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Yosef Al Shoffe, Abdul Sattar Shah, Jacqueline F. Nock, and Christopher B. Watkins

‘Honeycrisp’ apples are susceptible to the physiological disorder soft scald, especially when stored at temperatures close to 0 °C. The disorder can be reduced by a conditioning treatment of 10 °C for 7 days before storage, but little is known about the underlying physiology of disorder development. The effects of storing ‘Honeycrisp’ apples in air at 0.5 °C for a total of 140 days, without and with conditioning, on internal ethylene concentration (IEC), ethanol and acetaldehyde concentrations, and activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) were investigated in relation to soft scald incidence. Fruit were selected on the basis of background color (chlorophyll concentration) using a nondestructive delta absorbance (DA) meter to minimize variability of fruit maturation. Conditioning reduced soft scald incidence to 1% compared with 28% in unconditioned fruit. During the conditioning period, IECs were usually greatest in the conditioned fruit, with no effect on ethanol and acetaldehyde concentrations. During subsequent storage, IEC was greatest in conditioned fruit, whereas ethanol and acetaldehyde concentrations were generally less. However, ADH and PDC activities were unaffected consistently by conditioning or during storage.

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Eric J. Hanson and G. Stanley Howell

Mature `Concord' vines (Vitis labrusca L.) were excavated at 2- to 4-week intervals through the season to study seasonal changes in vine N concentration. Vine N content began increasing 2 weeks after budbreak, increased most rapidly from mid-May to mid-July, and declined between fruit maturation and the beginning of leaf senescence. Vine N content was lowest at budbreak (18 g) and maximum at fruit maturity (75 g). This change represented a net accumulation of 57 g N/vine or 77 kg N/ha. In a separate study, `Seyval blanc' vines were treated with double 15N-labeled ammonium nitrate at either budbreak or bloom. Labeled N was applied as a spray beneath vines to simulate a broadcast vineyard application. Vines were excavated when leaves began to senesce in October, partitioned into various components, and analyzed by mass spectrophotometry to determine fertilizer-derived N content. Vines had recovered statistically similar percentages of fertilizer N applied at budbreak (7.1%) and bloom (10.6%). The low recovery of fertilizer N likely resulted from the method of fertilizer application, the presence of a competitive grass sod between the rows, and relatively high native soil N levels.

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Floyd M. Woods*, William A. Dozier Jr., Robert C. Ebel, David G. Himelrick, Cecilia Mosjidis, Raymond H. Thomas, Bryan S. Wilkins, and James A. Pitts

The relationship between fruit maturation and accumulation of hydrogen peroxide (H2 O2), lipid peroxidation, ethylene (C2 H4) production, antioxidant activity (hydrophilic, lipophilic and total) and the antioxidant enzyme ascorbate peroxidase (APX, EC 1.11.1.11) in fruit pericarp tissue of `Chandler' (Fragaria × ananassa Duch.) strawberry were measured. `Chandler' fruit pericarp maturation and ripening were accompanied by a decline in H2 O2 content early in fruit development followed by a rapid accumulation. An increase in membrane lipid peroxidation (thiobarbituric acid reactive substances, TBARS) coincided with accumulation of H2 O2, which preceded a rise in C2 H4 production. In general, antioxidant activity declined as fruit matured and ripened. APX enzyme activity increased by 2-fold and peaked at the pink stage of development and then gradually declined with ripening. H2 O2 may serve as a signal molecule to initiate the cascade of oxidative processes during maturation and ripening. APX enzyme activity during maturation and ripening was not substantial and thus, may not have a role in alleviating accumulation of H2 O2 and subsequent events related to oxidative senescence in fruit pericarp. To our knowledge, this is the first study to present fractionated antioxidant activities (HAA, LAA and TAA) from strawberry pericarp as assessed by the ABTS∼+ radical cation assay. A fundamental understanding of the mechanisms involved in the senescent related-oxidative changes during strawberry fruit ontogeny in relation to quality and nutrition is discussed.

Free access

Chao Gao, Rui Yang, and Deyi Yuan

Camellia oleifera is an important woody edible oil plant in southern China. In this study, the developmental differences in ovules at different positions in the ovary of C. oleifera were observed. The developmental type and characteristics of aborted ovules, ratios of normal and aborted ovules, and their developmental differences after flowering were examined. Ovules near the stylar end and in the middle exhibit normal development and are able to form embryo sacs; lower ovules near the pedicel end are usually aborted. The proportion of abortion of four examined cultivars ranges from 10.2% to 33.3%. Aborted ovules can be divided into four categories: 1) nascent egg apparatus lacking distinguishable cells; 2) completely absent egg apparatus structure consisting of flocculent tissue; 3) lack of tissue, comprising only integument cells; and 4) the inner integument not constituting a micropyle channel, with incomplete egg apparatus development and generating abnormal ovules. At 120 days after pollination (DAP), significant distinguishable size differences were found between fertile and aborted ovules; aborted ovules ceased growth at 180 DAP. On fruit maturation, aborted seeds were still attached to the placenta.

Free access

Huicong Wang and Lailiang Cheng

Apple maturity is often assessed by starch hydrolysis index, skin color, soluble solids, flesh firmness, and the rate of ethylene evolution. In red-fruited apple cultivars, the intensity and extent of coloration is an important consideration in determining the time of fruit harvest. Negative relationships have been found between tree nitrogen (N) status and fruit skin pigmentation, but how N affects flesh starch breakdown has not been examined in detail. The objective of this study was to determine how N supply affects flesh starch breakdown relative to skin color development. Seven-year-old ‘Gala’/M.26 trees were provided with four levels of N (8.8, 26.4, 52.7, and 105.4 g N per tree) in a modified Hoagland's solution. The effects of N supply on yield, fruit quality, and fruit maturation were evaluated. At harvest, fruit in the lowest N treatment was significantly smaller and had lower soluble solids but higher starch concentration, better color, and higher firmness than those grown at higher N supplies. Increasing N supply decreased both anthocyanin synthesis and chlorophyll degradation in fruit skin. Flesh starch concentration was higher at higher N supply at 38 days before harvest but was lower at higher N supply at harvest. Starch degradation was completed earlier during cold storage with increasing N supply. These results indicate that increasing N supply delays skin red color development but accelerates flesh starch degradation in ‘Gala’ apples. These differential effects of N supply should be taken into account when assessing fruit maturity for optimizing harvest time.

Open access

Haim Nerson, Ron Cohen, Menahem Edelstein, and Yosef Burger

Abstract

The effects of paclobutrazol (cultar, PP333) on yield and fruit quality of muskmelon (Cucumis melo L. var. reticulatus Naud. cv. Galia) were examined in a series of field experiments, in the spring at Newe Ya’ar (northern Israel) and in autumn at Biq’at HaYarden (lower Jordan Valley, eastern Israel). In the spring experiments, paclobutrazol applied at 2 and 4 mg·liter−1 as a drench to the media-mix of muskmelon transplants increased total fruit yield 15% to 20% at various plant populations and in combination with ethephon and/or chlorflurenol, but tended to decrease the early yield. Yield increase was due to an increase in fruit weight rather than number. Paclobutrazol, in general, tended to improve marketable yield, yield concentration, and netting index. In the autumn experiment, paclobutrazol was applied at 250 mg·liter−1 as a spray from flowering through fruit maturation and compared with benzyladenine (BA), and N, P, and K fertilization. Paclobutrazol reduced early leaf-yellowing symptoms, but was not as effective as BA. Paclobutrazol in the autumn experiment did not affect yield or yield components, but soluble solids content was significantly increased and keeping-quality was unaffected. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-l ethanol (paclobutrazol); (2-chloroethyl)phosphonic acid (ethephon); (methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate) (chlorflurenol); benzyladenine (BA).

Open access

Avinoam Golomb and Eliezer E. Goldschmidt

Abstract

Two alternate-bearing ‘Wilking’ mandarin (Citrus reticulata Blanco) trees, an “on” and an “off” tree, were uprooted and dissected into 11 organ types during the time of fruit maturation (February). Total or water-soluble N, P, K, Ca, and Mg (nitrate for soluble N) content were determined for each organ. Calcium was separated further into water-soluble, exchangeable, insoluble, and oxalate fractions. Leaves and twigs of on trees had reduced N, P, and particularly K levels. Organs of on trees, including minor roots and fruit, contained increased nitrate levels. Leaves, twigs, and minor roots of on trees accumulated Ca, mainly as Ca oxalate. The amounts of N, P, and K present in the fruit represented 32.2%, 43.7%, and 57.8%, respectively, of the total for an on tree. Fruit were very low in Ca, containing only 6% of the tree total. A 15-month follow-up of seasonal fluctuations in minerals of on and off ‘Wilking’ trees showed that the mineral composition of leaves and twigs was rapidly changed by the presence or absence of fruit. Defruiting in July prevented mineral depletion and permitted reasonable flower-bud differentiation on subsequent year. Leaf disks of on trees had low initial nitrate–reductase activity but responded weakly to nitrate induction. Leaves of overloaded on trees appear to suffer from a metabolic disorder involving relatively high nitrate levels, Ca accumulation, and loss of the nitrate–reductase induction response.

Open access

Anita Nina Miller, Beth Allyn Krizek, and Christopher S. Walsh

Abstract

The rate of ethylene evolution of peach fruit (Prunus persica L. Batsch) and ACC content of peach pericarp/mesocarp and seeds was determined during development. Ethylene measurements of whole fruit began 18 days after anthesis (DAA), and ACC quantification was started 32 DAA. ACC levels and ethylene evolution followed similar patterns during stages I and II of fruit growth. At 39 DAA, there was an increase in ethylene evolution and extractable ACC concentration of both pericarp and seeds; however, variability was high at this time. Ethylene evolved by nondeveloping fruit of the “second wave” and “June drop” increased after senescence of the ovule was observed. By 49 DAA, ethylene production and ACC concentration reached a minimum that lasted until a 10-fold increase in ethylene evolution was detected in late stage III. This 10-fold increase in ethylene occurred in four different peach cultivars sampled at “firm-ripe” stage. Seeds excised at 67 DAA, which were incubated for 6 hr in ambient O2 conditions, evolved 400 nl·g−1·hr−1 ethylene and ACC concentration averaged 54 nmol·g−1 fresh weight. It is suggested that in split-pit fruits, ethylene generated by the seeds may accelerate fruit maturation and ripening. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

Open access

T. J. Facteau

Abstract

Foliar applications of gibberellic acid (GA3) to mature ‘Lambert’ sweet cherry trees (Prunus avium L.) about 21 days before harvest increased fruit weight (fresh and dry), soluble solids (SS), alcohol-insoluble substances (AIS) (both concentration and per fruit), ash weight, and fruit firmness at harvest. Application of GA3 did not affect concentrations of ethylene diamine-tetraacetic acid (EDTA) or pectinase-soluble pectins and fruit Ca. GA3-treated fruit had lower concentrations of water-soluble pectins and reduced surface pitting. Fruits sampled at 3–7 day intervals (starting about 21 days before harvest) from control and GA3-treated trees showed that as an average response over a 29-day sampling period GA3 increased fruit weight, firmness, AIS concentration, AIS per fruit, pectinase-soluble pectins, and decreased water-soluble pectins. Neither total, residual, or soluble fruit Ca were affected by treatment with GA3. Fruit Ca levels remained constant, on a per fruit basis, during the last 3 weeks of fruit maturation but Ca concentration, expressed as fresh or dry weight, decreased as a result of increased fresh and dry weight. Higher Ca levels were not associated with firmer fruit (comparing GA3 and nontreated fruit), but were correlated positively with firmness in nontreated fruit.

Open access

G. Nir, I. Klein, S. Lavee, G. Spieler, and U. Barak

Abstract

The effect of evaporative cooling on budbreak and yield of Vitis vinifera L. (‘Perlette’ and ‘Thompson Seedless’) vines grown in the southern Jordan Valley in Israel was investigated. Overhead microsprinklers were operated from 0600 to 1800 hr daily during the autumn and winter months, either alone or in combination with cyanamide sprays after pruning. Evaporative cooling decreased the temperature of buds exposed to direct sunlight from 30° to 16°C and that of shaded buds from 25° to 13°. Evaporative cooling induced an early uniform budbreak. However, when evaporative cooling was combined with cyanamide spray, its effect was evident only during the initial phase of bud emergence. In 1985 cyanamide spray and evaporative cooling alone increased yield of ‘Perlette’ by 6% and 6% to 24%, respectively, and by 17% to 46% when both treatments were combined. In 1986 prolonged evaporative cooling increased the yield of ‘Perlette’ by 25% but, in combination with cyanamide, by only 11.6% over the unwetted cyanamide-treated control. In both years, evaporative cooling with or without cyanamide advanced fruit maturation.