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
The postharvest behavior of watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] fruit harvested at selected stages of development and stored in air or exposed to 50 μl ethylene/liter or 6500 μl propylene/liter was investigated. Characteristics measured included the effects of ethylene or propylene on ripening, respiration, ethylene production, and fruit firmness. Ethylene treatment induced a rapid deterioration of fruit at all maturation stages, as evidenced by the acute placental tissue softening and watersoaking. Melons of all maturation stages held in air showed little textural change throughout storage and produced only trace quantities of ethylene. Respiratory activity of fruit at each maturation stage was enhanced in the presence of ethylene or propylene and returned to normal rates upon removal of the gases. Ethylene production was not initiated by exposure of fruit to propylene, and was detected only in fruit exhibiting symptoms of decay. The results support the conclusion that watermelon fruit exhibit a nonclimacteric pattern of ripening.
Ripening of detached mature-green and black-ripe olives (Olea europaea L., cv. Conservolea) was studied during storage at 0, 5, 10, or 20 °C in air or air plus 100-200 μL·L-1 propylene. Green olive skin h° remained unchanged after 24 days at 0 or 5 °C in air or air + propylene, while olives partially lost their green color at 10 °C and developed purple color at 20 °C together with a substantial flesh softening. Propylene partially delayed flesh softening only at 10 °C. Respiration of green and black olives increased with storage temperature. Black olives had higher respiration rate than green olives. Propylene had no substantial effect on green or black olive respiration rate, except for an increase in respiration and ripening rates of green olives kept at 20 °C. Ethylene production rate of air- or air + propylene-treated green olives was almost undetectable. Black olives had higher ethylene production rate than green olives and this rate significantly increased with storage temperature. Addition of propylene had only minor effect on ethylene production of black olives. No climacteric respiratory rise or autocatalytic ethylene production was observed in green and black olives.
Abstract
The star apple is a nonclimacteric fruit and does not respond appreciably to treatment with ethylene, propylene, or ethephon. Its respiration rate at 20°C is 25 to 50 mg CO2 per kg-hr, and ethylene production ranges from 10 to 100 nl per kg-hr. Both respiration rate and ethylene production increased with the onset of fruit decay caused by species of Pestalotia and Diplodia.
Among the current methyl bromide alternatives under study, propylene oxide (Propozone) has shown potential to control soilborne diseases, nematodes, and weeds in polyethylene-mulched tomato. However, further research is needed to determine the appropriate application rates to control nutsedge in the crop. Also, the effect of this fumigant on tomato nutrient absorption has not been determined yet. Therefore, field trials were conducted for this purpose in Bradenton, Fla. Tested rates of Propozone were 0, 190, 380, 570, 760, and 950 L·ha–1 and were shank-applied in raised planting beds three weeks before `Florida 47' tomato transplanting. Examined data indicated that there was a rapid decrease in nutsedge density with 570 L·ha–1. For phosphorus (P) and potassium (K) foliar content, there was a linear increase of P concentrations as rate increase, whereas K content increased rapidly after 190 L·ha–1. The highest tomato yields were obtained with 760 and 950 L·ha–1 of Propozone.
Abstract
Ethylene and other olefinic compounds cause apples and other climacteric fruits to ripen. Propylene, which fruits do not produce, was employed to determine, 1) the stage of maturity apples must attain to autocatalytically produce ethylene, and 2) the effect of O2 tension on autocatalysis. ‘Red Delicious’ apples harvested at developmental stages representing 52, 58, 65, and 75% of maturity were gassed with propylene at concentrations of 0, 10, 50, 100, 500, and 1000 ppm for 1 week at 20°C. Propylene induced ethylene synthesis at all stages of maturity. Its ability to stimulate ethylene production, however, increased progressively with fruit maturation, although rate of production following treatment with 500 ppm propylene was constant. A shorter lag time to the onset of autocatalytic production was observed in more mature fruits which reflects a natural increase in sensitivity. Propylene administered at 6.5% O2 or less did not induce ethylene production, but an anaerobic atmosphere was necessary to completely inhibit ethylene synthesis in fruits once autocatalysis began.
Abstract
The respiratory rate, ethylene production and softening of untreated and treated (propylene or ethylene) avocado fruit (Persea americana Mill, cv Hass) were determined during growth and maturation using fruit harvested monthly from August to July. Untreated immature fruit harvested in August exhibited a climacteric, produced ethylene and softened after 18, 21 and 18.5 days, respectively. Treatment of these immature fruit for 1 to 3 days beginning 1 day after harvest stimulated respiration during the treatment, but the respiratory rate decreased to the level of the untreated fruit within 1 day after the treatment was terminated and they subsequently paralleled the response of the untreated fruit. Ethylene production was not induced by the treatment in immature fruit, but was in mature fruit. The climacteric peak rate and the peak rate of ethylene production increased as the fruit matured. The days to the climacteric peak and days to soften decreased as the season progressed. The ethylene or propylene treated fruit had a progressively shorter time to the climacteric and to softening as they matured compared to the untreated fruit.
Abstract
The relationship between the ripening behavior and C2H4 production of 4 slow-ripening nectarine [Prunus persica (L.) Batsch] genotypes was investigated. While there was no change in C2H4 production and little ripening in fruit kept for one month in air at 20°C, continuous exposure to 1300 μl·liter−1 propylene (C3H6) stimulated ripening and C2H4 production in these genotypes. The concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) in freshly harvested fruit was less than 0.05 nmol·g−1 and rose 6- to 8-times during the rise in C2H4 production. ACC levels remained low in preclimacteric fruit of all genotypes except P19-70, in which ACC concentration increased without an accompanying increase in C2H4 production. Wounding had little effect on C2H4 production by these 4 genotypes, but addition of one mm ACC stimulated C2H4 production by tissue plugs 35 to 70 fold. Delaying the harvest by up to 6 weeks had no effect on fruit weight or firmness, but flesh color and pH increased while titratable acidity and soluble solids content decreased; the onset of C2H4 production during storage at 20° was advanced, while the ability to convert ACC to C2H4 declined. In no case did C2H4 production rates by these fruit reach the levels of normal nectarine genotypes. We conclude that these slow-ripening genotypes lack the capacity to produce normal C2H4 levels for nectarines.
Ethylene production from florets of `Shogun' harvested broccoli (Brassica oleracea L.var. italica) held at 20C in darkness increased as the sepal tissues yellowed. The pattern of respiration rate and ethylene production from branchlets or entire heads was similar, although the magnitude of ethylene and carbon dioxide production appeared to be diluted by the other fleshy stem tissues. The reproductive structures, stamens and pistil, may have a role in determining the rate of sepal degreening, since removing them from florets reduced the yellowing rate. The pistil and stamens also had 7-fold higher levels of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity and more than double the ethylene production of other tissues within the floret. Stamen ACC oxidase activity was high on the first day after harvest, before yellowing became obvious. Changes in ACC oxidase activity of the pistil and stamens mirrored changes in ACC content in these tissues. The climacteric status of harvested broccoli was confirmed by exposure to 0.5% propylene. Propylene stimulated respiration and ethylene production and accelerated yellowing (measured as chlorophyll and hue-angle decline). Broccoli tissues did not respond to propylene immediately after harvest. In tissues aged in air before treatment, the time for response to propylene was shorter, a result suggesting a change in tissue sensitivity. Ethylene exposure induced a dose-dependent decline in hue angle, with 1 ppm ethylene giving the maximum response.
Abstract
‘Flamekist’ nectarine fruit [Prunus persica (L.) Batsch] picked during the slow-growth phase exhibited reduced C2H4 production in response to 1250 and 12,500 ppm C3H6 while fruit picked during the 2nd rapid-growth phase did not. Ethylene production by mature, preclimacteric nectarines during ripening in air at 20°C was stimulated by prior storage in air at 0° or exposure to 100 ppm C2H4 at 0° or 20°. Storage in air + C2H4 at 0° for longer than 4 days, however, nullified the stimulative effect. Subsequent peak-level C2H4 production was reduced by one-half compared to air-stored fruit. Concentration of 1-aminocyclopropane-1-carboxylic acid (ACC) increased along with C2H4 production rates during ripening. In mature fruit showing reduced C2H4 production, ACC accumulated above the expected level relative to control fruit. The data indicates that the inhibition of C2H4 production by C3H6 in developing nectarine fruit during the slow-growth phase is due to low availability of ACC, while in mature fruit the reduction in C2H4 production results from slowed conversion of ACC to C2H4.