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Huimin Zhang, Hongguang Yan, Cuixiang Lu, Hui Lin, and Quan Li

differences in the chemical composition of sweet cherry leaves under different cultivation patterns using Nuclear magnetic resonance (NMR) have not been reported. NMR is a powerful and sophisticated technique with a wide range of applications, such as

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R. Roger Ruan, Paul L. Chen, and Simon Almaer

This paper describes the relationship between the maturity stages and nuclear magnetic resonance (NMR) characteristics of sweet corn (Zea mays L.). The NMR parameter T2, which is the spin–spin relaxation time constant, and two conventional maturity parameters, moisture content and alcohol insoluble solids (AIS), of sweet corn samples during maturation, were determined and correlated with reference maturity indices, namely, heat units and sensory maturity scores. The relationships between T2 and the heat unit and sensory maturity score of the samples were linear, suggesting that T2 can be used to establish mathematical models for the prediction of sweet corn maturity to determine harvest time. The major advantages of using NMR are the nondestructive nature, the speed, and the simplicity of the method.

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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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Anne Fennell, Carol Wake, and Paul Molitor

Changes in tissue water content have been correlated, with varying success, with changes in freezing tolerance and dormancy in woody perennials. Recent studies indicate that changes in the state of water are more strongly correlated with dormancy than are changes in bulk water content. In this study, traditional destructive methods of monitoring tissue water content and dormancy were compared with measurements using nondestructive in situ proton nuclear magnetic resonance 1H NMR to determine plant water status. These studies were designed to determine whether changes in bud water status are correlated with dormancy and can be used as a reliable indicator of the onset of dormancy. Two-year-old Vitis riparia plants were subjected to short-day (SD, 8 h daylight) or long-day (LD, 15 h daylight), dormancy-inductive or noninductive treatments, respectively. Bud water was monitored at 2, 4, and 6 weeks of photoperiod treatments. SD treatments promoted a rapid onset in bud dormancy. Water content was not different in SD or LD treatments after 2 weeks. However, it did decrease over 6 weeks in both treatments, but SD treatments promoted a more rapid decrease in water content. The nondestructive 1H NMR methods give comparable measures of water content and provide a measure of bud water status. There were shorter T1 relaxation times in the 2-, 4-, and 6-week SD treatments. The SD treatment T2 relaxation times were shorter in the 4- and 6-week SD treatments only. Changes in the T1 and T2 relaxation times indicated changes in bud water status are correlated with the onset of dormancy.

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Carmen del Río and Ana M Romero

Several experiments showed that whole, unmilled olives (Olea europaea L.) could be dehydrated in 42 hours in a forced-air oven at 105 °C (221 °F), so that they could be used in determining their oil content in a nuclear magnetic resonance (NMR) analyzer. After confirming that the NMR and the official Soxhlet methods estimate the same oil percentages in milled olives, linear regression analysis also showed that NMR provides the same oil percentage results with milled and unmilled fruit. This new method avoids sample manipulation before dehydrating the fruit, making it possible to work with olive samples weighing as little as 70 g (2.47 oz). It allows for processing a large number of samples in a short period of time and may be also used with unmilled fruit flesh. The method is also very useful for screening genotypes, either from germplasm banks or progenies from olive breeding programs, and for evaluating cultivars in comparative trials.

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Marco Beyer, Stefanie Peschel, Moritz Knoche, and Manfred Knörgen

Water uptake in different regions of the sweet cherry fruit (Prunus avium L. cv. Sam) was investigated following selective application of silicone sealant to the pedicel end, pedicel cavity, pedicel/fruit juncture, or stylar scar of detached fruit. The time course of water uptake was monitored gravimetrically during a 3-hour incubation period in deionized water (20 °C). Sealing the pedicel end and/or pedicel/fruit juncture significantly reduced rates and total amount (3 hours) of water uptake, but sealing the stylar scar had no effect. The amount of water penetrating via the pedicel/fruit juncture increased between 50 and 85 days after full bloom. During the same period the maximum force required to detach pedicels from fruit (fruit removal force) fell from 5.2 ± 0.5 to 2.1 ± 0.2 N. The amount of water penetrating via the pedicel/fruit juncture and the fruit removal force were negatively related. Nuclear magnetic resonance (NMR) imaging of mature fruit incubated in D2O indicated that D2O accumulated in the pedicel cavity region and the pedicel. Our data suggest that the pedicel end and pedicel/fruit juncture, but not the stylar scar, are regions of preferential water uptake in detached fruit. Chemical name used: deuterium oxide (D2O).

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Christopher J. Clark and Douglas M. Burmeister

Development of browning induced in `Braeburn' apple (Malus ×domestica Borkh.) fruit by a damaging CO2 concentration was monitored weekly using magnetic resonance imaging (MRI) during a 4-week storage trial (0.5 °C, 2 kPa O2/7 kPa CO2). Discrete patches of high-intensity signal, distributed randomly throughout the fruit, were observed in multislice images of samples after 2 weeks of storage; these patches were eventually confirmed as being sites of browning reactions after dissection at the end of the trial. Subsequently (weeks 3 and 4), signal intensity at sites of incipient damage increased and patches enlarged and coalesced. After 2 weeks of storage, the extent of affected tissue, averaged across all image slices, was 1.5%, increasing to 15.9% and 21.3% after 3 and 4 weeks. The average rate at which tissue damage spread in individual slices was 0.81 (range: 0–3.70) cm2·d–1 between weeks 2 and 3, declining to 0.32 (range: 0–1.55) cm2·d–1 in the final week. Tissue damage induced under these conditions did not spread at the same rate at all locations within individual fruit, nor was it preferentially located toward the stem or calyx ends of the fruit.

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Christopher J. Clark, Annette C. Richardson, and Ken B. Marsh

Whole-fruit proton magnetic resonance (MR) imaging was performed on satsuma mandarin (Citrus unshiu Markovich cv. Miho Wase) during a 15-week period commencing 10 weeks after anthesis and continuing to maturity, and at 6 weeks after anthesis the following season. Images with long repetition times (>1600 ms) and short echo times (20 ms) provided the clearest details of anatomical changes in the peel (flavedo, albedo) and vascular system, while those with similar repetition times but longer echo times (120 ms) were best for viewing juice sac morphology within pulp segments. At 6 weeks after anthesis, images of fruits of slightly different physiological ages highlighted rapid changes in the vascular bundles and albedo tissue at this stage of development. Variation in the relaxation measurements, T1 and T2, was determined from quantitative MR images of the juice sacs in equatorial slices, and images of expressed juice from whole fruit. Seasonal measurements of T1 determined in situ (1760 ms) were significantly greater than those in juice (1413 ms). By contrast, there was no mean seasonal difference between in situ T2 measurements (360 ms) and those for juice (332 ms). No associations between trends in the MR data and total soluble solids, pH, titratable acidity, and sugar and organic acid composition of the juice were established. Cell structure is identified as a hindrance in the use of quantitative MR imaging for probing compositional changes in solution in serial imaging studies.

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B.L. Tan, N. Reddy, V. Sarafis, G.A.C. Beattie, and R. Spooner-Hart

2 NMR and MRI Facility. 3 School of Life Sciences University of Queensland.

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Anne Fennell, Carol Wake, and Paul Molitor

Nuclear magnetic resonance longitudinal (T1) and transverse (T2) times were used to monitor changes in bud water state during the photoperiodic induction of dormancy in grape (Vitis riparia Michx.). Short day (SD) treatments were used to promote a rapid onset of bud dormancy, and long day (LD) treatments were used to prevent the onset of dormancy. Water content (WC) and the state of bud water were monitored after 2, 4, and 6 weeks of LD or SD treatment in three bud developmental stages. There was no difference in WC in the SD and LD treatments after 2 weeks. WC decreased in LD and SD buds of all stages during the 6 weeks of treatments, but there was a greater decrease in WC in SD treatments. The state of bud water changed during the SD treatments, shown in changes in T1 and T2 relaxation times. The SD T1 relaxation times were shorter than the LD T1 values at all measurement times. The SD T2 times were shorter than the LD T2 values in the 4- and 6-week treatment only. Tissue age was an element in lowering the T1 and T2 times but not the primary factor. A comparison between the bud dormancy response in the SD and LD treatments and the relaxation times showed that the shorter relaxation times indicate a restriction of motional freedom. The short relaxation times of the SD treatment correlated with the onset of dormancy. When dormancy is fully induced, T2 times correlated better with dormancy than T1 times.