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  • Author or Editor: D.G. Richardson x
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`D'Anjou' pear (Pyrus communis L.) trees were sprayed with zero or 32.3 mm CaCl2 during fruit development at 55, 86, 125, and 137 d from full bloom and harvested at 85% (immature), 100% (mature), and 110% (overmature) maturity stages. The fruit were stored in air at –1 °C for several periods to determine the effect of CaCl2 treatments on chilling requirement to accomplish ripening during 11 d at 20 °C. Immature or mature unsprayed fruit required 55 d, while the overmature fruit required 40 d at –1 °C to gain the capacity to produce ethylene during ripening at 20 °C. Calcium sprays increased flesh firmness at harvest by 15 N, fruit Ca concentrations by an average of 0.01 mg·g-1, fresh mass basis, and the chilling requirements by at least 15 d. Unsprayed immature fruit contained more Ca than the sprayed mature or overmature fruit, but their chilling requirement was similar. These results suggest that high Ca concentrations may increase the chilling requirement of `d'Anjou' pears in a developmentally related manner.

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To determine the ability of `d' Anjou' pear fruit to produce climacteric ethylene postharvest, fruit were harvested at a mature green stage, chilled at -1 °C for various times, then transferred to 20 °C to ripen. In addition, fruit were first held at 20 °C for various times, then at –1 °C for various durations, followed by transfer to 20 °C for 11 days. As storage time at –1 °C increased from 0 to 70 days, the time required to induce climacteric ethylene when transferred to 20 °C progressively decreased from 90 to 0 days. The total storage time (sum of d at chilling and nonchilling temperature) needed to induce climacteric ethylene remained nearly constant (70 to 90 days). However, this was not the case with fruit held initially at 20 °C, then transferred to –1 °C. The total storage time needed before the pears produced climacteric ethylene ranged from 70 to 110 days and increased with time of storage at 20 °C. These fruit required more time at –1 °C than those first stored at –1 °C. The chilling requirement mechanism of `d' Anjou' pears remains intact even during storage at nonchilling temperature and diminishes with senescence.

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Pear trees (Pyrus communis L.), cv. d'Anjou, received foliar applications of X-77 surfactant and 32.3 mm CaCl2 at 55, 85, 125, and 137 days after full bloom (DAFB) and fruit were harvested at 147 DAFB. Samples of fruit were stored in air either at 20 °C continuously or at 5 or 10 °C for several periods, then transferred to 20 °C, to determine the effects of storage temperature and CaCl2 treatments on the development of the ethylene climacteric and flesh firmness loss. Control fruits held continuously at 20 °C required 70 days for the onset of climacteric ethylene production, which commenced when firmness had decreased to ≈20 N. Calcium-sprayed fruit required 80 days at 20 °C before the rise in ethylene and resisted softening for ≈50 days. Regardless of calcium treatment, pears stored at 5 or 10 °C required only 40 days to produce climacteric ethylene; fruit softening and internal ethylene concentration after storage at 10 °C were intermediate between those of fruits stored at 5 and 20 °C. Calcium application did not alter the sequence of ripening events.

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Mature `Anjou' pears (Pyrus communis L.) continuously stored at 20 °C or -1 °C before transfer to 20 °C exhibited differences in the sequence of ripening events up to 100 days. Pears continuously held at 20 °C showed little change in ripening characteristics (chlorophyll, firmness, titratable acidity) for 14 to 28 days, then these characteristics decreased at a daily rate of 1.4% thereafter. A 40% increase in soluble polyuronides paralleled the firmness loss, while ACC did not exceed 0.5 nmol·g-1 until the 84th day, and internal ethylene did not exceed 0.2 μL·L-1 until after 90 days, whereas ACC oxidase activity (and total protein) peaked after 63 days. `Anjou' pears stored at -1 °C showed no changes in chlorophyll, firmness, protein, or total polyuronides for at least 84 d. Despite essentially no change in firmness during -1 °C storage, there was a slow but steady increase (≈15 %) in soluble polyuronides. ACC oxidase activity, expressed as ethylene production, rose to 71 nL·g-1·h-1 and the ACC content increased to almost 1.0 nmol·g-1 by the 84th day. Internal ethylene slowly increased and levelled to 1 μL·L-1 by the 56th day. Satisfaction of a chilling requirement thus appears to favor the development of ethylene synthesis capacity, which on transfer from cold storage to higher temperatures results in enough internal ethylene to rapidly drive the associated ripening mechanisms. Fruit for which the chilling requirement (≥70 days at -1 °C) was met softened in response to accelerated internal ethylene production on transfer to 20 °C for 7 days. However, pears that were not chilled or partially chilled did not sustain the increased ACC levels or ACC oxidase activity. Chemical name used: 1-aminocyclopropane-1-carboxylate (ACC).

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Abstract

Diurnal leaf and fruit water Potentials (Ψ) of sweet cherry (Prunus avium L.) showed that fruit pedicel Ψ was always lower at 6 AM then leaf Ψ but leaf Ψ as usually lower during the day. Varietal differences in Ψ occur but fruit maturity does not appear to have an effect. Minimum fruit pedicel Ψ was reached at about 2 PM and then recovered to the earlier higher Ψ as water uptake occured during the night.

Open Access

Abstract

A technique is described whereby osmotic potential, turgor potential and total fruit water potential can be determined quickly in the field with the aid of a pressure bomb, a hand held refractometer, and a percent soluble solids to osmotic potential conversion chart. A unique inverse linear relationship between percent soluble solids and osmotic potential was found for each fruit species. Application of this technique to rain cracking of ‘Napoleon’ sweet cherries (Prunus avium L.) shows that cracking is not strictly related to percent soluble solids, osmotic, turgor, or fruit water potential. This suggests that the degree of cuticular permeability, cuticular strength, cell wall strength or other factors may be of greater importance in determining cracking susceptibility than water potential parameters.

Open Access

Abstract

Chlorogenic acid and arbutin reduced spore germination of Penicillium expansum Lk. ex Thom, and mycelial growth of Mucor piriformis Fischer. Arbutin decreased growth of Botrytis cinerea Per ex Fr. However, chlorogenic acid increased both germination and growth of B. cinerea.

Open Access

Abstract

Alfalfa greening, (green stain, green mottle, or superficial cork) is a physiological disorder of ‘Anjou’ pear fruit, Pyrus communis L. This disorder is characterized by green streaks, blotches, and specks on the skin occurring most frequently at the stem end; it may also extend to the calyx end where superficial cork is also frequently present. Mineral analysis of the peel and whole fruit of alfalfa greening-affected fruit indicated that the disorder was associated with higher nitrogen, potassium, and phosphorus content but lower calcium levels than normal fruit.

Open Access

Abstract

Several compounds were used to desiccate tops of onion (Allium cepa L.) prior to harvest. Most chemicals at various rates and timings caused an increase in postharvest disease and sprouting. Endothall at 1.1 kg active ingredient/ha had storage losses comparable to the control. Paraquat substantially elevated storage decay at all rates, but there was less increase from Ethephon and Stoddard Solvent. Disease in storage was not correlated with neck moisture as affected by spray treatments. Phenolic concentration in neck tissue studied for several treatments was weakly and negatively correlated with subsequent disease in storage.

Open Access

Abstract

Fruit quality of ‘Starkspur Golden Delicious’ apples (Malus domestica Borkh.) on 6 rootstocks [Seedling, Mailing (M) 1, M ailing Merton (MM) 106, M 7, OAR 1, M 26] grown in a high density orchard at 2 levels each of K and N was studied at 3 harvest dates and after 6 months of 0°C storage from 1980 to 1982. Fruit on OAR 1 rootstock had greater soluble solids, more yellow color at harvest and after storage and were relatively firmer at harvest, but were smaller than those from other rootstocks. Fruit on M 7 had lower soluble solids than most of the other rootstocks at harvest time. Fruit from MM 106 had a lower incidence of breakdown in storage than most others. Crop load influenced both harvest and storage quality. Fruit on M 26, which had a light crop in 1981, were larger, yellower, and had higher soluble solids, and also had more storage breakdown (about 20%) and bitterpit (about 12%) than other rootstocks. Rootstocks or fertilizers did not affect fruit respiration. Little effect of K fertilizer was found on any quality indices, whereas high N treatments produced greener fruit than did low N.

Open Access