Abstract
Preharvest treatment with 400 ppm aminoethoxyvinylglycine (AVG) delayed the ripening of ‘Bartlett’ pears kept at 20°C. The effect was not uniform, with the delay in ripening ranging from a few to 112 days. Prolonged storage at 20° was accompanied by a relatively steady, low level of respiration, gradual degreening, and partial suppression of the eventual climacteric. The combined effect of AVG treatment and prolonged ‘nonripening’ storage at 20° led to a marked attentuation of the production of 4 readily measurable volatiles including methyl-, ethyl-, and hexylacetate as identified by cochromatography and combined gas chromatography–mass spectrometry. Surprisingly, prolonged storage resulted in a much increased production of 2 other volatile fractions when AVG inhibition was reversed by C2H4 treatment. The emanation of all measured volatiles was closely coincident with the climacteric peak. These observations confirm prior reports of disuniform effects of preharvest AVG treatment and reveal that metabolic transitions during prolonged, nonripening storage may have adverse effects on fruit quality.
Abstract
Ethylene dibromide (EDB) fumigation of fruit of tomato (Lycopersicon esculentum Mill.) reduced red color development in the outer pericarp, although the inner tissues remained unaffected at EDB doses as high as 35 g/m3. Carotene accumulation was enhanced by EDB at 4 g/m3, but at higher doses the carotene content of the tomato pericarp was reduced. Skin puncture force was reduced in green fruit fumigated at 4 g/m3, but not in breaker or pink fruit; higher skin puncture forces were recorded at higher doses for the three fruit maturities tested, EDB stimulated the respiration of preclimacteric fruit, but fruit fumigated just prior to the climacteric showed a normal respiration peak, although a 4 g/m3 treatment resulted in partial climacteric respiratory rise.
Abstract
The respiratory rate, ethylene production and ripening of mature ‘Hass’ avocado fruits (Persea americana Mill.) were determined at 20° to 40°C. Typical climacteric patterns occurred at 20°, 25°, 30° and 35° with the climacteric maximum increasing with temperature, but only a decreasing respiratory rate with time was observed at 40°. Maximum ethylene production decreased as the temperature increased, with a significant decrease between 25° and 30°, only trace amounts were produced at 35° and essentially no ethylene production was detected at 40°. The ripened fruit quality was excellent at 20°, 25° and 30°, fair at 35° and abnormal and unacceptable at 40°. Fruit held at 40° for up to 2 days resumed ripening when transferred to 20°. The exposure to exogenous ethylene or propylene hastened the ripening response up to 35°, however at 40° the respiratory rate was increased, but ethylene production and normal ripening did not occur.
Abstract
Amylase activity in detached avocado fruit (Persea americana Mill. cv. Fuerte) was directly correlated with ripening processes such as the climacteric rise in respiration, ethylene evolution, and softening. The term amylase designates the total amylolytic activity of avocado fruit but its exact nature was not studied. Amylase activity was higher in young than in mature fruits. After harvest, amylase activity started to rise with the onset of the respiratory climacteric. Parallel to the increase in amylase, a decrease in the starch content of the fruit pulp was observed. The disappearance of starch during softening was also demonstrated by electron microscopy. The possible role of starch as substrate and that of amylolytic activity as energy supplier, for metabolic processes in the fruit, is discussed.
The opening and senescence of gladiolus (Gladiolus sp.) florets was accompanied by climacteric or nonclimacteric patterns of respiration and ethylene production, depending on variety, and whether data were expressed on a fresh-weight or floret basis. A climacteric pattern of ethylene production by the youngest buds on the spike (which never opened) was stimulated by cool storage, and was not affected by holding the spikes in a preservative solution containing sucrose. Ethylene treatment had no effect on senescence of the florets of any of the cultivars tested. Pulse treatment of the spikes with silver thiosulfate (STS) improved floret opening but not the life of individual florets. Sucrose and STS had similar but not synergistic effects on floret opening, suggesting that STS improves flower opening in gladiolus by overcoming the effects of carbohydrate depletion.
Abstract
Gamma irradiation up to 100 Kilorad (Krad) caused no immediate visual damage to fruits of avocado (Persea americana Mill.). Twenty Krad or more stimulated a climacteric-like rise in respiratory rate. Rates of ethylene (C2H4) production were related directly to dose up to 40 Krad. Ten and 40 Krad delayed the climacteric peak for 3 days. Softening was delayed by 10 Krad and hastened by 40 and 100 Krad. At 100 Krad, ripening was lacking and the fruit severely injured. No benefit remained from any dose after 3 weeks of storage. Storage reduced the time required for ripening by 2 days, and enhanced the development of injury symptoms and pigment degradation.
Banana [Musa sp.9AAA group0, Cavendish] fruit are climacteric in nature, undergoing a rapid rise in ethylene production and respiration. Ethylene production can peak within 8 h of a detectable rise in production and respiration peaks within 24 h. These rapid changes permit precise timing for events related to or dependent on ethylene presence. Using rapid analytical methodology, we investigated the dynamic changes in volatile biosynthesis and its relation to other ripening parameters. Ungassed, mature-green banana fruit were placed individually at 23°C in flow through glass chambers. Ethylene production, respiration, chlorophyll fluorescence, skin color (hue angle) and volatile production were monitored. The climacteric rise and subsequent fall in ethylene production was found to be complete within 20 h. The respiratory rise peaked 20 h after the initial rise in ethylene production. The onset of the decline in chlorophyll fluorescence, skin color (hue angle) were coincident with the rise of ethylene and respiration, which indicated that the chlorophyll fluorescence may be used to monitor the banana fruit ripening. Volatile production was found to begin ≈60 h after the onset of the ethylene climacteric, peaking 3 to 4 days later. The ester precursors butyric acid and 3-methylbutanol were used in feeding experiments at different developmental stages for pulp and peel. Full ester-forming capacity was found to exist well before the onset of volatile biosynthesis. There were also different biosynthetic capacities for pulp and peel. Low aroma production in pre-climacteric fruit is apparently limited by the supply of precursors, which may be derived from the ethylene-induced enhancement of fruit respiratory metabolism.
We have studied the effects of MCP and low O2, applied singly and in combination, on apple fruit ripening at 1, 7, and 18 °C. The single application of 2 ppm MCP is more effective in delaying the onset of the C2H4 climacteric than is 1% O2. However, the combined application has a much larger effect than the single applications of either MCP or 1% O2. For instance, at 7 °C, the onset of the C2H4 climacteric occurs at 15, 50, and 90–95 days for the controls, 1% O2 and 2 ppm MCP, respectively, whereas the combined application of 2 ppm MCP and 1% O2 suppressed the initiation of the C2H4 climacteric for 200 days, the duration of the experiment. The retardation of the climacteric onset by the treatments is associated with the suppression of ACC-synthase (ACS1) and the putative receptor ERS1. The accumulation of their transcripts is critically dependent on the rate of C2H4 evolution. As expected, the combined application of MCP and 1% O2 completely suppressed the expression of both genes. Yet when the fruits were transferred to 18 °C in air, they ripened normally. A similar pattern of inhibition in response to the above treatments was also observed with a C2H4-dependent MAPK. The expression of ETR1, ETR2 and ACC-oxidase was not affected by the treatments. The nature of this strong effect of the combined application of MCP and low O2 is not clear. It should be pointed out that MCP does not inhibit the induction of hypoxic proteins such as ADH.
Abstract
Treatment of ‘d'Anjou’ pears (Pyrus communis L.) with high CO2 atmosphere for a short period immediately following harvest prolonged storage life, retarded ethylene production, delayed the climacteric rise in respiration, reduced loss of malic acid, suppressed increase in protein N, retained firmness, quality and the capacity to ripen after long storage. Treatment with 12% CO2 for 2 or 4 weeks provided the best results without injury.
Abstract
Pimiento peppers from all ethephon treatments had a faster rate and a higher percentage of coloring than peppers receiving the ethylene treatment or the control. The completely green peppers, however, did not color to an acceptable commercial grade within 96 hr.
Ethephon induced a climacteric in the respiration of the treated detached peppers that was not present in the control fruits, indicating that metabolism was affected as the coloring rate was increased.