and increased the uptake of Ca into fruit tissue. This study examined how root and foliar spray ABA applications, individually and in combination, affect the partitioning of Ca between the leaves and fruit of tomato plants, especially in the distal tissue, and how ABA affects the incidence of BER in the distal tissue of tomato fruit. ‘Mt. Fresh Plus’ tomato were grown in the greenhouse at 25/20 °C (day/night) under a 16-hour photoperiod. Plants were treated with different Ca concentrations in the fertilizer solution. Plants were also treated with foliar spray ABA applications weekly. Calcium was applied through the irrigation lines at 60, 90, or 180 mg·L−1. ABA treatments were applied as a combination of foliar sprays and root applications. Foliar ABA applications, treatments consisted of deionized (DI) water control (0.0 mg ABA/L) or 500 mg ABA/L. For ABA root applications, treatments consisted of a DI water control (0.0 mg ABA/L) or 50 mg ABA/L applied through the irrigation lines. ABA spray treatments were applied once weekly until dripping from the foliage (tops of pots were covered to prevent spray drip into the pot), whereas root applications were applied four times per day through the irrigation system. Fruit tissues were harvested 84 to 90 days after seeding. Fruit tissue was harvested at red ripe maturity and evaluated for yield, BER, and Ca concentrations. Leaves were harvested at the time of fruit and were analyzed for Ca concentrations. The results indicate that a combination of the spray and root applications of ABA resulted in the greatest decrease in BER. The foliar spray application of ABA combined with the Ca treatment of 180 mg·L−1 decreased the incidence of BER. Results also demonstrate that ABA treatments are effective in increasing fruit Ca and preventing BER in the early stages of plant development but are less effective in preventing Ca deficiency in the later stages of growth.
Dilip R. Panthee, Dean A. Kopsell, and Carl E. Sams
Glucosinolates (GS) are important secondary plant metabolites present in several plant species, including Arabidopsis thaliana (L.) Heynh. Although genotypic differences among a limited number of samples from a limited geographical range have been reported, there have been few studies exploring the variation from a wider genetic base. The objective of this study was to explore the genetic variation for GS in A. thaliana collected throughout the world. We screened 58 A. thaliana ecotypes collected from the geographic area of lat. 15° N to lat. 59° N and long. 137° E to long. 123° W. Elevation in these areas ranged from sea level to over 480 m. We believe that this study has covered a large geographical region and captured most of the available genetic variation in A. thaliana for GS. There was no geographical trend in A. thaliana shoot or seed tissue for GS concentration. Total shoot GS ranged from 1.1 to 52.8 μmol·g−1 dry weight (DW), averaging 9.3 μmol·g−1 DW among all ecotypes. Total seed GS ranged from 1.6 to 41.8 μmol·g−1 DW with an average of 16.8 μmol·g−1 DW among all ecotypes. Low and high GS-accumulating A. thaliana ecotypes identified in this study may provide a basis for further genetic analysis for GS metabolism. Information provided may also prove useful for improving concentrations of nutritionally beneficial GS in vegetable Brassicas.
T. Casey Barickman, Dean A. Kopsell, and Carl E. Sams
One important regulator that coordinates response to environmental stress is the hormone abscisic acid (ABA), which is synthesized from xanthophyll pigments. Despite the fact that there is strong evidence of increases in ABA concentrations under various environmental stresses, information concerning the effects of exogenous ABA applications on leaf pigments and fruit carotenoids in tomato (Solanum lycopersicum) is lacking. This study investigated the impacts of root tissue ABA applications on tomato leaf and fruit pigmentation concentrations of ‘MicroTina’ and ‘MicroGold’ tomato plants. Tomato plants were treated with increasing concentrations of ABA in the nutrient solution. Therefore, the purpose of this study was to determine dose–response effects of ABA treatment in solution culture for maximum leaf pigmentation and fruit carotenoids in two distinct genotypes of dwarf tomato. Because ABA is a product of the carotenoid biosynthetic pathway, we hypothesized that applications of ABA treatments would have a positive impact on leaf chlorophylls and carotenoids. Applications of ABA treatments may also have a positive impact on tomato fruit carotenoids. The results indicated that ‘MicroTina’ plants treated with ABA (0.5, 5.0, and 10.0 mg·L−1) had a significant increase in β-carotene [BC (P ≤ 0.001)], lutein [LUT (P ≤ 0.001)], zeaxanthin [ZEA (P ≤ 0.05)], and neoxanthin [NEO (P ≤ 0.001)] in the leaf tissue. In ‘MicroGold’ tomato plants, carotenoids responded similarly. For example, there were significant increases in BC (P ≤ 0.01), LUT (P ≤ 0.001), ZEA (P ≤ 0.05), and NEO (P ≤ 0.001). In ‘MicroTina’ tomato leaves, there were significant increases in chlorophyll a [Chl a (P ≤ 0.001)] and chlorophyll b [Chl b (P ≤ 0.001)] concentrations. Furthermore, there were significant increases in Chl a (P ≤ 0.001) and Chl b (P ≤ 0.001) in ‘MicroGold’ leaf tissue. In ‘MicroTina’ tomato fruit tissue, the concentration increased significantly for lycopene [LYCO (P ≤ 0.01)]. However, in ‘MicroGold’, there were no significant changes in BC and LUT concentrations. In addition, LYCO was found to be below detection limits in ‘MicroGold’ tomato fruit. Therefore, ABA has been shown to positively change tomato leaf pigments in both genotypes and fruit tissue carotenoid concentrations in ‘MicroTina’ tomato.
Mark G. Lefsrud, Dean A. Kopsell, David E. Kopsell, and Joanne Curran-Celentano
Crop plants are adversely affected by a variety of environmental factors, with air temperature being one of the most influential. Plants have developed a number of methods in the adaptation to air temperature variations. However, there is limited research to determine what impact air temperature has on the production of secondary plant compounds, such as carotenoid pigments. Kale (Brassica oleracea L.) and spinach (Spinacia oleracea L.) have high concentrations of lutein and β-carotene carotenoids. The objectives of this study were to determine the effects of different growing air temperatures on plant biomass production and the accumulation of elemental nutrients, lutein, β-carotene, and chlorophyll pigments in the leaves of kale and spinach. Plants were grown in nutrient solutions in growth chambers at air temperatures of 15, 20, 25, and 30 °C for `Winterbor' kale and 10, 15, 20, and 25 °C for `Melody' spinach. Maximum tissue lutein and β-carotene concentration occurred at 30 °C for kale and 10 °C for spinach. Highest carotenoid accumulations were 16.1 and 11.2 mg/100 g fresh mass for lutein and 13.0 and 10.9 mg/100 g fresh mass for β-carotene for the kale and spinach, respectively. Lutein and β-carotene concentration increased linearly with increasing air temperatures for kale, but the same pigments showed a linear decrease in concentration for increasing air temperatures for spinach. Quantifying the effects of air temperature on carotenoid accumulation in kale and spinach, expressed on a fresh mass basis, is important for growers producing these crops for fresh markets.
Dean A. Kopsell, Carl E. Sams, T. Casey Barickman, Dennis E. Deyton, and David E. Kopsell
Selenium (Se) is an essential mammalian micronutrient. Adult humans have a daily requirement of 55 to 70 μg/day Se depending on sex and pregnancy/lactation for females. In addition, recent studies have shown health benefits with dietary Se supplementation of 100 to 200 μg/day Se. However, daily intakes in humans greater than 900 μg Se will result in toxicity called selenosis. Although not essential in plant nutrition, some species can bioaccumulate Se. Brassica and Allium species became prime candidates for Se enrichment because of their ability to accumulate and tolerate high concentrations of Se in edible tissues; however, there is now concern that these species are too efficient at selenization and overconsumption of their selenized tissues could result in selenosis. Herbal crop species are consumed regularly in the diet for their culinary flavor attributes. Basil (Ocimum basilicum L.) and cilantro (Coridandrum sativum L.) are not classified as Se accumulators. Therefore, a study was undertaken to determine the potential to selenize basil and cilantro through foliar Se applications to consistently supplement diets with nutritionally beneficial levels of Se. Plants of each species were grown in both growth chamber and field environments and treated with foliar applications (5 mL per plant) of selenate-Se and selenite-Se at concentrations of 0, 2, 4, 8, 16, and 32 mg·L−1 Se. Crops received three separate foliar applications at ≈5-day intervals beginning 24 to 28 days after planting for the growth chamber plants and 50 days after planning for the field environment. Selenium accumulation in both basil and cilantro leaf tissues increased linearly under both selenate-Se (P ≤ 0.001) and selenite-Se (P ≤ 0.001) foliar treatments in growth chamber and field evaluations. Maximum Se leaf tissue concentrations for basil and cilantro ranged from 13 to 55 μg·g−1 Se dry weight. Selenization of basil and cilantro is possible through foliar Se applications, and Se fortification of herbal crops may provide alternative delivery systems in human diets.
Dean A. Kopsell, Kimberly J. Whitlock, Carl E. Sams, and David E. Kopsell
Purslane (Portulaca oleracea) is a succulent weedy annual in much of the United States. In other parts of the world, purslane is grown as a specialty crop, valued for its nutritional quality. As a leafy crop, purslane contributes carotenoid phytochemicals in the typical Mediterranean diet. Nitrogen (N) influences plant growth and alters pigment composition and accumulation. However, little is known about the impact N fertility may have on pigment concentrations in purslane shoot tissues. The objective of this study was to evaluate the influence of N fertility levels on biomass and concentrations of nutritionally important carotenoid and chlorophyll pigments in purslane. Green Leaf and Golden Leaf purslane cultivars were grown in nutrient solution culture under N concentrations of 13, 26, 52, or 105 mg·L−1. Plants were harvested at 45 days after planting (DAP), and measured for concentrations of shoot pigments using high-performance liquid chromatography (HPLC) methodology. There was no influence of N treatment concentration on purslane shoot tissue fresh weight (FW) accumulation. Nitrogen treatment significantly influenced shoot tissue β-carotene (BC), lutein (LUT), neoxanthin (NEO), total carotenoids, chlorophyll a, chlorophyll b, total chlorophyll, and the chlorophyll a to b ratio in purslane shoot tissues. Concentrations of LUT, NEO, violaxanthin (VIO), chlorophyll b, total xanthophyll cycle pigments, and the chlorophyll a to b ratio differed between the purslane cultivars. Increases in N concentrations acted to increase concentrations of nutritionally important shoot tissue carotenoid pigments in only the Green Leaf purslane cultivar. Therefore, N fertility management and cultivar selection should be considered when producing purslane as a nutritious specialty vegetable crop.
Dean A. Kopsell, David E. Kopsell, Mark G. Lefsrud, Joanne Curran-Celentano, and Laura E. Dukach
Green leafy vegetables are important sources of dietary carotenoids, and members of Brassica oleracea L. var. acephala rank highest for reported levels of lutein and β-carotene. Twenty-three leafy B. oleracea cultigens were field grown under similar fertility over two separate years and evaluated for leaf lutein and β-carotene accumulation. Choice of B. oleracea cultigen and year significantly affected carotenoid levels. Lutein concentrations ranged from a high of 13.43 mg per 100 g fresh weight (FW) for B. oleracea var. acephala `Toscano' to a low of 4.84 mg/100 g FW for B. oleracea var. acephala 343-93G1. β-carotene accumulations ranged from a high of 10.00 mg/100 g FW for B. oleracea var. acephala `Toscano' to a low of 3.82 mg/100 g FW for B. oleracea var. acephala 30343-93G1. Carotenoid concentrations were significantly higher in year 2 than in year 1, but rank order among the cultigens for both lutein and ß-carotene did not change between the years. During each year, there were high correlations between leaf carotenoid and chlorophyll pigments. Under similar growing conditions, choice of B. oleracea cultigen will influence carotenoid accumulation, and this may affect the health benefits of consuming these leafy green vegetable crops.
Dean A. Kopsell, J. Scott McElroy, Carl E. Sams, and David E. Kopsell
Vegetable crops can be significant sources of nutritionally important dietary carotenoids, and Brassica are sources that also exhibit antioxidant and anticarcinogenic activity. The family Brassicaceae contains a diverse group of plant species commercially important in many parts of the world. The six economically important Brassica species are closely related genetically. Three diploid species (B. nigra, B. rapa, B. oleracea) are the natural progenitors of the amphidiploid species (B. juncea, B. napus, B. carinata). The objective of this study was to characterize the accumulation of important dietary carotenoid pigments among the genetically related Brassica species. High-performance liquid chromatographic quantification revealed significant differences in carotenoid and chlorophyll pigment concentrations among the Brassica species. Brassica rapa accumulated the highest concentrations of antheraxanthin [0.79 mg/100 g fresh weight (FW)], lutein (8.89 mg/100 g FW), and zeaxanthin (0.75 mg/100 g FW). The highest concentrations of β-carotene (4.41 mg/100 g FW) and total chlorophyll (125.9 mg/100 g FW) were found in B. juncea. Brassica nigra accumulated the highest concentrations of 5,6-epoxylutein (0.41 mg/100 g FW) and violaxanthin (2.28 mg/100 g FW), whereas B. oleracea accumulated the highest concentrations of neoxanthin (2.10 mg/100 g FW). For many of the pigments analyzed, the amphidiploids B. carinata and B. napus accumulated significantly less carotenoid concentrations than the diploid species and B. juneca. Brassica convey unique health attributes when consumed in the diet. Identification of genetic relationships among the Brassica species would be beneficial information for improvement programs designed to increase carotenoid values.