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 µ mol·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 ß -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.

Accumulation and bioavailability of dietary carotenoids in vegetable crops.

Carotenoids are lipid-soluble pigments found in many vegetable crops that are reported to have the health benefits of cancer and eye disease reduction when consumed in the diet. Research shows that environmental and genetic factors can significantly influence carotenoid concentrations in vegetable crops, and that changing cultural management strategies could be advantageous, resulting in increased vegetable carotenoid concentrations. Improvements in vegetable carotenoid levels have been achieved using traditional breeding methods and molecular transformations to stimulate biosynthetic pathways. Postharvest and processing activities can alter carotenoid chemistry, and ultimately affect bioavailability. Bioavailability data emphasize the importance of carotenoid enhancement in vegetable crops and the need to characterize potential changes in carotenoid composition during cultivation, storage and processing before consumer purchase.

Kale carotenoids are unaffected by, whereas biomass production, elemental concentrations, and selenium accumulation respond to, changes in selenium fertility.

Selenium (Se) is a micronutrient in mammalian nutrition and is accumulated in kale (Brassica oleracea L. var. acephala), which has high levels of lutein and beta-carotene. Selenium, lutein, and beta-carotene have important human health benefits and possess strong antioxidant properties. The objectives of this study were to determine the influence of different Se [as sodium selenate (Na(2)SeO(4)) and sodium selenite (Na(2)SeO(3))] fertility levels on (1) biomass accumulation, (2) the accumulation patterns of carotenoid pigments, and (3) elemental accumulation in the leaves of kale. Winterbor kale was greenhouse-grown using nutrient solution culture with Se treatment concentrations of 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 mg Se/L as Na(2)SeO(4) and 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mg Se/L as Na(2)SeO(3). Increases in either selenate (SeO(4)(-)(2)) or selenite (SeO(3)(-)(2)) resulted in decreases in kale leaf tissue biomass. Neither of the Se treatments had an effect on the accumulation of lutein or beta-carotene in leaf tissues. Increasing SeO(4)(-)(2) significantly increased the accumulation of kale leaf Se; however, leaf tissue Se did not significantly change over the SeO(3)(-)(2) treatments. Increases in SeO(4)(-)(2) affected the leaf tissue concentrations of P, K, Ca, Mg, S, B, Cu, Mn, and Mo, whereas SeO(3)(-)(2) only affected B and S. Growing kale in the presence of SeO(4)(-)(2) would result in the accumulation of high levels of tissue Se without affecting carotenoid concentrations.

Spinach cultigen variation for tissue carotenoid concentrations influences human serum carotenoid levels and macular pigment optical density following a 12-week dietary intervention.

Increasing intakes of carotenoid-rich plant foods can increase serum carotenoid concentrations and macular pigment optical density (MPOD) in most, but not all, individuals. Research objectives for this study were to (1) characterize tissue lutein (L) and beta-carotene (BC) concentrations in carotenoid-rich spinach (Spinacia oleracea L.) cultigens and (2) determine serum carotenoid and MPOD responses in human subjects consuming spinach cultigens differing in tissue L and BC concentrations. Thirteen spinach cultigens were evaluated for carotenoid accumulations over two consecutive growing seasons. "Springer" (8.4 and 6.5 mg/100 g of fresh mass for L and BC, respectively) and "Spinner" (12.1 and 9.2 mg/100 g of fresh mass for L and BC, respectively) spinach cultigens were selected for a dietary intervention study and represented low- and high-L concentrations. The high-L ("Spinner") and low-L ("Springer" ) spinach treatment groups consisted of 10 subject volunteers ingesting five 50-g spinach servings/week during a 12-week intervention. Average serum L concentrations increased by 22% (P = 0.07) from baseline (0.233 micromol/L) to 12 weeks (0.297 micromol/L) for subjects consuming low-L spinach. Subjects consuming high-L spinach showed increases of 33% (P = 0.04) in serum L from baseline (0.202 micromol/L) to 12 weeks (0.300 micromol/L). Average MPOD did not change for the low-L treatment group; however, subjects in the high-L group demonstrated increases (P = 0.02) in MPOD at the 30' eccentricity between baseline (0.343) and 12 weeks (0.374). This study demonstrates that serum carotenoid and MPOD are determined by L concentrations present in the spinach matrix. Results emphasize the role of cultigen selection among vegetable crops in determining phytochemical effects on human health.

Kale carotenoids remain stable while flavor compounds respond to changes in sulfur fertility.

Dietary intake of certain carotenoids has been associated with a reduced risk of disease. Kale (Brassica oleracea L. Acephala Group) has the highest levels of carotenoids lutein and beta-carotene, and is an excellent source of minerals among the green leafy vegetable crops. However, Brassica vegetables contain glucosinolate (GS) and S-methylcysteine sulfoxide (MCSO). While these sulfur compounds have medicinal value, they are also responsible for the bitter, acrid flavors that are often regarded as objectionable by consumers. Therefore, the objectives of this study were to investigate the influence of increased S fertility levels on (1) elemental accumulation, (2) GS and MCSO production, and (3) the accumulation patterns of carotenoid pigments in the leaves of three kale cultivars. Winterbor, Redbor, and Toscano kale were greenhouse-grown using nutrient solution culture with S treatment concentrations of 4, 8, 16, 32, and 64 mg of S/L. Decreasing S fertility decreased S leaf content, but increased the levels of Mg and Ca accumulation, two important minerals for human health. Levels of GS and MSCO decreased in response to a decreasing S level in nutrient solution. However, accumulation of lutein and beta-carotene was unaffected by S treatment. Lowering the S fertility in the production of kale should decrease the levels of negative flavors associated with high levels of GS and MCSO without affecting carotenoid pigment levels. Understanding the combined impact of fertility on flavor compounds and carotenoid pigments may help improve consumer acceptance of phytonutritionally enhanced vegetable crops.

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.