Search Results

You are looking at 1 - 10 of 16 items for

  • Author or Editor: David R. Dilley x
Clear All Modify Search
Author:

Abstract

Ripening is the process by which physiologically mature fruits are transformed from a relatively unfavorable to a favorable condition with respect to texture, color, flavor, and aroma. In many fruits ripening occurs while the fruit is still attached to the parent plant, while in others such as the avocado, ripening takes place only following harvest. The complex physical and chemical changes of ripening have been studied extensively and techniques of handling and storage have evolved which can be satisfactorily applied to control the rate of ripening in the post-harvest period. While ripening normally occurs in fruit after growth ceases, it is a natural consequence of developmental changes during growth. This is evident from the fact that the time period from bloom to physiological maturity can be manipulated. A fruit is physiologically mature when the stage is set for ripening to ensue. The stage is set by the genetic makeup of the cultivar and the actors are the environmental conditions and chemical stimuli interacting during growth and development. Naturally occurring plant growth substances, their chemical analogs and antidotes, most certainly play a role in growth and development, and therefore must in some way influence the development of ripening capacity. However, the mechanism of their action has not been resolved, but this does not curtail speculation based on numerous observations which have been made. My purpose will be to briefly review the effects of certain plant growth substances on fruit ripening and suggest a possible role they may play in the process.

Open Access
Author:

Abstract

Widespread interest exists among horticulturists in the biosynthesis and mode of action of ethylene in relation to plant growth and development. The recent introduction of the ethylene-generating chemical, ethephon, has stimulated a tremendous amount of research broadly varying across many agricultural disciplines. Exogenous ethylene, supplementing that produced by the plant, has been found to exert diverse morphological and physiological effects, many of which may prove to be of horticultural importance. Depending upon the stage of plant development ethylene may; inhibit cell division and elongation, promote radial cell expansion and extend the growth period, promote flowering and modify sex expression, promote leaf and fruit abscission, and promote fruit ripening in addition to a myriad of other effects. Research at both the basic and applied level has contributed much to our current knowledge of ethylene's involvement in plant growth and development and has laid the ground work for future investigations.

Open Access

AVG, as ReTain™, an inhibitor of ethylene biosynthesis, was used alone or with a subsequent application of ethephon (Ethrel™), an ethylene-releasing chemical, to determine if red color development could be enhanced without over-ripening `Gala' and `Jonagold' apples. Treatments included: 1) AVG alone; 2) AVG followed by ethephon; 3) ethephon alone; and 4) control. Silwet L-77 surfactant was included in all treatments. Application of AVG delayed the onset of the ethylene climacteric and red color development of both cultivars. Application of AVG followed by ethephon similarly delayed the onset of the ethylene climacteric, but red color development at the commercial harvest date was only marginally reduced or not affected. The results were similar in both 1998 and 1999, although environmental stress during the growing seasons differed (1998—heat; 1999—moderate temperatures). The delay of fruit maturation and ripening observed at harvest following AVG +/- ethephon treatments improved storability of fruit in controlled atmosphere (CA) storage, as demonstrated by low internal ethylene levels after storage, and high retention of flesh firmness and shelf-life, while control fruit and those treated only with ethephon entered the ethylene climacteric during storage, and flesh firmness subsequently declined during shelf-life evaluation. Chemical name used: aminoethoxyvinylglycine (AVG).

Free access

AVG applied alone to `Gala' and `Jonagold' apples delayed maturity and the onset of the ethylene climacteric and delayed red color development. AVG followed by ethephon delayed maturity and the onset of the ethylene climacteric, but promoted red color development of both cultivars. Ethephon applied alone advanced maturity, ethylene production, ripening, and red color development compared to AVG alone. In other studies, the ripening-related effects of these treatments were reflected in the storability of fruit in CA storage. AVG - and AVG + ethephon-treated fruit were still at preclimacteric ethylene levels after 6 months in CA storage, with excellent retention of flesh firmness and shelf-life, while ethephon and control fruits had significantly higher ethylene levels and softened more during storage and shelf-life evaluation. Collectively, our results indicate that an ethephon application following AVG treatment may be useful to overcome the delay of red color development of apples treated with AVG only and that this can be achieved without overly stimulating fruit ripening. Thus, a once-over harvest of `Gala' and `Jonagold' apples may be achieved with a significant reduction in harvest costs. We attribute the promotion of red color development of apples receiving AVG treatment with a follow-up application of ethephon to the action of ethylene temporally-released from ethephon stimulating the development of the anthocyanin biosynthetic pathway, while AVG inhibits the development of the endogenous ethylene climacteric. Inhibiting endogenous ethylene production delays fruit from producing their own ethylene. We attribute maturation uniformity to the action of AVG allowing the less mature fruits to gain maturity while slowing maturity development of the more mature fruits. Improved storability of AVG + ethephon-treated fruit is attributed to the same ethylene-related phenomena.

Free access

Multiple harvests are often necessary to achieve maximum yield of well-colored high-quality apples. This is true for most cultivars, and particularly for `Gala'. Multiple harvests add significantly to the cost of producing apples. We tested our hypotheses that anthocyanin production of ReTain™-treated apples may be enhanced by ethephon without overly stimulating other ripening processes and ReTain™ may promote uniform maturation of apples within and between trees by delaying maturation and ripening processes. Experiments were conducted with `Gala', `Empire', and `Jonagold' apples at the MSU CHES in 1997 and 1998 employing the rootstock/training systems research plot. Treatments were 1) ReTain™ (50g/ac.) applied 3 to 4 weeks before harvest, 2) ReTain™ followed by ethephon (3/4 pt/ac.) applied 1 to 2 weeks before harvest, 3) ethephon, and 4) control (Silwet® L-77 surfactant only). ReTain™ applied alone delayed the onset of the ethylene climacteric and red color development of `Gala' apples. ReTain™ followed by ethephon delayed the onset of the ethylene climacteric and red color development at the commercial harvest date was not significantly affected. Similar results were obtained with the `Empire' and `Jonagold'. Results with ReTain™ and ReTain™ + ethephon in 1998 on `Gala', `Empire', and `Jonagold' apples were more profound than in 1997; we attribute this to less environmental stress on the trees, which were well-irrigated in 1998. The ripening-related effects of treatments were reflected in the storability of fruit 1997 in air and particularly during CA storage where the action of ethylene in ripening can be attenuated. ReTain™ - and ReTain™ + ethephon-treated fruit were still at preclimacteric ethylene levels after 6 months in CA with excellent retention of flesh firmness and shelf-life, while ethephon and control fruit had higher ethylene levels and softened more during storage and shelf-life evaluation.

Free access

We are investigating alternative strategies to control scald on apples. Ethanol vapors were applied to `Law Rome' and `Red Delicious' apples in the storage chambers by ventilating air through aqueous solutions of ethanol at different concentrations, and in modified atmosphere packages by adding various initial concentrations of ethanol vapor. Fruits in storage chambers treated with ethanol vapor at 1600 ppm for about 2 months showed no scald when stored for an additional period in air storage whereas the scald index in control was up to 2.33 (the highest is 3). The similar results in the modified atmosphere experiments confirmed that ethanol vapor could prevent apple scald. Ethanol vapor treatment was also correlated with a reduction of α-farnesene production by the fruits. α-farnesene is an isoprenoid metabolite in the pathway to carotenoid synthesis that has been implicated indirectly as a factor in scald development. Evidence for this based on diphenylamine (DPA) reducing the level of a conjugated terpene product of α-farnesene oxidation. Our results suggested that the control of scald by ethanol vapor treatment may be related to the reduction of α-farnesene production and its subsequent oxidation. Ethanol vapor treatment resulted in accumulation of ethanol in the fruits in direct proportion to the ethanol concentration administered and reduced the rate of ethylene production, and the internal ethanol levels dropped rapidly when fruits were returned to air without ethanol vapor.

Free access

In a 2-year study, induction of bitter pit-like symptoms (Mg2+ induced pits) on Northern Spy apples (Malus domestica borkh.) by infiltrating Mg2+ salt solutions into the fruits was positively correlated with bitter pit that developed during storage. Fruits at harvest were infiltrated with 0.1M MgCl2 in 0.3 M sorbitol with 0.1% Tween 20 and placed at 20°C for 10 days (d) after which the number of Mg2+ induced pits (MgIP) was determined on individual fruits. A parallel sample of fruits from each orchard was stored at 5°C in air (both years) and at 3°C in air or controlled atmosphere (CA) storage. The prediction was reliable for fruits harvested 20d and 10d before and at optimal maturity for long term storage. The endogenous (native) fruit Ca2+ concentration was inversely related to the number of pits induced by Mg2+ and to bitter pit development during storage. Pitting induced on the surface of fruits by Mg2+ treatment may thus be a reliable indicator of the potential of fruits to develop natural bitter pit.

Free access

Abstract

Investigations employing gases other than air, e.g. mixtures of O2, CO2, N2, C2H4, etc., in dynamic systems usually employ gas mixtures prepared in high pressure cylinders or by elaborate metering devices and mixing chambers using component gases from high pressure sources (1, 2, 3). Both systems require analysis of the resultant mixture to confirm that the composition is within the desired range. Physiological investigations often require thousands of liters of unique and portable gas mixtures. Commercially prepared mixtures in high pressure cylinders are expensive and metering systems are cumbersome. We have devised a simple method for rapidly preparing (ca. 10 min) dilute (μl/liter) gas mixtures in portable laboratory-owned cylinders at pressures of ca. 140 kg/cm2 (2000 psi). This method can also be used to prepare gas mixtures in percentage composition at lower pressures, ca. 70 kg/cm2 (1000 psi). This method uses a pressure differential between 2 cylinders of compressed gas to inject a known quantity of another gas from a connecting manifold into the lower pressure cylinder.

Open Access