Non-chilling Temperatures Research Articles

Catalase enzyme activity is related to tolerance of mandarin fruits to chilling

The effect of a postharvest hot-water dip treatment (HWT) at 53°C for 3 min and a 3-day heat-conditioning treatment at 37°C with air (HAT) at 90–95% RH on chilling tolerance and catalase (CAT) activity was compared in ‘Fortune’ mandarins. The HWT treatment increased CAT activity in the fruit, but after they were removed from high temperature to cold storage a rapid decline in CAT activity was associated with increased chilling injury. Greater chilling tolerance and CAT activity was induced when fruits were conditioned for 3 days at 37°C and 90–95% RH. The CAT activity in fruits exposed to HAT was higher than in the dipped and the non-heated fruits over the storage period at 2°C. An inhibitor of CAT activity, 3-amino-1,2,4-triazole (AT), caused peel damage in HAT ‘Fortune’ mandarins and in the chilling-tolerant ‘Clementine’ and ‘Clemenules’ cultivars stored at 2°C but not at 12°C (non-chilling temperature). CAT activity was reduced about two to three times by AT upon cold storage in the cultivars studied. Little difference was found in the activity of ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD) between AT-treated and non-treated fruits. The data indicate that CAT may be a major antioxidant enzyme involved in the defence mechanism of mandarin fruits against chilling stress. Our results also suggest that the different effectiveness of the heat-conditioning treatments in increasing chilling tolerance of ‘Fortune’ mandarins may be related to induction of CAT activity during heating and on its persistence during cold storage.

Accumulation of PAL transcript and PAL activity as affected by heat-conditioning and low-temperature storage and its relation to chilling sensitivity in mandarin fruits.

The effects of different periods of heating at 37 degrees C on phenylalanine ammonia-lyase (PAL) and how this relates to chilling tolerance was investigated in fruits of the chilling-sensitive Fortune mandarin. All effective heat-conditioning treatments caused an early and transient increase in PAL mRNA and PAL activity. Conditioning fruits at 37 degrees C for 1 or 2 days prevented the manifestation of chilling symptoms but not the accumulation of PAL mRNA and PAL activity observed in untreated fruits. In fruits conditioned for 3 days, cold-induced damage and PAL activity were also suppressed but not the accumulation of PAL transcript upon subsequent storage at 2 degrees C. Storage of 3-day-heated fruits at a nonchilling temperature (12 degrees C) induced an early and transient increase in both PAL mRNA and PAL activity. High levels of PAL transcript and PAL activity were detected in freshly harvested fruits of a chilling-resistant mandarin (Hernandina) that decreased upon cold storage at 2 degrees C in heat-treated and nontreated fruits. These results indicate that sensitivity of mandarins to chilling correlates with low constitutive levels of PAL mRNA and PAL activity and with the inducibility of both upon exposure to low temperatures.

Involvement of phenylalanine ammonia-lyase in the response of Fortune mandarin fruits to cold temperature

L-phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) is generally recognised as a marker of environmental stress in different plant tissues. To investigate the involvement of PAL in the response of citrus fruits to cold temperature, changes in the abundance of PAL mRNA and PAL activity were examined in flavedo tissue of the chilling-sensitive Fortune cultivar (Citrus elementina Hort. ex Tanaka × Citrus reticulata, Blanco). A cDNA library was constructed from flavedo tissue of chilling-stressed fruits and screened with a 660 bp PAL probe, obtained by polymerase chain reaction using oligonucleotides derived from conserved sequence regions. Two fulllength cDNA clones (FPAL1 and FPAL2) were isolated, and the deduced amino acid sequences showed a 75-85% similarity with PAL genes from other plant species. A comparative analysis of the changes in PAL activity and PAL mRNA levels was conducted in fruits stored at chilling (2°C) and non-chilling (12°C) temperatures. Northern blot analyses, using both FPAL1 and FPAL2 cDNAs as probes, recognised a single mRNA that accumulated in fruits exposed to 2°C prior to the appearance of physical chilling symptoms and the accompanying increase in PAL activity. Once symptoms were obvious, accumulation of PAL transcript and PAL activity were restricted to the tissue in and around the necrotic regions. However, exposure to a low non-chilling temperature produced an early, moderate and transient increase in PAL mRNA levels and PAL activity that declined after 1 day. This transient induction of both PAL gene expression and activity could be part of a rapid adaptive response of the tissue to low temperatures. Interestingly, a rapid and sustained accumulation of PAL transcript occurred in the leaves and roots of citrus plants exposed to a low temperature in the absence of any detectable chilling-induced damage.

Ripening Affects High-Temperature-Induced Polyamines and Their Changes during Cold Storage of Hybrid Fortune Mandarins

Polyamine levels were measured in the flavedo of three ripening stages of Fortune mandarins exposed to high-temperature conditioning before storage at a chilling (2 °C) and a nonchilling temperature (12 °C). Increasing periods of conditioning at 37 °C delayed the development of chilling injury (CI) and produced an increase in the content of the polyamines in the following proportion: spermine > spermidine > putrescine. Storage at 2 °C of conditioned fruits reduced the polyamine titer to levels similar to those of nonconditioned fruits. Changes in polyamines during storage of conditioned and nonconditioned fruits were dependent on the ripening stage of the fruit. In general, the levels of polyamines in nonconditioned fruits stored at 2 and 12 °C were similar. No change in spermine was induced in the most mature fruits at 2 °C or in response to high-temperature conditioning despite conditioning-reduced CI. With this exception, the data indicate that conditioning fruits at 37 °C elevated the content of poly...

Ethylene Production by `d' Anjou' Pears during Storage at Chilling and Nonchilling Temperature

To determine the ability of `d' Anjou' pear fruit to produce climacteric ethylene postharvest, fruit were harvested at a mature green stage, chilled at -1 °C for various times, then transferred to 20 °C to ripen. In addition, fruit were first held at 20 °C for various times, then at –1 °C for various durations, followed by transfer to 20 °C for 11 days. As storage time at –1 °C increased from 0 to 70 days, the time required to induce climacteric ethylene when transferred to 20 °C progressively decreased from 90 to 0 days. The total storage time (sum of d at chilling and nonchilling temperature) needed to induce climacteric ethylene remained nearly constant (70 to 90 days). However, this was not the case with fruit held initially at 20 °C, then transferred to –1 °C. The total storage time needed before the pears produced climacteric ethylene ranged from 70 to 110 days and increased with time of storage at 20 °C. These fruit required more time at –1 °C than those first stored at –1 °C. The chilling requirement mechanism of `d' Anjou' pears remains intact even during storage at nonchilling temperature and diminishes with senescence.

Fourier transform infrared spectra of zucchini squash stored at chilling or non-chilling temperatures

Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that might be suitable. Fourier transform infrared spectroscopy (FTIR) was used to investigate spectral changes in the epidermis of zucchini squash resulting from low temperature storage-chilling (5°C) or non-chilling (15°C). Increased levels of fluid (water) were found in the tissue after 2 days of 5°C storage. This increase was reversed to harvest levels when chilled squash were warmed to room temperature for 1 day. After 3 days at 5°C and 1 day at room temperature, a further increase in fluid levels was found in the epidermis. Squash chilled for 3 days were apparently beyond recovery as indicated by spectral changes, although visual symptoms of chilling injury were not apparent until another 3 days of exposure to 5°C. Spectra of epidermis tissues from squash stored at 15°C indicated a pattern of increased non-reversible fluid accumulation when storage was prolonged. These results suggest that FTIR spectroscopy may be a rapid way to detect changes in chilled tissues before the eventual appearance of visible symptoms.

Heat treatment to decrease chilling injury in tomato fruit. Effects on lipids, pericarp lesions and fungal growth

Tomato fruits are sensitive to low temperature and develop chilling injury, while at nonchilling temperatures they ripen rapidly. Previously, a hot‐air treatment was found to reduce the sensitivity of the fruit to low temperatures. In the present study hot air was compared to hot water and their effects on reducing chilling injury and fungal decay were investigated. Tomatoes (Lycopersicon esculentum cv. Daniella) at the breaker stage were subjected to hot air, 48 h at 38°C, or various hot water dips, 30 min at 40°C or 2 min at 46, 48 or 50°C, before holding at 2°C. The unheated tomatoes developed chilling injury and fungal infections at 2°C, but not at 12°C. All the heat treatments reduced chilling injury and decay in tomatoes held for 3 weeks at 2°C. The outer pericarp tissue of heated tomatoes had higher phospholipid and lower sterol contents than unheated tomatoes. Heated tomatoes also had less saturated fatty acids than unheated tomatoes held at 2°C, but not at 12°C. Scanning electron micrograph observations showed that all the fruits had microcracks in their surface, but the unheated chilled tomatoes had also fungal growth in the cracks, while those of the heated tomato fruit did not. In the areas of chilling injury collapsed cells were present under the peel and could also support pathogen development. It is suggested that the heat treatment institutes a response to high temperature stress in the fruit tissue that leads to strengthened membranes. This prevents the loss of function and cell collapse which was found in the chilling‐injured areas of affected fruit.

Qualities of Hot Water- and Calcium-treated Tomatoes after Storage

Mature green tomatoes (cv. Vibelco) were immersed in water at 42°C for 90 min or in water (42°C for 90 min) containing 2% calcium chloride prior to storage at 2 and 15°C for 2, 4, and 6 weeks. Control fruits were immersed in 20°C water for 90 min. All fruits were subject to poststorage ripening at 20°C for 6 days. Weight loss, chlorophyll and lycopene content, pH, TSS, TA, firmness, and electrolyte leakage were determined after storage or 6 days after storage. Control fruits showed lower weight loss, less lycopene content, pH, TSS, firmer but more chlorophyll content, pitting, decay, TA, and electrolyte leakage than treated fruits. Compared to hot water-treated fruits, lower pitting, decay, less chlorophyll content, and electrolyte leakage while more lycopene content, TA, and firmness were detected in combine hot water- and calcium-treated fruits. Extended storage time resulted in higher pitting and decay. Fruits stored at chilling temperature (2°C) showed higher chilling susceptibility to pitting and decay than those were stored at nonchilling temperature (15°C).

Effect of Reduced Temperatures on Melon Transplant Subsequent Growth and Survival

Delays in transplanting vegetable seedlings are often a problem due to cold, wet spring weather. This results in the production of overgrown transplants, which are more difficult to transplant and often do not survive. The objective of this study was to find a non-chilling temperature at which to short-term-treat transplants in order to slow down vegetative growth. `Superstar' muskmelon and `Royal Jubilee' watermelon seedlings were greenhouse-grown at 20°C during Mar. 1996. Fifty-cell trays of transplants were grown to the first true leaf stage and then held in a dark cooler at 7.5 or 12.5°C for 4 to 8 days. Control plants were kept in the greenhouse. Transplants were repotted into larger pots after the treatment. Preliminary experiments revealed that 8 days of 7.5°C was too severe of a temperature for watermelon and cantaloupe transplants. Six days of 7.5°C was effective in significantly reducing stem and leaf area growth without seedling death for both types of melons. Shorter durations at 7.5°C or the same duration at 12.5°C was less effective in retarding stem elongation. Surface area of the transplant leaves, after the reduced temperature treatment and subsequent growth, was much more sensitive to a drop in temperature and the length of temperature treatment. In 1997, these treatments will be repeated in the greenhouse and also in the field.

Differential propylene induced ethylene production in ‘Anjou’ pears during storage at chilling and non-chilling temperatures

Summary‘Anjou’ pears were harvested from the Mid-Columbia Experiment Station, Hood River, Oregon, at 67 N firmness, stored at –1° or 20°C for 85 d and periodically tested for sensitivity to 0 or 500 µl l−1 propylene for at least 14 d at 20°C. Climacteric ethylene of pears stored at 20°C remained at low levels and started rising on the 90th day. Pears chilled at –1°C required 70 d to ripen and produced climacteric ethylene immediately upon transfer to 20°C. The sensitivity of the fruit to exogenous propylene increased progressively with storage time at –1°C. However, the non-chilled fruit responded to propylene similarly to freshly harvested fruit during the first 55 d of storage, then similarly to –1°C-stored fruit up to 85 d. Anjou pear ripening events and the sensitivity of the fruit to exogenous propylene developed differently in storage at non-chilling temperature compared with chilling temperature.

Chlorophyll fluorescence and anthocyanin content in chilled maize plants after return to a non- chilling temperature under various irradiances

The effect of irradiance on the ratio of variable to maximum fluorescence (Fv/Fm) and on the anthocyanin content of chilled (0.5 °C) young maize plants was investigated after returning the plants to a non-chilling temperature (25 °C). Compared to control plants grown throughout at 25 °C in the light, the Fv/Fm hardly changed during chilling or when returned to a non-chilling temperature in the dark, but there was a decrease in this parameter if the plants were shifted to the light after the cold treatment. Similarly, compared to the control plants there was no change in the anthocyanin content either at low temperature or after transfer to 25 °C in the dark. However, there was a sudden increase in the anthocyanin level after returning the plants from dark cold conditions to a non-chilling temperature in the light.

QUALITY OF PINK TOMATOES (cv. BUFFALO) AFTER STORAGE UNDER CONTROLLED ATMOSPHERE AT CHILLING AND NONCHILLING TEMPERATURES

ABSTRACTGreenhouse‐grown pink tomatoes (cv. Buffalo) were stored in air or in a controlled atmosphere (CA) of 4% O2 plus 2% CO2, to study the effect of CA at chilling and nonchilling temperatures on fruit quality characteristics. Tomatoes could be stored in CA at 12C for three weeks with no major changes in fruit appearance. CA was effective in delaying color development and ripening at this temperature. The soluble solids content was lower after CA storage, but no significant differences in firmness, pH or titratable acidity were observed between storage in air or CA. Storage in CA at 12C was also effective in reducing decay. However, at 6C, fruit showed high incidence of decay after both air and CA storage. CA did not alleviate chilling injury symptoms relative to air‐stored samples and may have caused CO2 injury. Water loss was greater under CA at both temperatures.

Effect of Non-Chilling Temperature and Light Intensity during Growth of Squash Cotyledons on the Composition of Thylakoid Membrane Lipids and Fatty Acids

The lipid composition, in particular the content of fatty acids in phosphatidylglycerol (PG), is believed to be crucial for the understanding of the chilling injury mechanism occurring in the thylakoid membrane (TM) of higher plants. In this investigation, we have studied the effect of growth conditions (e.g. temperature and light) on the composition of glycerolipid classes and their respective fatty acids during the maturation period of squash cotyledons. We have found that the changes in the lipid fatty acid composition of TM which are induced by different temperature and light growth conditions occurred only during the development of cotyledons but not when these latter had reached their maturity. The major changes were an increase of 18:3 and a decrease of 16:0 in galacto- and sulfolipids, and an increase of 16:1(3t) and 18:3 with a concomitant decrease of 16:0 and 18:1 in PG, when the temperature was low (20°C compared to 30°C). We conclude that low temperature conditions of growth induced an increase of the end acyl products [18:3 and/or 16:1(3t)] in PG and galactolipids. The possible mechanism is discussed in terms of the relative temperature dependence of fatty acid synthesis and desaturation processes. The light intensity of growth affected only the fatty acid composition of PG, i.e. when it was high (350 compare to 100 μmol m−2 s−1), an increase of 16:1(3t) at the expense of 16:0 was observed. Whatever the growth conditions, the level of 16:1(3t) increased during the maturation of cotyledons and was characterized by an increasing linear correlation (r=0.99) with the fresh weight. In contrast, a decreasing linear relationship (r=–0.99) was found between the fresh weight and 16:0. Thus, we propose that a constant level of 16:1(3t) is a good criterion for defining the chloroplast maturity and that it is highly advisable to study the effect of temperature and light on the lipid composition when the cotyledons have reached their maturity. Under these conditions, these effects can be considered regardless of developmental factors.

Superficial Scald Development on Apples at Chilling and Nonchilling Temperatures

`Cortland' and `Delicious' apples were stored at 0C for up to 25 weeks, and at 20C in either open boxes or non-sealed poly bags for up to 8 weeks. At 20C, lesions occurred mostly around lenticels, but with some calyx bronzing and scald-like symptoms on shaded areas. At 0C, typical scald symptoms occurred. At both temperatures, high concentrations of alpha-farnesene and conjugated trienes occurred in conjunction with symptom appearance, and both these concentrations and discolorations decreased with later harvest of fruit. Scald development appeared to be chilling-enhanced, but not chilling-dependent.

Postharvest changes in total soluble solids and tissue pH of cherimoya fruit stored at chilling and non-chilling temperatures

SummaryTotal soluble solids (TSS) and pH were determined in cherimoya fruit (Annona cher- imola Mill.) stored at several temperatures. TSS increased from about 8.3° Brix to 22° Brix during 4 d of ripening at 22°C. At the same time fruit pulp pH declined from 6.2 to 4.3. Similar values in TSS and pH, were not reached until the tenth day at 12°C. Fruit stored at 4°C underwent a slower increase in TSS and the decrease in pH was less than 1 unit. Storage at 1°C for 27 d did not modify pH, and TSS increased by only 2° Brix. Chilling injury was dependent on the length and temperature of storage. Fruit rewarmed to 22°C after storage for 11 d at 4°C underwent changes in TSS and pH similar to those found in fruit placed directly into 22°C air; on the contrary, pH was not modified when the chilling storage was for 15 d. However, rewarming of fruit previously stored at 1°C resulted in a slight increase in TSS and little change in pH.

Postharvest Changes of Sugar Concentrations in Chilled-Injured Cherimoya ( Annona cherimola Mill.)

Starch is the main form of carbon stores in cherimoya ( Annona cherimola Mill. cv. Fino de Jete ), constituting 10% to 12% of the fresh weight of mature-green cherimoya. During ripening starch was completely hydrolyzed when fruits were stored at non-chilling temperatures (22 °C or 12 °C), being mainly converted to glucose and fructose in equimolar concentrations, with transient accumulation of sucrose. Storage at chilling temperatures (4 °C or 1 °C) produced a decrease in the starch hydrolysis rate and consequently in the concentration of monosaccharides. When chilled-injured cherimoya were rewarmed to 22 °C after 11 days of storage in the chilling conditions, an activation of starch hydrolysis took place. In these rewarmed fruit, accumulation of glucose and fructose was smaller than in non chilling fruit. The final monosaccharide concentrations were dependent on the severity of the chilling-injury.

Antioxidants and Photosynthesis in the Leaves of Triticum durum L. Seedlings Acclimated to Low, Non-Chilling Temperature

The foliar antioxidant status and the photosynthetic capacity were compared in leaves of Triticum durum cv. Duilio seedlings grown under low light at an optimal temperature of 25°C or at a suboptimal, non-chilling temperature of 10°C. The leaves grown at 10°C did not show the responses commonly observed in cold-unhardened plants exposed to chilling- and chilling/light stress, such as reductions of leaf dry weight, net photosynthesis, photon yield and stomatal conductance to CO 2 transport and uptake. The main chlorophyll fluorescence characteristics suggested that photoinhibition of photosynthesis was not likely to occur under the adopted low temperature and light conditions. There was no evidence of oxidative stress and/or damage in leaves grown at 10°C, as judged by measuring superoxide dismutase, catalase and peroxidase activities, malondihaldehyde contents and foliar electrolyte retention capacity. Nevertheless, growth at low temperature almost tripled the amount of chlorophylls and carotenoids present, and induced significant increases in the foliar pools of ascorbic acid and glutathione. These changes could be regarded as preparatory adjustments aimed to anticipate a possible enhanced requirement of pigments and antioxidants in case of cold-induced oxidative stress and damage.

Lipid changes in microsomes and crude plastid fractions during storage of tomato frutis at chilling and nonchilling temperatures

Mature-green tomato fruits ( Lycopersicon esculentum) were stored for four or 12 days at chilling (2°) or nonchilling (15°) temperature. Fruits stored for 12 days at 15° ripened to the turning stage, whereas fruits at 2° did not ripen. Lipids of plastid and microsomal membrane fractions from pericarp tissue were analysed at harvest and after four or 12 days of storage. After 12 days at either 15° or 2°, the ratio of phospholipids (PL) to protein in microsomes declined, with a concomitant increase in the ratios of total membrane sterols (TMS) and cerebrosides (CB) to PL. The TMS:PL and CB:PL ratios also increased in crude plastid fractions. In both microsomes and plastids, free sterols (FS) increased more at 2° than at 15°, and hence accounted for a larger percentage of the TMS (FS + acylated steryl glycosides + steryl glycosides). The ratio of stigmasterol to sitosterol in all steryl lipids, but particularly in FS, increased more at 15° than at 2°. The unsaturation index of fatty acids in PL and galactolipids generally increased slightly during storage at both 15° and 2°. The ratio of phosphatidylethanolamine to phosphatidylcholine increased in both membrane fractions at both temperatures. In plastids, the ratio of mono- to digalactosyldiacylglycerols declined substantially at 2° but not at 15°.

Changes in galactolipid and phospholipid levels of tomato fruits stored at chilling and nonchilling temperatures

Mature-green stage two (MG2) and mature-green four to breaker-stage (MG4/BK) tomato ( Lycopersicon esculentum) fruits (harvested 30 and 36 days postanthesis, respectively) were stored at chilling (2°) or nonchilling (15°) temperature for zero, four or 12 days. Lipids extracted from pericarp tissue were analysed for mono- and digalactosyldiacylglycerols (MGDG and DGDG) and total phospholipids (PL). Results were similar for MG2 and MG4/BK fruits. At 2°, PL increased ≈ 7–11% during the first four days in storage, declining slightly by day 12. In contrast, PL declined ≈ 10–15% during storage at 15°, mostly over the first four days. Total galactolipids (GL) declined at both 2° and 15°, but losses were greater (≈ 25–35%) at 15°. Loss of GL at 15° was more rapid for MG4/BK compared with MG2 fruits, reflecting the more advanced stages of ripening after four and 12 days of storage. The ratio of MGDG to DGDG had dropped after 12 days at either 2° or 15°. The decline was greatest (from ≈ 1.8:1 to 1.2:1) in MG4/BK fruit stored at 15°, which had ripened to the pink stage. These results conflict with a recent report that loss of MGDG is associated with chilling, but not with ripening, of tomato fruits.

LIPID CHANGES IN MICROSOMES AND PLASTIDS DURING STORAGE OF TOMATO FRUIT AT CHILLING AND NONCHILLING TEMPERATURES

MG tomato fruit were stored for four or 12 days at chilling (2C) or nonchilling (15C) temperature. Fruits stored 12 days at 15C ripened to the turning stage, whereas fruits at 2C did not ripen. Lipids of microsomes and plastids from pericarp tissue were analyzed at harvest and after four or 12 days of storage. After 12 days at either 15C or 2C, the ratio of phospholipid (PL) to protein in microsomes declined, with a concomitant increase in the ratio of total membrane sterols (TMS) to PL. The TMS/PL ratio also increased in crude plastids. In both microsomes and plastids, free sterols (FS) increased more at 2C than at 15C, and thus accounted for a larger percentage of the TMS. The ratio of stigmasterol to sitosterol in steryl lipids, particularly in FS, increased more at 15C than at 2C. The unsaturation index of fatty acids in PL and galactolipids generally increased slightly during storage at both 15C and 2C. The ratio of phosphatidylethanolamine to P-choline increased in both membrane fractions at both temperatures. In plastids, the ratio of mono- to digalactosyldiacylglycerol declined substantially at 2C but not at 15C.