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  • Author or Editor: Mark Lefsrud x
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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.

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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.

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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.

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