Non-chilling Temperatures Research Articles

Effect of Temperature Conditioning on Chilling Injury of Cucumber Cotyledons

Endogenous abscisic acid levels and induced heat shock proteins were measured in tissue exposed for 6 hours to temperatures that reduced their subsequent chilling sensitivity. One-centimeter discs excised from fully expanded cotyledons of 11-day-old seedlings of cucumber (Cucumis sativus L., cv Poinsett 76) were exposed to 12.5 or 37 degrees C for 6 hours followed by 4 days at 2.5 or 12.5 degrees C. Ion leakage, a qualitative indicator of chilling injury, increased after 2 to 3 day exposure to 2.5 degrees C, but not to 12.5 degrees C, a nonchilling temperature. Exposure to 37 degrees C before chilling significantly reduced the rate of ion leakage by about 60% compared to tissue exposed to 12.5 degrees C before chilling, but slightly increased leakage compared to tissue exposed to 12.5 or 37 degrees C and held at the nonchilling temperature of 12.5 degrees C. There was no relationship between abscisic acid content following exposure to 12.5 or 37 degrees C and chilling tolerance. Five heat shock proteins, with apparent molecular mass of 25, 38, 50, 70, and 80 kilodaltons, were induced by exposure to 37 or 42 degrees C for 6 hours, and their appearance coincided with increased chilling resistance. Heat shock treatments reduced the synthesis of three proteins with apparent molecular mass of 14, 17, and 43 kilodaltons. Induction of heat shock proteins could be a possible cause of reduced chilling injury in tissue exposed to 37 or 42 degrees C.

Effects of Low Temperature on Ethylene Formation, Membrane Permeability and Fatty Acid Composition in Callus Derived from Apple(Malus pumila Mill. cv. Sensyu)Fruit.

The influence of low temperature on ethylene formation, membrane permeability, and free fatty acid composition were investigated in callus derived from 'Sensyu' apple (Malus pumila Mill.) fruits harvested at 71 days after full bloom (DAFB). 1-Aminocyclopropane-l-carboxylic acid (ACC) level, ethylene-forming enzyme (EFE) activity, and the rates of ethylene and carbon dioxide production in callus were stimulated by exposure to the low temperatures (-1°, 0°or 5°C). Electrolyte leakage and levels of free fatty acid in callus at chilling temperatures (-1°, 0°C) for 2 days were higher than those of callus stored at non-chilling temperatures (5°, 25°C). Thus, there seems to be a relationship between the increases in membrane permeability of callus chilled at 0°or -1°C and the release of fatty acids from intact membrane lipids.

Changes in lipids of tomato fruit stored at chilling and non-chilling temperatures

Mature green tomato fruits ( Lycopersicon esculentum) were stored at non-chilling or chilling temperature (15 or 2°, respectively) for 2, 4, 8 or 12 days after harvest. Fruit stored at 15° had progressed to the pink stage of ripening after 12 days, whereas fruit stored at 2° had not ripened significantly. On a fresh weight basis, the phospholipid content of tomato pericarp tissue changed very little during storage at either 15 or 2°. Free fatty acids increased three-fold in fruit held at 15° and 1.2-fold in fruit held at 2°. Total sterol content increased during storage at both 15 and 2°. The increase in free sterols was greater in chilled compared to unchilled fruit, whereas the reverse was true for steryl esters. Chilling had no efrect on the amounts of free and acylated steryl glycosides. The stigmasterol: sitosterol ratio in all steryl lipids increased dramatically with storage at 15°, but only slightly with storage at 2°.

Gene B Influences Susceptibility to Chilling Injury in Cucurbita pepo

The effects of gene B on susceptibility to chilling injury (CI) in two types of summer squash (Cucurbita pepo L.) were investigated. Two pairs of near-isogenic lines with (BB) and without (B+ B+) gene B were included in the study: `Caserta' (B+ B+) and `Precocious Caserta' (BB) of the vegetable marrow type, and `Benning's Green Tint' (B+ B+) and `Benning's Yellow Tint' (BB) of the scallop type. Respiration and ethylene evolution at nonchilling temperature were consistently higher in marrows than in scallops. Gene B had no influence on respiratory rates at nonchilling temperatures; however, the presence of gene B enhanced the chilling-induced stimulation of respiration in both marrows and scallops. Temporal differences in the patterns of chilling-induced stimulation of ethylene evolution indicated a greater sensitivity to chilling in marrows than in scallops and in both types in the presence of gene B. Electrolyte leakage was decreased by storage at chilling temperature in both marrow genotypes and was not influenced by storage temperature in B+ B+ scallops, but was increased by storage at chilling temperature in BB scallops. Therefore, electrolyte leakage was not a good CI index for these summer squash.

Physiological Changes in Yellow Summer Squash at Chilling and Nonchilling Temperatures

Abstract Summer squash (Cucurbita pepo L.) fruit were harvested 8 ± 1 day after anthesis and held at 2 or 15C. Samples were transferred from 2 to 15C after 3, 6, 9, or 12 days of storage. Respiration and ethylene production were measured 24 and 48 hr after fruit had been transferred to 15C. Electrolyte leakage from pericarp disks was determined 48 hr after transfer to 15C. Weight loss during storage was greater at 15 than at 2C; however, chilled fruit had a greater rate of weight loss after transfer to 15C than did nonchilled fruit. Surface pitting became obvious after 6 days at 2C and was progressively more severe with increased duration of chilling. Respiration rates of nonchilled fruit decreased with increased storage duration, whereas respiration rates of chilled fruit increased with increased storage duration. Ethylene production was <0.1 nl g-1hr-1 in nonchilled fruit. Ethylene production was enhanced in chilled fruit and increased with increased duration of chilling to a peak of 1.5 nl-g-1-hr-1 after 9 days at 2C, then decreased. Electrolyte leakage was not influenced by chilling.

Effect of low-oxygen storage on chilling injury and polyamines in Zucchini squash

Chilling injury of Zucchini squash ( Cucurbita pepo L., cultivar ‘Ambassador’) was reduced by a low-oxygen atmosphere. The extent of surface pitting after exposure to 2.5°C was less under 1% O 2 than when kept in air. The low-oxygen-stored squash also maintained higher levels of spermidine and spermine during storage at 2.5 or 12.5°C. Putrescine and spermidine in the skin tissue increased in response to exposure to chilling temperature. However, no significant increase of these polyamines was detected during storage at the nonchilling temperature.

Photoinhibition at Chilling Temperatures

Relative susceptibilities of chilled leaves to photoinhibition were determined for 15 species of crop annuals showing a wide range of chilling tolerance. Leaf tissue at 7°C was exposed to a moderate photon irradiance of 300 �mol m-2 s-1 and photoinhibition was measured by the decrease in chlorophyll fluorescence (Fv/Fm) measured at 77K. All chilling-resistant plants surveyed (barley, broad bean, oat, pea and wheat) were photoinhibited at chilling temperatures. The chilling-sensitive plants (bean, cucumber, lablab, maize, pearl millet, pigeon pea, sesame, sorghum and tomato) were more susceptible, the mean of values for susceptibility to photoinhibition being twice that of the chilling-resistant plants. Rice, however, showed a tolerance to photoinhibition at 7°C comparable to that of some of the chilling- resistant plants. Indica rices were more susceptible than japonica rices. Photoinhibition increased with decreasing temperature and with increasing photon irradiance in both the chilling-resistant and sensitive plants. In pea and cucumber, photoinhibition at 7°C was correlated linearly with the decrease in photosystem II activity assayed in chloroplast thylakoids isolated from similarly treated tissue. Relative tolerances of leaves of the same 15 species to chilling injury in the dark were also measured. No linear correlation was found between susceptibility of chilled leaves to photoinhibition and susceptibility to dark chilling injury. The pattern of differences between species for photoinhibition at 7°C was largely preserved when photoinhibitory treatments were given at a non-chilling temperature (21°C) by increasing the photon irradiance to 900 �mol m-2 s-1. We conclude that, while the chilling-sensitive plants were generally more susceptible than the chilling-resistant ones to photoinhibition at low temperatures, this arose from a greater sensitivity to the irradiance rather than from the chilling sensitivity. Photoinhibition associated with low temperatures was also demonstrated in the tropical fruit species, banana, pawpaw and Monstera. Low values of Fv/Fm recorded in leaves exposed to full sunlight during the winter month of July (range 0.39-0.56 compared with 0.70-0.79 in January) indicated that photoinhibition could adversely affect some tropical perennial fruit species cultivated in semitropical or warm temperate areas experiencing recurrent cool to cold winters.

Effect of temperature and light on ACC and MACC in chilled cucumber seedlings

The levels of the ethylene precursor, 1 -aminocyclopropane-1 -carboxylic acid (ACC) and its conjugate, 1 -(malonyl-amino)-cyclopropane-1 -carboxylic acid (MACC) in cucumber ( Cucumis sativus L.) seedlings at 20°C were higher after exposure to 5°C than after exposure to non-chilling temperatures. The chilled seedlings recovered from chilling-induced wilting after 24 h of warming at 20°C following 1 or 2 days of exposure to 5°C, whereas those exposed to 5°C for 3 days did not recover. Levels of ACC showed a corresponding increase and decrease as the seedlings were chilled and then recovered from the injury. However, MACC content remained elevated even after seedlings had recovered from chilling injury. The susceptibility of seedlings to chilling injury was affected not only by temperature, but also by light intensity. Seedlings exposed to chilling temperature at 5°C under higher photosynthetic photon flux density (PPFD) showed greater chilling injury than those exposed to the same temperature under lower PPFD. ACC and MACC levels, however, were comparable in different PPFD. These data suggested that the stimulation of ACC and MACC is a response to chilling stress, but their endogenous levels may not reflect the severity of chilling injury.

Electrolyte Leakage and Ethylene Production Induced by Chilling Injury of Papayas

Abstract Papayas (Carica papaya L.) were stored at 5° or 10°C for 1, 4, 7, 14, or 21 days. Chilling injury was detectable as visible skin discolorations after 4 days at 5°. Differences in electrolyte leakage and Hunter “L” values between fruit stored at 5° and 10° were not significant until after 7 days of storage. Fruit stored at 5° for more than 4 days also produced more ethylene upon transfer to warmer temperatures than did fruit stored at 10°. Differences in ethylene production between fruit stored under chilling temperatures, 5°, and nonchilling temperatures, 10°, increased with length of storage. Papayas chilled for 14 days at 5° retained a capacity to convert ACC to ethylene.

Responses of ‘Zucchini’ Squash to Storage in Low-O2 Atmospheres at Chilling and Nonchilling Temperatures

Abstract Zucchini squash (Cucurbita pepo L.) was stored 2 weeks at 2.5°, 5°, or 10°C and with 1%, 2%, 4%, 8%, or 21% O2 and then was aerated 2 days at 10°. Low O2 levels inhibited the rates of CO2 and ethylene production, particularly at 5° and 10°. Both rates increased during aeration, but much more in samples held previously at 2.5° or 5° than in those from 10°. About 75% and 55%, respectively, of the burst in CO2 production in samples from 2.5° and 5° was due to exposure to low temperature; the remainder was attributed to the effect of exposure to low O2 levels. For ethylene production, the corresponding values were about 95% and 70%. Zucchini squash stored at 5° for 2 weeks was virtually free of chilling injury (Cl), surface mold, decay, or off-flavors; almost all of the fruit still was rated good to excellent in appearance. About ¾ of the squash was still in this category after 2 additional days at 10°. At 5°, squash did not benefit from storage in low-O2 atmospheres. Storage at 2.5° induced severe Cl, which was ameliorated by holding the squash in 4%, 2%, or 1% O2 instead of in 21% or 8% O2. However, amelioration was no longer evident after 2 days of aeration at 10°. Defects not related to Cl—especially off-flavors—developed most noticeably in squash held at 10°; the benefit from low O2 levels was slight. Storing zucchini squash at 6° ± 2° likely would be optimal if it must be held longer than a few days.

Effects of Chilling on Respiration and Ethylene Production of ‘Hass’ Avocado Fruit at 20°C

Abstract The effects of chilling ‘Hass’ avocado fruit at 0° or 5°C on the respiratory rates, rates of ethylene production, ripening, and chilling injury symptoms at 20° were compared with the same responses of fruit exposed to a nonchilling temperature (10°) and fruit placed directly at 20°. Fruit held at 10° for 2 weeks were beginning the climacteric and ripened after about 4 days at 20°. Longer exposures at 10° resulted in ripe or overripe fruit. Fruit held for 2 weeks at 0° or 5° displayed normal climacteric patterns and ethylene production at 20°, and developed no significant chilling injury symptoms. Exposures of 4 and 6 weeks at 0° or 5° resulted in the development of chilling injury symptoms, abnormal ripening, atypical respiratory rate patterns, and reduced ethylene production rates which peaked after 2 days at 20° and showed a declining rate thereafter, with no increase in the rate of ethylene production associated with fruit softening.

Juice Characteristics and Internal Atmosphere of Waxed ‘Smooth Cayenne’ Pineapple Fruit1

Abstract Waxing fruit of fresh pineapple [Ananas comosus (L.) Merr.] with a polyethylene-paraffin mixture influenced a number of juice characteristics as well as internal fruit atmosphere composition. Juice pH declined less and total acidity increased less with increased storage at 8°C when fruit were waxed. Total soluble solids decreased from 16° to 15° Brix with 4 weeks storage at 8° with waxing having no effect. During the 3rd week at 8°, total ascorbic acid levels decreased from an initial value of 65 mg/liter juice to less than 5mg/liter in unwaxed fruit, and to 35 mg/liter in fruit waxed with 20% v/v wax-water. Increasing wax concentration increased the retention of juice ascorbic acid. Absorbance at 267 nm in unchilled fruit was related to shell color. Juice absorbance at 267 nm decreased with storage time, with a greater decline in more mature fruit, without effect from varying wax pH or percent polyethylene. The internal fruit gas atmosphere varied with coating concentration. Increasing the length of storage time to 4 weeks at 8° increased the size of respiration peak obtained when the fruit was removed to non-chilling temperatures (22°). Unwaxed fruit at 8° had less than 1% CO2 in the fruitlet locule, while waxed fruit contained 2 to 3% CO2. Upon transfer of fruit from 8° to 22°, internal CO2 increased to near 10% in unwaxed fruit and to 15 to 20% in waxed fruit.

MECHANISM OF HARDCORE FORMATION IN CHILL-INJURED SWEET POTATO (IPOMOEA BATATAS) ROOTS

Hardcore in sweet potatoes is caused by chilling followed by non-chilling temperatures and appears as hard tissue after cooking. Changes in pectic substances and the involvement of tissue softening by beta-elimination of pectic substances were studied in relation to hardcore development. Pectic substances from cell wall, middle lamella extracts of hardcore tissue resisted degradation by betaelimination. This resistance was associated with reduced esterification and increased levels of bound cations. The mechanism of hardcore formation appears to involve activation of demethoxylation during chilling and rapid demethoxylation of pectic substances when subsequently exposed to nonchilling temperature. Demethoxylated pectic substances and pectate salts may then restrict degradation by beta-elimination and concomitant softening during cooking.

Chilling-Induced Ethylene Production in Cucumbers (Cucumis sativus L.)

1-Aminocyclopropane-1-carboxylic acid (ACC) level, ACC synthase activity, and ethylene production in cucumbers (Cucumis sativus L.) remain low while the fruit are held at a temperature which causes chilling injury (2.5 degrees C) and increase rapidly only upon transfer to warmer temperatures. The increase in ACC synthase activity during the warming period is inhibited by cycloheximide but not cordycepin or alpha-amanitin. Our data indicate that the synthesis of ACC synthase, which results in increased ACC levels and accelerated ethylene production, occurs only upon warming, possibly from a message produced or unmasked during the chilling period. Ethylene production by chilled (2.5 degrees C) cucumbers increased very little upon transfer to 25 degrees C if the fruit were chilled for more than 4 days. The fruit held for 4 days or longer showed a large increase in ACC levels but little ethylene production even in the presence of exogenous ACC. This suggests that the system which converts ACC to ethylene is damaged by prolonged exposure to the chilling temperature. Cucumbers stored at a low but nonchilling temperature (13 degrees C) showed very little change in ACC level, ethylene production, or ACC synthase activity even after transfer to 25 degrees C.

Storage Behaviour of Ettinger, Fuerte and Hass Avocados Grown on Mexican Rootstock in Cyprus

SummaryThe storage behaviour of avocado cvs Ettinger, Fuerte and Hass was studied at 2.2°, 4.4°, 6.6° and 8.8°C for 0, 1, 2, 3, 4 and 5 weeks. Ettinger stored well for one week at 4.4°, 6.6° or 8.8°C, Fuerte for three weeks at 4.4°C and Hass for three weeks at 2.2° or 4.4°C. Chilling injury, internal darkening and the time required for ripening after removal to 20°C were the limiting factors determining the storage temperature and period for each cultivar. Chilling injury symptoms were visible during storage and not only after removal to 20°C. Internal darkening, observed at both chilling and non-chilling temperatures, increased with length of storage. Weight loss during storage or after removal did not cause any detrimental effect on quality. Ettinger was the most sensitive cultivar to chilling injury and Hass the least sensitive. The response to temperature of the three cultivars differed from that reported for same cultivars in other countries, depending on temperature and length of storage.

Effect of Chilling on Respiration and Volatiles of California Lemon Fruit

Abstract The respiration, ethylene production and ethylene, ethyl alcohol, and acetaldehyde content of the internal atmosphere of citrus fruit increased at 20°C following exposures to chilling temperatures (0° and 5°) compared with fruit placed directly at 20°C. The increases were greater the longer the exposure and greater following exposure to 0° than following exposure to 5°. Exposure to 12.8°, a nonchilling temperature, did not elicit a stimulation of these attributes when transferred to 20°. Ethylene, ethyl alcohol, and acetaldehyde in the internal atmosphere of fruit remained at the same levels during the chilling exposures. During storage at 12.8° the acetaldehyde content in the internal atmosphere increased, but the ethylene and ethyl alcohol content did not. The chilling injury sustained by citrus fruit during storage could be evaluated by transferring samples to 20° and determining the respiratory rate, ethylene production or the volatile content in the internal atmosphere 24 hours after transfer to 20°.

Respiration of Grapefruit and Orange Flavedo Tissue in Relation to Chilling and Non-chilling Temperatures and Respiratory Inhibitors1

Abstract One theory on the mechanism of chilling injury of tropical and subtropical fruits is that aerobic respiration is impaired at chilling temperatures and injury occurs from consequent accumulation of fermentation products. Therefore, O2 uptake and CO2 evolution by the flavedo (colored portion of peel) of chill-sensitive grapefruit (Citrus paradisi Macf.) and chill-resistant orange (Citrus sinensis (L.) Osbeck) tissue were measured by a manometric Warburg technique over a range of chilling and non-chilling temperatures to see if there were differences in respiratory activities of the 2 tissues. A break in the Arrhenius plot of CO2 evolution and O2 uptake by grapefruit tissues occurred at 12°C but no break was apparent in similar plots for orange tissue. Respiratory quotients for both orange and grapefruit were lower at chilling than non-chilling temperatures. When O2 uptake was determined in the presence of maximal inhibitory levels of cyanide and salicylhydroxamic acid, a large residual O2 uptake remained. At chilling temperatures, in the absence of cyanide, salicylhydroxamic acid reduced O2 uptake by grapefruit flavedo tissue by 30% but had no effect on O2 uptake by orange flavedo tissue in the absence of cyanide. The results indicate that extra-mitochondrial oxidases may have a role in chilling injury of grapefruit flavedo.

ROLE OF PECTINESTERASE AND POLYGALACTURONASE IN THE FORMATION OF WOOLLINESS IN PEACHES

ABSTRACTChilling injury symptoms do not appear in nonripe peaches (Prunus persica L.) while stored at low temperatures, but a dry‐mealy texture (woolliness) appears in chill‐injured fruits after ripening. Reduced pectinesterase and polygalacturonase activities were associated with reduced juiciness, reduced levels of water soluble pectins, poor texture and enhanced levels of insoluble pectins in peaches which were ripened after storage at 1°C for more than 3 wk. Pectinesterase and polygalacturonase activities and levels of pectic substances were unaltered in nonripened fruits held at 1°C. Fruits transferred to 20°C for 24 or 48 hr after 1 and 3 or 2 and 4 wk of storage at 1°C did not exhibit woolliness after 5.5 wk of storage. Warming for 12 hr was inadequate to prevent the development of woolliness. The effect of intermittent warming on providing a desirable texture in subsequently ripened fruits was related to enhanced pectinesterase and polygalacturonase activities. Low temperatures appeared to induce this physiological disorder by reducing the capacity to provide adequate levels of pectin‐esterase and polygalacturonase during subsequent ripening at nonchilling temperatures. Intermittent warming appeared to prevent injury by protecting the capacity to produce adequate levels of pectolytic enzymes during ripening.

Hardcore in Sweet Potato Roots as Influenced by Cultivar, Curing, and Ethylene1

Abstract Hardcore in sweet potato roots (Ipomoea batatas (L.) Lam) is induced by chilling and subsequent exposure to nonchilling temperatures prior to cooking. The defect is detected only after cooking and could adversely affect consumer acceptance and utilization. Of seven cultivars tested, ‘Red Jewel’ and ‘Jewel’ were the least susceptible to hardcore, while ‘Georgia Jet’ and ‘Jasper’ were the most susceptible. Cured roots were more susceptible than those freshly harvested in all cultivars except ‘Centennial’. Exposure to ethylene during the post-chilling induction period did not reduce the incidence of hardcore but significantly reduced its severity.

Induction of Textural Changes in Sweet Potato Roots by Chilling1

Abstract Hardcore was apparent in cooked sweet potatoes (Ipomoea batatas Lam.) which had been chilled and transferred to nonchilling temperatures prior to cooking. The severity increased with duration of chilling at 2°C. Hardcore was not observed in roots boiled immediately after chilling, although these roots were firmer than those not chilled. Enhanced levels of pectic substances, soluble in sodium hexametaphosphate, were associated with hardcore tissue, while starch, protopectin, and hemicellulose were related to enhanced firmness of continuously chilled roots. No differences in pectinmethylesterase activity were observed between storage treatments. Reduced levels of alpha amylase activity in continuously chilled roots probably accounted for the enhanced levels of starch after the roots were processed. From data on U.V. absorption, phenolic levels, and electrolyte leakage, we believe that hardcore develops when phenolics or related substances, and possibly cations, bind with cell wall materials.