Search Results
Abstract
Extraction and assay of sorbitol dehydrogenase (SDH) throughout fruit maturation of 3 apple (Malus domestica Borkh.) cultivars, watercore-resistant ‘Golden Delicious,’ occasionally susceptible ‘McIntosh’, and normally susceptible ‘Starkrimson,’ showed no relationship between susceptibility to watercore and extractable enzyme activity. There was, however, a relationship between increased SDH activity and onset of the climacteric as measured by ethylene and CO2 evolution, suggesting that SDH, like certain other enzymes, increases during maturation.
Abstract
Gas chromatography and bioassays were used to identify ethylene (C2H4) in fruit emanations of mammee apple (Mammea americana L.). C2H4 production probably triggered the respiratory rise in preclimacteric fruit and its relationship to respiration was typical of that for a climacteric fruit. C2H4 production was however, independent of respiration in immature and postclimacteric fruits. C2H4 production increased to a peak and then declined with deterioration of fruit in spite of nearly constant rates of respiration in immature fruit and declining rates in postclimacteric fruit. Peak production of C2H4, 408 μl per kg per hr, from preclimacteric fruit is probably the highest reported among fruits.
Abstract
Chilling sensitivity of ‘Fuerte’ and ‘Hass’ avocados (Persea americana Mill.) is a function of the stage of the climacteric. The least sensitive stage is postclimacteric where fruit can be kept at 2°C for 6 to 7 weeks. ‘Hass’ avocados on the climacteric rise and at the climacteric peak were most sensitive to chilling and showed injury after 19 days of treatment at 2°. Postclimacteric fruit could be transferred to 2° at 36 to 48 hours after the climacteric peak. The time preclimacteric fruit could be held at 2° varied during the picking season but could be as long as 30 days.
Autocatalytic C2H4 biosynthesis in preclimacteric apple fruit (Malus domestica Borkh. `Golden Delicious') was prevented by storage in atmospheres of 20% CO2-enriched air (17% O2 + 63% N2) or 0.25% O2 (balance N2). In preclimacteric fruit, both treatments inhibited C2H2 biosynthesis by suppressing expression of ACC synthase (ACC-S) at the mRNA level. ACC oxidase (ACC-O) mRNA abundance and in vitro enzyme activity also were impaired by these treatments. However, the conversion of ACC to C2H4 never became the rate limiting step in C2H4 biosynthesis. C2H4 biosynthesis also was effectively inhibited in climacteric apple fruit kept in air + 20% CO2 or 0.25% O2. Climacteric apples also exhibited suppressed expression of ACC-S at the mRNA level, while ACC-O transcript abundance, enzyme activity, and protein abundance were reduced only slightly. ACC-S is the key regulatory enzyme of C2H4 biosynthesis and is the major site at which elevated CO2 and reduced O2 atmospheres inhibit C2H4 biosynthesis, irrespective of fruit physiological maturity. Chemical names used: 1-aminocyclopropane-1-carboxcylic acid (ACC).
Abstract
The parameters for optimum maturity of fruit of ‘Pairi’ variety mango, harvested near Mysore from 1964 to 1969, have been found to be 260 ± 20 g in weight, olive green surface color, and outgrown shoulders. In addition, pH and color of the pulp in terms of chromaticity coordinate x were useful indices. Other parameters were not consistent.
Respiration climacteric maximum was delayed in immature fruits and advanced in over-mature fruits. Fruits of optimal maturity recorded the climacteric maximum on the 9th day ± 1 at ambient storage of 26 ± 2°C and 45–65% RH. Sugar accumulation was maximum at about the time of the climacteric peak in respiration and sucrose was predominant. The chemical composition of the fruit was more or less similar over several seasons and harvests.
Fluorescent products (lipofuscin-like compounds) of lipid peroxidation, which accumulate with age, were extracted from `Fuerte' avocado (Persea americana Mill.) peels during ripening. Fractionation and analysis of these fluorescent compounds (FCs) was carried out by an improved method, based on separation of FCs from-chlorophyll by Sep-Pak silica cartridges. A sharp rise in FCs content was found 2 days after harvest in avocado fruits stored at 22C, and ethylene enhanced this rise 3-fold on the 4th day. The accumulation of FCs preceded by at leasts days the onset of climacteric ethylene and respiration and by 2 days the decrease in fruit firmness. Moreover, a 6-foId increase in the FCs concentration occurred during 1 to 2 weeks of storage at SC, but the avocado fruits did not show any other detectable signs of ripening. These results suggest that lipid peroxidation may be regarded as one of the earliest detectable processes occurring during fruit ripening. Thus, an increase of FCs in peel may be employed as a horticultural characteristic for estimating initiation of ripening in avocado fruit.
A strong association is implicit between mitochondrial function and the energy demands of cells responding to stress. Yet, the dynamics of this organelle-cellular dependency have been difficult to resolve. This study examines a new diagnostic parameter namely, mitochondrial maintenance and self-restoration as exhibited by the course of respiratory functions (states 3 and 4 respiratory rates, respiratory control) of mitochoudria extracted during and after exposure of intact `Hass' avocado (Persea americana) fruit to different stress atmospheres: anoxia (100% N2) or high (25% and 75%) CO2 for varying durations. Comparisons are made with direct exposure of the mitochondria themselves to similar atmospheres. In general, exposure of the fruit to CO2 rich atmospheres enhanced the capacity of their mitochondria to restore energy-linked functions whereas anoxia caused irreparable damage. The physiological (climacteric) state of the fruit also affected the stress capacity of the mitochondria contained therein, anaerobiosis being more harmful to mitochondria in riper fruit. In contrast to their effects in vivo, in vitro anoxia appeared to sustain mitochondrial energy-linked functions, whereas high CO2 was clearly harmful. These and other observations are discussed in the context of mitochondrial self-restoration or homeostasis and its relevance to postharvest stress-atmosphere storage for purposes such as pathogen suppression or insect control.
Abstract
‘McIntosh’ and ‘Cortland’ fruits were harvested at 3—4 day intervals and ‘Delicious’ and ‘Golden Delicious’ fruits were harvested at 5 day intervals in several seasons. The respiration rate was measured 24 hr after each harvest in order to locate the position of the fruit on the respiratory climacteric curve. The optimum harvest dates for each variety were determined by evaluations of the quality and condition of the fruit after removal from storage. Optimum harvest dates were not found to be associated with any definite position on the climacteric curve.
Abstract
‘Humble’ blackberry (Rubus arvenis Bailey) extractable ethylene content reached more than 7.0 mg/liter shortly after full bloom and dropped to well under 1.0 mg/liter for the remainder of fruit development. The low ethylene levels during the latter stages of fruit development suggests that blackberries are nonclimacteric. ‘Tifblue’ rabbiteye blueberry (Vaccinium ashei Reade) extractable ethylene was more than 5.0 mg/liter approximately 2 weeks after bloom, declined to near 1.0 mg/liter during green fruit development and peaked at 3.7 mg/liter in reddish-green (ripening) berries. The increased level of ethylene in ripening fruits suggests that rabbiteye blueberries are climacteric.
Abstract
Mature green bell pepper fruit (Capsicum annuum L. cv. Yolo Wonder) exhibited a non-climacteric pattern of ethylene and carbon dioxide production during normal ripening and red color development at 24°C. Exposing detached mature green fruit to 500 ppm propylene in air for 48 hours, did not induce an increase in ethylene or carbon dioxide production. Wounding excised plugs of ovary wall tissue caused an increase in carbon dioxide production within one day, and an increase in ethylene production by the second day.