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Clyde Wilson, Robert A. Clark, and Monica A. Madore

We examined the effect of salt stress on sugar transport across the plasma membrane of source leaf tissue. We initiated the present study by investigating the effect of salt stress on the sugar transport into mature leaf tissue by measuring sucrose influx into leaf discs. In order to determine if there is a common response to salt stress, we selected two species which have been described as moderately salt-sensitive, faba bean and tomato. We found these two plants exhibit different responses to salinity with regard to sugar transport across the plasmalemma. Whereas salinity decreased sucrose uptake into leaf discs of tomato, it had little effect on faba bean. Also, the inhibitory effect of salinity in tomato was not just limited to freshly cut discs but was observed in aged discs as well. We isolated the plasma membrane from tomato and faba bean using the aqueous two-phase technique and found that although plasma-membrane vesicles obtained from faba bean were able to maintain an acetate gradient, vesicles from tomato were not, thereby eliminating any comparative study on pH-dependent sugar uptake. Studies on passive uptake into these vesicles indicate that the passive uptake in tomato may be different than faba bean.

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T.M.M. Malundo, R.L. Shewfelt, G.O. Ware, and E.A. Baldwin

Information on important flavor components for fruit and vegetables is lacking and would be useful for breeders and molecular biologists. Effects of sugar and acid levels on mango (Mangifera indica L.) flavor perception were analyzed. Twelve treatments, identified using a constrained simplex lattice mixture design, were formulated by adding sugar (60%), citric acid (40%), and water to an equal volume of mango homogenate. Using 150-mm nonstructured line scales, a trained panel evaluated the treatments according to 11 flavor descriptors. Titratable acidity (TA), pH, and total soluble solids (TSS) were also determined. Acid concentration affected ratings for sweet, sour, peachy, pine/terpentine, astringent, and biting. Except for sour taste, all descriptors were affected by sugar content while increasing water increased intensities of all flavor notes. TA, pH, and TSS/TA correlated (P < 0.01) with and were useful predictors (r > 0.80) of sour taste and chemical feeling descriptors astringent and biting. TSS, however, was not a particularly good indicator of sweetness (r = 0.72) or any other descriptor except possibly peachy (r = 0.79). It is evident from this study that sugars and acids enhance human perception of specific flavor notes in mango, including aromatics.

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Abby K. van den Berg and Timothy D. Perkins

A field-portable tool for nondestructive foliar anthocyanin content estimation would be beneficial to researchers in many areas of plant science. An existing commercial chlorophyll content meter was modified to measure an index of anthocyanin content. The ability of the experimental anthocyanin meter (ACM) to estimate total extractable anthocyanin content was tested in sugar maple (Acer saccharum Marsh.) leaves representing several subjective color categories collected from a variety of field sites in northwestern Vermont on several dates in Autumn 2003. Overall, there was a significant linear relationship between anthocyanin content index (ACI) and total extractable anthocyanin content (r2 = 0.872, P < 0.001). Therefore, the ACM appears to be an effective tool for estimation of relative anthocyanin content in large samples of autumn sugar maple leaves.

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Yasutaka Kano

higher number of large cells relative to small cells in the fruit. Most of the imported sugars accumulate in the vacuole of sink-tissue storage cells ( Leigh et al., 1979 ; Yamaki and Ino, 1992 ). Cell size during the latter stage of fruit development is

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Jeffrey Adelberg and Matthew Cousins

Geophytes store carbohydrates in modified underground shoot systems protected by a broad array of biologically active chemistry. In vitro formation of storage organs requires months in the lab instead of years in the field, when water and nutrients are correctly supplied. Liquid and agar systems in large and small vessels were compared for sugar and water use with turmeric (Curcuma longa) as a model plant. Small jars on a shaker were compared with large, flat-bottomed vessels containing thin films of liquid media, intermittently tilted at slight inclines that allow the advantages of liquid phase transfer with gentle agitation. Liquid culture in small vessels on a shaker yielded the most plants and liquid culture on a thin-film rocker in a large vessel yielded the largest plants. Increased and improved biomass (fresh and dry) in liquid culture compared to agar was based on greater sugar use. When large vessels of liquid media were grown for 5 and 6 months on a rocker, 400 mL of media yielded 150 to 200 g (fresh weight) of plants. Similarly, 13 to 16 g (dry weight) of plant tissue was derived from 24 g of sugar. Plants were about one-third rhizome by fresh mass. Rhizomes had greater dry and fresh weight than leaves or roots, indicating solute actively accumulated in the rhizome. The rhizomes had normal morphology, characteristic pigments and fragrance, and rhizome extracts had strong antioxidant potential. The gentle rocking action of plantlets in sugar-containing liquid medium was demonstrated to produce functional storage organs.

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Franco Famiani and Robert P. Walker

in titratable acidity concomitant with a substantial increase in the content of soluble solids and anthocyanins ( Perkins-Veazie et al., 2000 ; Tosun et al., 2008 ; Walsh et al., 1983 ). The large increase in sugar content that occurs during

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Y. Hayata, Y. Niimi, K. Inoue, and S. Kondo

Solutions of CPPU and BA were applied to ovaries of melon (Cucumis melo) flowers with or without pollination, and the effects on fruit set, growth, and sugar content were investigated. Treatment with CPPU increased fruit set in both seeded and seedless melons. Even at low concentrations, CPPU had a strong effect on fruit set in the seeded melons. In seedless melons, CPPU induced 100% parthenocarpic fruit set when applied with 10 mg·L–1; lower concentrations were much less effective. Treatment with BA increased fruit set in seeded melons, but was not particularly effective in the absence of pollination. During the first 10 days after anthesis, CPPU promoted fruit growth, but between 8 and 13 days after anthesis, the growth rate was lower than in the controls. Treatment with CPPU had little effect upon soluble solids (SS) levels in seeded fruit. SS content was significantly lower in seedless than in seeded fruit; this difference was larger in the placenta than in the mesocarp. Sucrose levels of both seeded and seedless fruits were consistently higher than glucose and fructose levels. High concentrations of CPPU reduced sucrose levels in the placenta of seedless fruit. These results indicate that seeds play an important role in sugar accumulation and melon fruit growth during later stages of development. Chemical names used: [1-(2-chloro-4-pyridyl)-3-phenylurea] (CPPU); 6-benzylaminopurine (BA).

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Jonathan H. Crane, Pollyana Cardoso Chagas, and Edvan Alves Chagas

Sugar apple is a member of the Annonaceae, indigenous to the Caribbean Islands and lowlands of Central America ( Cordeiro, 2000 ; Pinto et al., 2005 ). The fruit is grown on a small scale throughout tropical and warm subtropical areas of the

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william M. Walter Jr.

The sugar content of the sweetpotato cultivars Centennial, Coroner, Georgia Red, Jewel, and Sweet Red was measured by nign performance liquid chromatography (HPLC) and compared to the sugar content found by measuring the refractive index of cellular sap and converting the refractive index value to sugar concentration. The sugar content and refractive index values were measured for just-harvested, cured and stored roots. Changes in the sugar content as determined by refractive index were found to be linearly related to changes 1n sugar content measured by HPLC, indicating that this method can be used to monitor changes in postharvest sugar content.

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S. Gamiely, W.M. Randle, H.A. Mills, D.A. Smittle, and G.I. Banna

Nitrogen applied as NH4-N or NO3-N (75 mg·liter-1) affected onion (AIlium cepa L.) plant growth when grown in solution culture. Nitrate alone or in combination with NH4-N increased leaf fresh and dry weight, leaf area, root fresh and dry weight, and bulb dry weight when compared to growth with NH4-N as the sole N source. Bulb fresh weight was highest with an NH4-N: NO3-N ratio between 1:3 and 3:1. Maximum leaf fresh weight was not necessary to produce maximum bulb fresh weight when onions were subjected to different N-form ratios. Precocious bulbing resulted when NH4-N was the sole N source; however, high bulbing ratios early in plant development were not correlated with final bulb fresh weight. Nitrogen form also influenced water uptake and pungency, as measured by enzymatically developed pyruvate concentration, but did not affect bulb sugar concentration.