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V.M. Russo, J. Williamson, K. Roberts, J.R. Wright, and N. Maness

Sugars move through stalks to be deposited in kernels in sweet corn (Zea mays L.). Concentrations of sugars in stalks change as plants pass through developmental stages. To follow such changes, carbon-13 nuclear magnetic resonance spectroscopy (C-nmr), a technology that can measure concentrations of sugars in tissues, was compared with analysis by high-performance liquid chromatography (HPLC). A shrunken-2 hybrid (cv. Illini Gold), was monitored from mid-whorl to fresh-market maturity (R3). Internodes near the base of the stalk, just below the ear, and between an ear and the tassel were sampled at each developmental stage. Chemical shifts in C-nmr spectra were measured in parts per million hertz (ppm) down-field relative to tetramethyl silane. Through silk emergence (R1) C-nmr spectra were similar regardless of internode, having line positions between 60 and 105 ppm. Unique lines for glucose, fructose, and sucrose were at 96, 98, and 104 ppm, respectively, and mole fractions were similar to those determined by HPLC. The highest concentrations were recorded at R1 for sucrose (26.1 mg·mL-1), from tasseling (VT) through R3 for fructose (avg. 30.4 mg·mL-1), and from VT to R1 for glucose (avg. 32 mg·mL-1). Carbon-13 nuclear magnetic resonance spectroscopy can be used, with minimal sample handling, to monitor sugar concentrations in sweet corn.

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Cheng Bai, Charles C. Reilly, and Bruce W. Wood

While nickel (Ni) deficiency occurs in certain agricultural crops, little is known regarding the influence of deficiency on metabolic or physiological processes. We studied the influence of Ni deficiency on the reduced-nitrogen (N) composition of early spring xylem sap of pecan [Carya illinoinensis (Wangenh.) C. Koch]. High-performance liquid chromatography (HPLC) analysis of sap composition found the presence of ureido-, amide-, and amino-N substances and that they are quantitatively influenced by tree Ni nutritional status. Ureido-N forms quantitatively dominated amide-N forms with respect to both molar concentration and the forms in which reduced N atoms are present; thus, pecan appears to be predominately a ureide-transporting species. The primary ureido-N substances in sap of Ni-sufficient trees are citrulline ≈ asparagine ≈ xanthine > ureidoglycolate > allantoic acid > allantoin ≈ uric acid ≈ urea. Asparagine is the primary amide-N form, while only traces of amino-N forms (e.g., tryptamine and β-phenylethylamine) are found in xylem sap. Nickel deficiency substantially increased citrulline and allantoic acid in xylem sap while decreasing the asparagine, xanthine, and β-phenylethylamine concentrations. These Ni-linked quantitative shifts in reduced-N forms indicate that Ni nutrition potentially affects intermediates of both the ureide catabolic pathway and the urea cycle as well as the nitrogen/carbon (N/C) economy of the tree. Xylem sap-associated urease-specific activity was also reduced as a consequence of Ni deficiency. These results indicate that Ni deficiency potentially disrupts normal N-cycling via disruption of ureide metabolism.

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Bhimanagouda S. Patil, Leonard M. Pike, and Kil Sun Yoo

The aglycone, or free quercetin, and total quercetin content of 75 cultivars and selections was analyzed by reverse-phase high-performance liquid chromatography. Quercetin glycosides were hydrolyzed into aglycones. Total quercetin content in yellow, pink, and red onions varied from 54 to 286 mg·kg-1 fresh weight in different onion entries grown during 1992. White onions contained trace amounts of total quercetin. Free quercetin content in all the onions was low (< 0.4 mg·kg-1) except in `20272-G' (12.5 mg·kg-1 fresh weight). Bulbs stored at 5, 24, and 30C and controlled atmosphere (CA) for 0,1,2,3,4, and 5 months showed a most marked change in total quercetin content at 24C compared to other treatments, with a rise in mid-storage followed by a drop. Storage at 5 and 30C also demonstrated a similar change. However, total quercetin content did not vary significantly in bulbs stored at CA for 5 months. We conclude that genetic and storage factors affect quercetin content on onions.

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Md. Shahidul Islam, M. Jalaluddin, James O. Garner, M. Yoshimoto, and O. Yamakawa

Sweetpotato leaves contain biologically active anthocyanins that have significant medicinal value for certain human diseases and may also be used as natural food colorants. Foliar anthocyanins and their relative abundance were investigated in leaves of sweetpotato cultivars `Shimon-1', `Kyushu-119', and `Elegant Summer' grown under artificial shading and different temperature conditions. High-performance liquid chromatography profiles of the cultivars tested showed similar peaks but with peak areas differing with cultivar, temperature and shading. The relative quantity of individual anthocyanin was YGM (Yamagawamurashaki)-1a> YGM-4b> YGM-1b> YGM-5a> YGM-0d> YGM-0a> YGM-2> YGM-0c> YGM-3> YGM-6> YGM-5b> YGM-0b> YGM-0f> YGM-0e> YGM-0g. Seven were peonidin and eight cyanidin derivatives. The highest anthocyanin contents were found in plants grown at a moderate temperature (20 °C) with lower levels at 25 and 30 °C. The leaves of plants grown in full sun accumulated significantly more total as well as the major individual anthocyanins than plants grown in 40% and 80% shade. The results indicate that growing sweetpotatoes at moderate temperatures and without shading facilitates the accumulation of anthocyanins in the leaves. The anthocyanin composition of the leaves is discussed relative to their physiological function in human health.

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Patrick J. Conner and Dan MacLean

Anthocyanin content and composition and CIE 1976 (L*, a*, b*) color space (CIELAB) color coordinates were examined for the skin of 22 muscadine grape (Vitis rotundifolia Michx.) cultivars and Muscadinia Planch germplasm. Analysis of berry skin extracts by high-performance liquid chromatography (HPLC) determined that anthocyanin content varied from less than 100 μg·g−1 in bronze and pink berries to over 5500 μg·g−1 in highly pigmented black berries. The anthocyanins delphinidin, cyanidin, petunidin, pelargonidin, peonidin, and malvidin were detected in their 3,5-diglucosidic forms. Analysis of berry color with a colorimeter revealed chroma (C*) ranged from 2.4 to 22.8 with the highest values occurring in bronze- and red-colored berries. As anthocyanin concentration increased, lightness (L*) decreased to a low of 20 to 23 in black-colored berries. Pink and red skin colors were primarily a result of lower levels of total anthocyanins, although there was also a shift away from delphinidin and petunidin production toward more cyanidin and peonidin. Malvidin, the most important anthocyanin for muscadine wine and juice color stability, was only abundant in a few clones, all of which had V. munsoniana (Simpson ex Munson) Small or V. popenoei (Fennell) Small in their pedigree. The interspecific hybrid ‘Fennell’s 3-way Hybrid’ had the largest proportion of malvidin, contributing ≈58% of the total anthocyanin content. This clone also had low levels of delphinidin and high total levels of anthocyanin, making it a promising source for the improvement of muscadine grape pigment profiles.

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Adnan Nurhan Yildirim, Fatma Akinci-Yildirim, Mehmet Polat, Bekir Şan, and Yılmaz Sesli

Amygdalin is a bioactive compound used in the traditional treatment of some diseases, and it is toxic to humans and animals when it is consumed excessively. It is abundantly found in the kernels of almond cultivars, especially in bitter ones. In the study, the amygdalin contents of the kernels of 15 commercial almond cultivars (Prunus amygdalus L.) were determined by high-performance liquid chromatography (HPLC) for 2 consecutive years. The seeds of the cultivars were obtained from the Fruit Research Institute, Isparta, Turkey. Results indicated that amygdalin concentrations of the cultivars were significantly different (P < 0.05) for 2 years. The levels amygdalin ranged from 0.443 g·kg–1 to 1.866 g·kg–1 in 2008 and from 0.250 g·kg–1 to 2.200 g·kg–1 in 2009. As the average of 2 years, the highest concentration of amygdalin was determined in ‘Supernova’ (1.458 g·kg–1) and the lowest concentration was determined in ‘Masbovera’ (0.370 g·kg–1).

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Abraham J. Escobar-Gutiérrez and Jean-Pierre Gaudillére

The aim of this study was to investigate variability in the sorbitol: sucrose ratio (SSR) in source leaves of different peach [Prunus persica (L.) Batsch] cultivars. Four- and 5-year-old trees of 58 cultivars were examined. Mature leaves were sampled on three dates in middle to late summer and analyzed for neutral soluble sugars using high-performance liquid chromatography. Differences in SSRs were observed. In most cultivars, the sorbitol content was at least twice that of sucrose. The maximal range of SSR occurred on the third date and ranged from 1.5 to 4.3. There was a date × genotype interaction (P < 0.01). When cultivars were grouped by country of origin, the mean ratios of the Japanese group were lower than those of the Italian and American groups for all three sampling dates. The SSRs of nectarines were higher than those of peach and canning clingstone-type cultivars. In general, variations in SSR were due mostly to differences in sucrose content. The SSR was negatively correlated with flowering date. These results indicate variability in SSR in peach germplasm, variability that seems to be related to the geographical origin of the cultivars.

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Murshidul Hoque*, Husein Ajwa, and Beiquan Mou

Lettuce (Lactuca sativa L.) is an essential salad crop in the American diet. Nitrogen (N), phosphorus (P), and potassium (K) are required for successful lettuce production and can influence lettuce quality. The objective of the study was to evaluate changes in nutritional composition of romaine (`Green Tower') and iceberg (`Sharp Shooter') lettuce in responses to N, P and K fertilization during fall production in Salinas, Calif. Sixteen treatment combinations of fertilizer were selected to provide a range of treatments. N was applied at 0, 112, 225, and 338 kg·ha-1 as ammonium nitrate; P was applied at 0, 112, and 225 kg/ha as super phosphate; and K was applied at 0 and 112 kg·ha-1 as muriate of potash. Nutritional content of fresh tissue of two types of lettuce was analyzed using high performance liquid chromatography (HPLC). Among the parameters analyzed were lutein, beta-carotene, chlorophyll a, and chlorophyll b. Yield was increased with increasing N fertilizer level, but was not affected by P or K application rates. The best post harvest quality, however, was at moderate P application rate. Increasing the N and P rates gradually increased glucose content in lettuce but decreased the shelf life. Significant differences between the two types of lettuce were found in chlorophyll, lutein and beta-carotene content. No significant correlations were found between soil fertilizer application levels and nutritional content of lettuce. However, the ratio of chlorophyll a and b were greater with the increase of fertilizer rate. Nutritional composition including vitamin C will be presented.

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Md. Shahidul Islam, Makoto Yoshimoto, Koji Ishiguro, Shigenori Okuno, and Osamu Yamakawa

The phenolic content and the radical scavenging activity were compared in leaves of sweetpotato (Ipomoea batatas L.) cultivars Shimon-1, Kyushu-119 and Elegant Summer grown under different temperature and shading conditions. Compared to cultivar differences, there was less effect of temperature and shading on the total phenolic content in sweetpotato leaves, however certain polyphenolic components differed widely among the treatments. The positive correlation between the radical scavenging activity and the level of total phenolics (r = 0.62) suggests that phenolic compounds are important antioxidant components of sweetpotato leaves. All the reverse-phase high-performance liquid chromatography (RP-HPLC) profiles of the cultivars tested showed peaks at the same retention times but peak areas of individual phenolic compounds differed with respective temperature and shading treatments. The phenolic compounds identified in the sweetpotato leaf were caffeic acid, chlorogenic acid, 4,5-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid, and 3,4,5-tri-O-caffeoylquinic acid. Most of the phenolic compounds were highest in leaves from plants grown at 20 °C without shading except 4,5-di-O-caffeoylquinic acid. The results indicate that growing leaves under moderately high temperatures and in full sun enhances the accumulation of phenolic components. These phenolic components have possible value in enhancing human health.

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Sonja L. Maki and Nihal C. Rajapakse

Endogenous gibberellins of chrysanthemum [Dendrathema×grandiflorum (Ramat) cv. Bright Golden Anne] were characterized in preparation for quantification of endogenous gibberellins in apices under control and CuSO4 spectral filters. Expanding shoots were separated into young expanding leaves and apices. Methanolic extracts of young expanding leaves were purified by solvent partitioning, PVPP column chromatography, and reversed-phase high performance liquid chromatography. Two bioactive regions corresponding to the HPLC retention times of GA and GA19 standards were detected in fractions using the recently developed non-dwarf rice bioassay. Dideuterated internal standards of GA12, GA53, GA19, GA20, and GA1 were added to similar extracts of shoot apices. The presence of endogenous GA53, GA19, GA20, and GA1 in chrysanthemum apices was confirmed by isotope dilution using gas chromatography–mass spectrometry-selected ion monitoring and Kovats retention indices. Ions for the deuterated internal standard of GA12 were detected, but not for endogenous GA12. The above results demonstrate that the early 13-hydroxylation pathway operates in chrysanthemum.