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M. Hossein Behboudian and Colin Tod

The effect of preharvest CO2 enrichment (1000 μl·liter–1) on postharvest quality of tomato fruit (Lycopersicon esculentum Mill. `Virosa') was studied with an emphasis on soluble sugars, ripening, and mineral composition. High-CO2 fruit had higher concentrations of sucrose, glucose, fructose, and total soluble solids than ambient-CO2 fruit. High-CO2 fruit also ripened more slowly and was characterized by lower respiration and ethylene production rates than ambient-CO2 fruit. Concentrations of N, P, and K were lower in the high-CO2 fruit than in the ambient-CO2 fruit, whereas those of S, Ca, and Mg were the same for both treatments. Preharvest CO2 enrichment of `Virosa' tomato enhances fruit desirability in terms of slower postharvest ripening and higher concentrations of soluble sugars and total soluble solids.

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J. Lopez, L.E. Parent, N. Tremblay and A. Gosselin

In hydroponic recirculating systems, sulfate ions can accumulate to excessive levels and interfere with other nutrient ions. The objective of this research was to determine the effects of four sulfate concentrations on growth and mineral nutrition of greenhouse tomato plants (Lycopersicon esculentum Mill. cv. Trust). Tomato seeds were sown in flats and subsequently transplanted into rockwool slabs. Ten days after transplanting, plants were given four sulfate concentrations in nutrient solutions (S0 = 0.1, S1 = 5.2, S2 = 10.4, and S4 = 20.8 mM). The plots were arranged in a randomized complete-block design with four replications. Treatment S0 reduced dry weight of the top portion of the plant. A sulfate shortage in the nutrient solution decreased S concentrations in the leaf and decreased fruit number. Activities and concentrations of major ions in solutions expressed in mM or as row-centered logratios were correlated with corresponding foliar concentrations expressed in grams of nutrient per kilogram of dry matter or as row-centered logratios. Data were presented in this manner in order to explore interactive models describing relationships between mineral composition of both nutrient solutions and plant tissues. High concentrations of sulfate ions in the nutrient solution up to 20.8 mM did not affect tomato growth or yield. Tomato plants appeared prone to sulfate deficiency, but tolerant to sulfate concentrations up to 20.8 mM in the nutrient solution.

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C.O. Chardonnet, C.E. Sams and W.S. Conway

`Golden Delicious' apples (Malus ×domestica Borkh.) were pressure-infiltrated after harvest with 0%, 1%, 2%, 3%, or 4% CaCl2 solutions (w/v) and the chemical composition of the cell wall of the cortical tissue 2 to 4 mm under the epidermis was studied. The mineral composition of the control cell wall (0% CaCl2) was not affected by the pressure infiltration process. In addition, no significant change was noticed in cell wall associated protein, uronic acid, total polysaccharides, or non-cellulosic neutral sugar contents except for xylose and rhamnose, which decreased (-25%) and increased (+20%), respectively. When apples were infiltrated with CaCl2, Ca content of the cell wall increased and maximum accumulation was achieved with a 2% CaCl2 solution. Calcium infiltration also induced a two-fold increase in Na, a 27% decrease in P, and a 40% decrease in protein content. These data suggest that chemical changes occurring after Ca infiltration are not related to pressure infiltration alone, but are mainly due to the Ca accumulation in the cell wall after pressure infiltration of CaCl2 solutions. Saturation of the available binding sites for Ca occurred in the cell wall when fruit were infiltrated with 2% CaCl2, as no further significant changes in the cell wall chemical composition was detected in fruits infiltrated with 3% or 4% CaCl2.

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W. Mark Kliewer and Jason Benz

The effects of 7 rootstocks (AxR#1, 110R. 5C, 3309, 420A, 1616 and 039-16) grafted to Cabernet Sauvignon (clone #8) in combination with 3 between row spacings (2, 3, and 4 m) and 2 in-row spacings (1 and 2 m) on the level of minerals in petioles sampled at full bloom and at veraison on the mineral composition of fruits at harvest were evaluated over a 3 year period (1991 to 1993) in a replicated field plot established at Oakville in 1987. 039-16 petioles had the highest level of K, Ca and NO3, whereas 420A had the lowest concentration of these minerals, the other 5 stocks being intermediate. Petiole Mg level was highest in 420A and lowest in 039-16. 039-16 fruits at harvest had the highest level of K, malate, and pH, whereas 420A fruits were lowest in these substances. Between row spacing showed no significant effects on the concentration of minerals in leaves and fruits. However, leaves from vines spaced 1 m apart within rows had lower levels of Ca and Mg than 2 m vine spacing. One m vine spaced fruits were lower in °Brix hut higher in titratable acidity and malate than 2 m vine spaced fruits. Regression analysis showed that the number of roots per unit volume of soil was positively related to the concentration of K in leaves and fruits, regardless of the rootstock used.

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Mustafa Ozgen, Artemio Z. Tulio Jr., Aparna Gazula, Joseph C. Scheerens, R. Neil Reese, A. Raymond Miller, Shawn R. Wright, Brent L. Black and Ingrid M. Fordham

Autumnberry (Elaeagnus umbellata, “A”) and cornelian cherry (Cornusmas, “CC”) genotypes were examined for mineral composition, anthocyanin, phenolic and tannin contents, antioxidant characteristics and levels of individual phenolic compounds via GC-MS. Values were compared with those of 58 cultivars of blackberries (“B”), black raspberries (“BR”), cranberries (“C”), elderberries (“E”), grapes (“G”), red raspberries (“RR”) and strawberries (“S”). The phenolic content of “CC” (6955 μg·gfw-1) was greater than 2× that of “B”, “BR” and “E”. Phenolic contents of “A” samples (1058-1776 μg·gfw-1) were similar to those of “RR”, red “G” and “S”. Anthocyanin levels in “CC” (270 μg·gfw-1) resembled those in “C”. “A” did not contain anthocyanins. Fruit of “CC” and “A” possessed high tannin levels (9291 μg·gfw-1 and 1410–5403 μg·gfw-1, respectively) and exhibited high antioxidant potential (μmol·gfw-1 trolox equiv.). DPPH and FRAP values of “CC” (72.1 and 94.9, respectively) were greater than 2× those of “BR”. DPPH values of “A” (23.9–56.2) were ≥ values for “BR”, whereas “A” FRAP values (13.3–34.0) were similar to those of “B” and “RR”. However, the lipid-soluble antioxidant potential of lycopene-rich “A” was substantial. Levels of individual compounds varied among cultivars. Ca and Mg contents of “A” were less than those found in “CC” and “BR”. Other mineral levels were comparable.

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Waylen Y. Wan, Weixing Cao and Theodore W. Tibbitts

Because tuberization in potatoes (Solarium tuberosum L.) reportedly is inhibited when stolons are immersed in liquid, this study was conducted to determine the effect of intermittent pH reductions of the nutrient solution on tuber induction of potatoes in solution culture. Tissue-culture potato plantlets were transplanted into solutions maintained at pH 5.5. The pH of the nutrient solution was changed to 3.5 and 4.0 for 10 hours on each of three dates (30, 35, and 40 days after transplanting). For the pH 3.5 treatment, tubers were observed first on day 42 and averaged 140 tubers per plant at harvest on day 54. For the pH 4.0 treatment, tubers were observed first on day 48 and averaged 40 tubers per plant at harvest. At a constant pH 5.5, tubers were observed on day 52 and averaged two tubers per plant at harvest. Plants with the intermittent pH 3.5 had smaller shoots and roots with shorter and thicker stolons compared to constant pH 5.5. With the intermittent pH 4.0, plants were of similar size, but stolons were shorter and slightly thickener compared to those from pH 5.5. Mineral composition of leaf tissues at harvest was similar for the three pH treatments. These results indicate that regulation of solution pH can be a useful technique for inducing tuberization in potatoes.

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Driss Iraqi, Serge Gagnon, Sylvain Dubé and André Gosselin

Tomato production represents >70% of all greenhouse vegetables produced in Quebec, Canada. To obtain high yields and high quality fruit, an adequate control of greenhouse environmental characteristics, including the vapor pressure deficit (VPD), is necessary. Our study examines four VPD treatments (0.5 kPa day and night, 0.8 kPa day and night, 0.8 kPa day 0.5 kPa night, and automatic VPD management according to transpiration) and three photoperiods [12 h, 14 h, and variable-12 h (summer) 16 h (winter)] on growth, yield, and photosynthetic capacity of tomato plants. Greenhouse temperature was maintained at 22C day/18C night. Pure CO2 was injected into the greenhouse to maintain a constant atmospheric concentration of 800 ppm throughout the experiment. Growth, yield, and leaf mineral composition were determined monthly for each treatment during the experiment. The photosynthetic rate of the 5th and 10th leaves also were measured in addition to the content of chlorophyll a and b. Our results indicated an increase in total yield and photosynthetic rate under a VPD of 0.8 kPa during day and night. An increase in leaf mineral concentration also was noted in plants grown under high VPD. Differences in yield and photosynthetic capacity were not found between the three photoperiods studied. However, there was a tendency to have higher yields under longer photoperiods.

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Usman Siswanto and Frank B. Matta

This study was established to determine the influence of scion/stock combination on leaf area, yield efficiency, and fruit quality attributes in effort to identify the most suitable scion/stock combination for Mississippi. Twenty-nine scion/stock combinations were grown at the Pontotoc Ridge-Flatwoods Research and Extension Center, North Mississippi. The treatments were arranged in a completely randomized design (CRD) with six single tree replications. `Jon-A-Red' on Mark produced the smallest leaf area, while the largest leaf area was produced by the combination of `Royal Gala' on MM106 and `Blushing Golden' on M7A. Scion/stock combinations significantly affected yield efficiency, fruit yellow pigment dvelopment, firmness and fruit mineral composition. Scion cultivars on Mark resulted in the highest yield efficiency, except `Empire'. `Ultra Gold' and `Braeburn' on Mark and `Blushing Golden' on MM111 led to yellow pigmentation in the highest category. Meanwhile, `Braeburn' on Mark was among the scion/stock combinations that produced the firmest fruit. And fruit from trees on Mark consistently had high calcium (Ca) levels. After 7 years, `Royal Gala' on Mark produced the highest yield efficiency. `Braeburn' on Mark resulted in both the firmest fruit and the highest fruit Ca concentration.

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Mongi Zekri and Robert C.J. Koo

Controlled-release sources of N and K were compared with soluble sources on young `Valencia' orange trees (Citrus sinensis [L.] Osb.). The effects of these fertilizers on leaf mineral concentration, soil chemical analysis, and tree growth were evaluated for 3 years. Soluble fertilizers were generally more readily available but had shorter residual effects on leaves and soil than controlled-release fertilizers. In the top 30 cm of soil, the plots treated with controlled-release N had 23% more total N than those treated with soluble N sources, while the plots fertilized with controlled-release K contained 56% more extractable K than those that received soluble K. Different effects on leaf and soil N between the two controlled-release N sources, sulfur-coated urea (SCU) and methylene urea (MU), were also found. With the use of controlled-release fertilizers, application frequency was reduced from a total of 15 to six applications with no adverse effects on tree growth, leaf mineral composition, or soil fertility during the first 3 years. Combining soluble and controlled-release fertilizers in a plant nutrition program offers an economical and effective strategy for citrus growers.

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Alireza Talaie*, Alireza Esmaili Falak and Mohammad Ali Asgari

The main aim of this study was to investigate the effects of two apple rootstocks (M9 and Seedling) on the growth, total yield, fruit quality and mineral composition in leaves and fruits of two Iranian cultivars Golab Kohanz and Shafiabadi. The 10-year-old experimented trees were on stage of commercial cropping. The experiment was conducted in a randomized complete-block design in split plot tests with two factors and four replications.The effects of rootstocks on trunk diameter, current seasonal shoot length, primary fruit set percentage, total yield/ha and individual fruit weight were significant (P < 0.01) in first year, but not significant on total yield and individual fruit weight in the second year. The effect of cultivar was only significant at current seasonal shoot length in the first year and total yield and individual fruit weight in both years. Fruit characters were also affected by rootstock, so fruit on M9 rootstock had more flesh firmness, most PH, TSS, and dry matter, but the effect of cultivars was not significant on fruit quality characters in both years. Cultivar Shafiabadi on M9 rootstock produced the highest yield/ha in all treatment combinations. The results of mineral analysis relieved the effects of rootstock on N and Zn concentration in leaves. Golab Kohanz/M9 rootstock showed the highest K content in leaves while the highest Zn amount was Golab Kohanz/Seedling rootstock. Other nutrient contents were affected neither by rootstocks nor cultivars. In fruit, rootstock effect on Mg and P concentration was significant; and the highest K content was found in fruit of Golab Kohanz/M9 and the highest Mg and Ca amount was also recorded in Golab Kohamz/Seedling rootstock.