David E. Kopsell

Variability in Elemental Accumulations Among Leafy Brassica oleracea Cultivars and Selections

Abstract The vegetable brassicas are consumed in part for their nutritional values of calcium (Ca), magnesium (Mg), potassium (K), iron (Fe), and zinc (Zn). However, information on the genetic variability of elemental accumulation within kale and collards (Brassica oleracea L. var. acephala DC) is limited. Therefore, 22 kale and collard cultivars and selections suitable for the northeastern United States were field grown under similar fertility regimes over two years and evaluated for elemental accumulation. Leaf tissues were analyzed using inductively coupled argon plasma–atomic emission spectrometry. Significant variability among cultivars and selections was observed for tissue Ca, Mg, K, Fe, and Zn. On average, a two-fold difference in elemental accumulation among the cultivars and selections was measured. Tissue Ca levels ranged from 1.2 (“Crimson Garden”) to 3.1% (“NZ Thousand Head”), tissue Mg ranged from 0.3 (“Crimson Garden”) to 0.6% (“NZ Thousand Head”), tissue K ranged from 2.1 (“NZ Thousand Head”) to 3.5% (30665-96G11), tissue Fe ranged from 53.1 (“Winterbor F1”) to 114.2 mg/kg (“Giant Jersey Kale”), and tissue Zn ranged from 29.1 (“Shetland”) to 71.9 mg/kg (“Redbor F1”). Significant year-to-year variability occurred for Ca, Mg, Fe, and Zn accumulation. Despite these yearly changes, ranking of the cultivars and selections for elemental accumulation, as determined by Spearmans rank correlation coefficient, did not change from year 1 to year 2. Overall, the cultivar with the highest elemental leaf accumulation was “Redbor F1”. Information on genotypic variability for elemental accumulation may be important for producers and consumers looking to select kale and collards with higher nutritional levels of beneficial dietary elements.

Nitrogen Concentration Affects Nutrient and Carotenoid Accumulation in Parsley

ABSTRACT Previous research has suggested that the herbal crop parsley (Petroselinum crispum Nym.) has a relatively high concentration of nutritionally important carotenoid phytonutrients, such as lutein-zeaxanthin and β -carotene. Nitrogen (N) has the most direct impact on plant growth, but influence of N on phytonutritional quality is contradictory. Therefore, the objectives of this study were to measure the effects of different concentrations of N on growth, elemental accumulation, and carotenoid production in parsley. ‘Dark Green Italian’ parsley was greenhouse-grown in a nutrient solution with 6.0, 13.1, 26.3, 52.5, or 105.0 mg N L−1. After 8 weeks, plants were harvested and analyzed for biomass production, micro- and macronutrient concentrations, and lutein-zeaxanthin and β -carotene levels. Increasing N in the nutrient solution increased plant biomass, leaf tissue N, phosphorus (P), potassium (K), lutein-zeaxanthin, β -carotene, and chlorophyll. Leaf iron (Fe), manganese (Mn), and molybdenum (Mo) decreased with increases in N in nutrient solutions. Quadratic increases in response to increasing solution N occurred for leaf calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), and zinc (Zn). Increasing the elemental and carotenoid concentrations in parsley through N fertility modification would be expected to increase the nutritional value of this culinary herbal crop.

Nitrogen Levels Influence Biomass, Elemental Accumulations, and Pigment Concentrations in Spinach

ABSTRACT Spinach (Spinacia oleracea L.) has one of the highest United States per capita consumption rates among leafy vegetable crops, and also ranks second for lutein and β-carotene carotenoid concentration. The objectives of this study were to determine the effects of nitrogen (N) concentration on elemental and pigment accumulation in spinach. Two spinach cultivars (‘Melody’ and ‘Springer F1’) were greenhouse grown in nutrient solution culture under N treatments of 13, 26, 52, and 105 mg L− 1. Leaf tissue biomass increased from 45.6 to 273.2 g plant− 1 and from 127.0 to 438.6 g plant− 1 as N increased from 13 to 105 mg L− 1 for ‘Springer F1’ and ‘Melody’, respectively. Leaf tissue N, phosphorus (P), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn) responded to N treatments. Lutein accumulations, expressed on a fresh weight basis, responded quadratically to increasing N treatments for ‘Springer F1’. Maximum lutein values were 110 and 76 μ g g− 1 on a fresh weight basis, and maximum β-carotene values were 85 and 57 μ g g− 1 on a fresh weight basis for ‘Springer F1’ and ‘Melody’, respectively. Interestingly, N levels had a significant effect on carotenoid accumulation in both ‘Springer F1’ and ‘Melody’ when the pigments were expressed on a dry weight basis. Leaf tissue lutein increased from 0.59 to 1.06 mg g− 1 and from 0.59 to 0.90 mg g− 1 on a dry weight basis with increasing N treatments for ‘Springer F1’ and ‘Melody’, respectively. Reporting lutein and β-carotene on both a fresh and dry weight basis may be the most accurate way to express the carotenoid values of spinach.

Nitrogen and sulfur influence nutrient usage and accumulation in onion

Abstract To study the effects of nitrogen (N) and sulfur (S) fertility on onion (Allium cepa L.) bulb pungency, bulb fresh and dry weight, nutrient uptake and accumulation in the bulb, “Granex 33” onions were greenhouse grown using nutrient solution culture. A factorial arrangement of solutions containing 1.7, 15.0, and 41.7 mg L−1 S and 10, 50, 90, and 130 mg L−1 N were used. Bulb pungency and bulb fresh and dry weight were affected by both S and N treatments. Depletion patterns for most of the macronutrients from the nutrient solutions during plant growth were affected by N and S levels, and differed depending on the N and S combination. In certain N and S combinations, magnesium (Mg) and calcium (Ca) usage were unaffected over time. Bulb N levels increased with N fertility and decreased slightly with S availability, while bulb phosphorous levels responded linearly to N fertility. Overall changes in bulb Ca and Mg levels were minor, but were influenced by N and S fertility. Bulb S content was affected by low S and N fertility, decreasing with each. Boron levels in onion bulbs decreased with increasing N and S fertility, while bulb manganese, iron, and zinc concentrations tended to increase with increasing N availability and decrease with increasing S. Potassium, copper, and molybdenum bulb concentrations were unaffected by N or S fertility. These results have the potential of being used as a reference in developing nutritional programs designed for optimal onion performance having specific flavor intensities.

Increase in Nutritionally Important Sweet Corn Kernel Carotenoids following Mesotrione and Atrazine Applications

The herbicide mesotrione inhibits a critical enzyme, phytoene desaturase, in plant carotenoid biosynthesis. Mesotrione is currently labeled for selective weed control in sweet corn ( Zea mays var. rugosa). Mesotrione applied alone, or in mixtures with the photosystem II inhibitor atrazine, acted to increase concentrations of kernel antheraxanthin, lutein, and zeaxanthin carotenoids in several sweet corn genotypes. Kernel lutein and zeaxanthin levels significantly increased 15.6% after mesotrione + atrazine early postemergence applications, as compared to the control treatment. It appears that mesotrione applications resulted in greater pools of kernel carotenoids once the sweet corn genotypes expressing moderate injury overcame the initial herbicidal photo-oxidative stress. This is the first report of herbicides directly up-regulating the carotenoid biosynthetic pathway in corn kernels, which is associated with the nutritional quality of sweet corn. Enhanced accumulation of lutein and zeaxanthin is important because dietary carotenoids function in suppressing aging eye diseases such as macular degeneration, now affecting 1.75 million older Americans.

Carotenoids in Vegetables: Biosynthesis, Occurrence, Impacts on Human Health, and Potential for Manipulation

Publisher Summary This chapter illustrates the current knowledge of carotenoid chemistry, bioavailability assessments, the impacts of certain carotenoids on human health and disease suppression, how pre- and post-harvest cultural practices can alter carotenoid levels and influence potential bioavailability, and current vegetable carotenoid enhancement efforts. Consumption of vegetables provides the human diet with many essential vitamins and minerals important for health maintenance. Vegetables also contain secondary metabolite phytochemicals, which provide benefits beyond normal health maintenance and nutrition and play active roles in chronic disease reductions. One important class of phytochemicals is the carotenoids. Carotenoids are lipid-soluble pigments found in all photosynthetic organisms. Among the naturally occurring plant pigments, carotenoids are widely distributed, demonstrate a high degree of structural diversity, and possess large variations in biological functions. The many health benefits attributed to carotenoid intake include prevention of certain cancers, cardiovascular diseases, and aging eye diseases, as well as enhanced immune system functions. Pro-vitamin A activity is the classical biological function of carotenoids in mammalian systems. Research into carotenoid enhancement of vegetable crops to benefit human health has paralleled efforts to increase consumption of fruits and vegetables in the diet. Release of carotenoid compounds from the membranes of plant tissues facilitates intestinal absorption; however, changes in carotenoid chemistry by biotic and abiotic factors can influence bioavailability. Current methods to assess bioavailability include serum measurements and in vitro digestion models.

UV-B Radiation Impacts Shoot Tissue Pigment Composition in Allium fistulosum L. Cultigens

Plants from the Allium genus are valued worldwide for culinary flavor and medicinal attributes. In this study, 16 cultigens of bunching onion (Allium fistulosum L.) were grown in a glasshouse under filtered UV radiation (control) or supplemental UV-B radiation [7.0 μmol·m−2 ·s−2 (2.68 W·m−2)] to determine impacts on growth, physiological parameters, and nutritional quality. Supplemental UV-B radiation influenced shoot tissue carotenoid concentrations in some, but not all, of the bunching onions. Xanthophyll carotenoid pigments lutein and β-carotene and chlorophylls a and b in shoot tissues differed between UV-B radiation treatments and among cultigens. Cultigen “Pesoenyj” responded to supplemental UV-B radiation with increases in the ratio of zeaxanthin + antheraxanthin to zeaxanthin + antheraxanthin + violaxanthin, which may indicate a flux in the xanthophyll carotenoids towards deepoxydation, commonly found under high irradiance stress. Increases in carotenoid concentrations would be expected to increase crop nutritional values.

RATIO OF CALCIUM TO MAGNESIUM INFLUENCES BIOMASS, ELEMENTAL ACCUMULATIONS, AND PIGMENT CONCENTRATIONS IN KALE

Producers use elemental ratios, such as calcium (Ca): magnesium (Mg), in fertility programs to ensure sufficient nutrient uptake. Kale (Brassica oleracea L. var. acephala D.C.) accumulates high levels of carotenoids which can be beneficial for human health. Objectives were to determine the influence of Ca:Mg fertilization on 1) biomass, 2) essential nutrients, and 3) carotenoids in kale leaf tissues. ‘Redbor’ kale was greenhouse-grown in solution culture. Ca:Mg ratio treatments were 9:1, 6:1, 3:1, 1:3, 1:6, and 1:9. Ca:Mg ratio significantly affected biomass, nutrient accumulation, and carotenoids. Plant biomass decreased linearly (P ≤ 0.001) and β-carotene, lutein, neoxanthin, and antheraxanthin all increased, then decreased quadratically (P ≤ 0.001) as the ratio of Ca:Mg changed from 9:1 to 1:9. Ca:Mg ratio also affected leaf tissue Ca, Mg, potassium (K), sulfur (S), boron (B), manganese (Mn), molybdenum (Mo) and zinc (Zn). Results indicate that producers wishing to maximize elemental uptake and carotenoid content of kale need to consider the ratio of Ca:Mg in their fertility programs.

Seed Germination Response of Rapid-Cycling Brassica oleracea Grown Under Increasing Sodium Selenate

Abstract Breeding plants to be more efficient at micronutrient accumulation is a proposed strategy for fighting worldwide malnutrition of humans. Selection for increased selenium (Se) in Brassica oleracea L. is possible. However, when present at high levels, micronutrients such as Se can affect seed germination and subsequently hamper breeding efforts. The objectives of this study were: (1) to evaluate the accumulation of Se in seeds of B. oleracea; and (2) to determine effects that Se accumulation may have on seed germination. Plants of a rapid‐cycling B. oleracea population were grown in nutrient solutions with sodium selenate (Na2SeO4) concentrations up to 7 mg L−1 (2.93 mg Se L−1). Seeds and leaves were harvested from the selenized plants and analyzed for Se content using atomic absorption spectrophotometry. Germination percentage and rate were determined by sowing seeds in moistened towels, placing them in an incubator at 21°C, and observing radicle emergence. Selenium accumulated in the seeds, but at a lower level than in the leaves. Seed Se content increased linearly with increasing Na2SeO4 in solution culture. A significant difference in germination percentage occurred if Na2SeO4 was in solution at 5 mg L−1 or higher. However, even at the higher selenate treatments, germination percentage never fell below 94%. Germination rate was little affected by the Se content in the seeds. These observations provide evidence that Se accumulation in seeds is not likely to hamper breeding efforts for Se enrichment in B. oleracea at Se levels similar to this study.

SELENIUM FERTILIZATION INFLUENCES BIOMASS, ELEMENTAL ACCUMULATIONS, AND PHYTOCHEMICAL CONCENTRATIONS IN WATERCRESS

Watercress (Nasturtium officinale R. Br.) produces carotenoids and sulfur-containing glucosinolates (GSs) beneficial to human health. Selenium (Se) imparts dietary health properties and substitutes for S in plant biochemical pathways. Experimental objectives were to determine the influence of Se fertilization on 1) biomass, 2) elemental accumulations, 3) carotenoids, and 4) glucosinolates in watercress leaf and shoot tissues. Watercress was greenhouse grown in solution culture with Se treatments of 0, 0.125, 0.25, 0.50, 1.0, 2.0, and 4.0 mg Se L−1, delivered as sodium selenate (Na2SeO4). Fresh and dry biomass were unaffected while shoot tissue Se (P = 0.057) and S (P = 0.003) increased linearly in response to increasing Se treatments. Linear decreases were measured for β-carotene (P = 0.017) and lutein (P = 0.018) in response to increasing Se. Total levels of GS increased, then decreased quadratically (P = 0.003). Results indicate that Se supplementation can increase Se tissue concentrations and GS in watercress; however, carotenoids were negatively affected.