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Sandra B. Wilson, Jeongwook Heo, Chieri Kubota, and Toyoki Kozai

Sweetpotato [Ipomoea batatas (L.) Lam., `Beniazuma'] plantlets were grown photoautotrophically (without sugar) for 12 days in an improved forced ventilation system designed with air distribution pipes for uniform spatial distributions of carbon dioxide (CO2) concentration. Enriched CO2 conditions and photosynthetic photon flux (PPF) were provided at 1500 μmol·mol-1 and 150 μmol·m-2·s-1, respectively. The forced (F) ventilation treatments were designated high (FH), medium (FM), and low (FL), corresponding to ventilation rates of 23 mL·s-1 (1.40 inch3/s), 17 mL·s-1 (1.04 inch3/s), and 10 mL·s-1 (0.61 inch3/s), respectively, on day 12. The natural (N) ventilation treatment was extremely low (NE) at 0.4 mL·s-1 (0.02 inch3/s), relative to the forced ventilation treatments. Total soluble sugar (TSS) and starch content were determined on day 12. Total soluble sugars (sucrose, glucose, fructose) of FH plantlets were lowest in leaf tissue and highest in stem tissue as compared to other ventilation treatments. Starch concentration was higher in leaf tissue of FH or FM plantlets as compared to that of FL or NE plantlets. Plantlets subjected to FH or FM treatments exhibited significantly higher net photosynthetic rates (NPR) than those of the other treatments; and on day 12, NPR was almost five times higher in the FH or FM treatment than the FL or NE treatments. Carbohydrate concentration of plantlets was also influenced by the position of the plantlets in the vessel. Within the forced ventilation vessels, leaf TSS of FH and FM plantlets was similar regardless of whether plantlets were located near the inlet or outlet of CO2 enriched air. However, under FH or FM conditions, leaf starch concentration was higher in plantlets located closest to the CO2 inlet as compared to the outlet.

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Yosef Burger, Uzi Saar, Nurit Katzir, Harry S. Paris, Yelena Yeselson, Ilan Levin, and Arthur A. Schaffer

Fruit sweetness is the major determinant of fruit quality in melons (Cucumis melo L.) and reflects the concentration of the three major soluble sugars, sucrose, glucose, and fructose, present in the fruit flesh. Of these three sugars, sucrose is the prime factor accounting for both the genetic and the environmental variability observed in sugar content of C. melo fruit. Faqqous (subsp. melo var. flexuosus), a cultivar having a low sucrose and total sugar content, was crossed with Noy Yizre'el (subsp. melo var. reticulatus), a cultivar having a high sucrose and total sugar content. F1 plants had a sucrose content averaging slightly higher than that of the low-sucrose parent, indicating that low sucrose content is nearly completely dominant. Segregation in the F2 and backcross progenies indicated that high sucrose accumulation in melon fruit flesh is conferred by a single recessive gene herein designated suc. When the high-sucrose parent was crossed with the moderate-sucrose landrace known as Persia 202 (subsp. melo var. reticulatus), the segregation in the filial and backcross progenies suggested that additional genetic factors affect the amount of sucrose accumulation.

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Rafael Alique, José P. Zamorano, Ma Luisa Calvo, Carmen Merodio, and José L. De la Plaza

`Fino de Jete' cherimoya fruit were stored at 20, 10, 8, or 6C, 80% relative humidity. Two rises of CO2 production and an ethylene rise following the first peak of respiration were obtained in fruit held at 20C. The ripe stage coincided with the onset of the second respiratory rise. Soluble sugar and organic acid concentration were maximal, and flesh firmness was 18 N in ripe fruit. Lower temperature reduced respiration rate and ethylene production; however, some stimulation of ethylene synthesis was observed at 10C. Cherimoyas ripened to edible condition during 6 days at 10C, but fruit maintained at 8C for up to 12 days required transfer to 20C to ripen properly. Our results suggest that high increases in CO2 are not sufficient to complete cherimoya fruit ripening without the concurrent rise in ethylene production. Citric acid accumulation, inhibition of ethylene synthesis, and reduced accumulation of sucrose were observed during storage at 6C. Removal to 20C after 12 days at 6C resulted in no ripening, almost complete inhibition of ethylene synthesis, and severe skin browning. Thus, 8C is the lowest tolerable temperature for prolonged cold storage of cherimoya `Fino de Jete'. Fruit can be held at 8C for up to 12 days without damage from chilling injury.

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Annick Moing, Christel Renaud, Monique Gaudillère, Philippe Raymond, Philippe Roudeillac, and Béatrice Denoyes-Rothan

As genetic factors affect strawberry (Fragaria ×ananassa Duch.) fruit development and quality, changes in metabolite concentrations were studied during fruit development of four strawberry cultivars grown in the field: three commercial cultivars (Capitola, Elsanta and Dover) and a genotype from Centre Interrégional de Recherche et d'Expérimentation de la Fraise, France (`CF1116'). Major and minor metabolites changed with development. The two strawberry cultivars with the highest starch content at early stages, `Capitola' and `Elsanta', also had the highest fruit weight at harvest. There was no correlation between strawberry weight and osmolarity. At maturity, significant differences were observed among cultivars for most of the metabolites studied. `Capitola' and `Elsanta' responded similarly for most measured variables. `CF1116' was characterized by high juice osmolarity and high sucrose, inositol, glutamine, arginine and alanine concentrations, and low citrate and malate concentrations. `Dover' was characterized by a high galactose concentration and low asparagine and alanine concentrations. Organic acid differences among cultivars appeared early during development, while differences in soluble sugars appeared during maturation. The developmental pattern of each amino acid varied among cultivars. Timing of the biochemical differences observed among cultivars provides some information on their metabolic origin.

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Avinoam Nerd and Yosef Mizrahi

Changes occurring during fruit ripening and duration of fruit development were studied in Selenicereus megalanthus (Scum. ex Vaupel) Moran (yellow pitaya), a climbing cactus grown in protected structures at three sites in the Israeli Negev desert. During ripening, peel color turned from green to yellow, fruit dimensions slightly changed, and pulp content markedly increased. Total soluble solids and soluble sugars in the pulp increased, while starch content decreased. Acidity decreased at the last stage of ripening. Fruit in which most of the peel area had turned yellow (stage 4) were given the highest taste grade by a panel of tasters. Measurements of ethylene and CO2 evolution indicated that fruit was nonclimacteric. The mean number of days from anthesis to fruit of stage 4 was negatively correlated with the mean of the maximum and the minimum temperatures during the growth period. Daily accumulation of heat units (HUs) was calculated as the difference between daily mean temperature and a base temperature of 7 °C. Sum of HUs for the period from anthesis to ripening was 1558±12 HUs.

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Christopher M. Menzel and Lindsay Smith

substances such as starch (storage sugar) and soluble sugars, which do not form part of the cell structures such as the cell wall ( Da Silveira et al., 1978 ). These carbohydrates are then available for cell metabolism, whereas carbohydrates in the cell wall

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Rafael Urrea-López, Rocío I. Díaz de la Garza, and Juan I. Valiente-Banuet

caused a significant increase in fruit glucose levels. Accordingly, in ‘Caballero’ peppers, a 20% increase in soluble sugars was observed in fruit grown at high salinity levels ( Azuma et al., 2010 ). Salinity in soil can be responsible for changes in

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Alexandra Boini, Enrico Muzzi, Aude Tixier, Maciej Zwieniecki, Luigi Manfrini, and Luca Corelli Grappadelli

growth resumption and development of new organs, such as flowers and leaves, in spring. Hence, before and during breaking of dormancy, conversion of nonsoluble to soluble sugars takes place ( Charrier et al., 2013 ; Hartmann and Trumbore, 2016 ; Tixier

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A.M. Salama, J.R. Hicks, and J.F. Nock

Maleic hydrazide (MH)-treated and untreated (control) onion (Allium cepa L.) bulbs were stored for up to 20 weeks at 0, 15, or 30C with relative humidities (RH) of 40% or 60%. MH and RH had minimal effect on sugars and organic acids in inner or outer scale leaves that were analyzed at S-week intervals. Concentrations of fructose, glucose, and total sugars were higher in inner than outer leaves of the bulb, while the reverse was true for sucrose. Total sugars, glucose, and fructose decreased and sucrose increased with higher storage temperature. Total sugars and glucose decreased with increased storage duration. Malic acid concentration was greater in the outer leaves while citric acid levels were higher in inner leaves. Malic acid increased in onion bulbs during storage while citric acid levels were not influenced by storage duration. Total acids showed little difference across temperatures, due to the concurrent increase in citric acid and decrease in malic acid at 30C.

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Nanqing Liu, Yixin Shen, and Bingru Huang

were frozen in liquid nitrogen for the analysis of content of major osmoregulants, including soluble sugars, proline, PAs [putrescine (Put), spermidine (Spd), and spermine (Spm)], and GB. Soluble sugars were determined using the phenol–sulfuric acid