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PubMed1988

A Comparison of the Effects of Chilling on Leaf Gas Exchange in Pea (Pisum sativum L.) and Cucumber (Cucumis sativus L.).

The effects of chilling on the photosynthesis of a chilling-resistant species, pea (Pisum sativum L. cv Alaska) and a chilling-sensitive species, cucumber (Cucumis sativus L. cv Ashley) were compared in order to determine the differences in the photosynthetic chilling sensitivity of these two species. For these experiments, plants were chilled (5 degrees C) for different lengths of time in the dark or light. Following a 1 hour recovery period at 25 degrees C, photosynthetic activity was measured by gas exchange (CO(2) uptake and H(2)O release), quantum yield, and induced chlorophyll fluorescence. The results show that pea photosynthesis was largely unaffected by two consecutive nights of chilling in the dark, or by chilling during a complete light and dark cycle (15 hours/9 hours). Cucumber gas exchange was reduced by one night of chilling, but its quantum yield and variable fluorescence were unaffected by dark chilling. However, chilling cucumber in the light led to reduced CO(2) fixation, increased internal leaf CO(2) concentration, decreased quantum yield, and loss of variable fluorescence. These results indicate that chilling temperatures in conjunction with light damaged the light reactions of photosynthesis, while chilling in the dark did not.

Journal Article↗
PubMed1988

A Comparison of the Effects of Chilling on Thylakoid Electron Transfer in Pea (Pisum sativum L.) and Cucumber (Cucumis sativus L.).

Experiments comparing the photosynthetic responses of a chilling-resistant species (Pisum sativum L. cv Alaska) and a chilling-sensitive species (Cucumis sativus L. cv Ashley) have shown that cucumber photosynthesis is adversely affected by chilling temperatures in the light, while pea photosynthesis is not inhibited by chilling in the light. To further investigate the site of the differential response of these two species to chilling stress, thylakoid membranes were isolated under various conditions and rates of photosynthetic electron transfer were determined. Preliminary experiments revealed that the integrity of cucumber thylakoids from 25 degrees C-grown plants was affected by the isolation temperature; cucumber thylakoids isolated at 5 degrees C in 400 millimolar NaCl were uncoupled, while thylakoids isolated at room temperature in 400 millimolar NaCl were coupled, as determined by addition of gramicidin. The concentration of NaCl in the homogenization buffer was found to be a critical factor in the uncoupling of cucumber thylakoids at 5 degrees C. In contrast, pea thylakoid membranes were not influenced by isolation temperatures or NaCl concentrations. In a second set of experiments, thylakoid membranes were isolated from pea and cucumber plants at successive intervals during a whole-plant light period chilling stress (5 degrees C). During wholeplant chilling, thylakoids isolated from cucumber plants chilled in the light were uncoupled even when the membranes were isolated at warm temperatures. Pea thylakoids were not uncoupled by the whole-plant chilling treatment. The difference in integrity of thylakoid membrane coupling following chilling in the light demonstrates a fundamental difference in photosynthetic function between these two species that may have some bearing on why pea is a chilling-resistant plant and cucumber is a chilling-sensitive plant.

Journal Article↗
PubMed2004

Reduction of dark chilling stress in N-fixing soybean by nitrate as indicated by chlorophyll a fluorescence kinetics.

Sub-optimal night temperatures below 15 degrees C (dark chilling) frequently reduce soybean [Glycine max (L.) Merrill] production. Nitrate application is known to alleviate some of the negative effects of low root zone temperatures, probably by counteracting the inhibition caused by decreased symbiotic nitrogen fixation (SNF). Under field conditions, however, dark chilling is frequently not accompanied by low root zone temperatures. The possibility that nitrate might increase dark-chilling tolerance under these conditions is still largely unexplored. In addition to quantifying vegetative development by means of the plastochron index, O-J-I-P (O-I(1)-I(2)-P) chlorophyll a fluorescence transients were recorded in soybean genotypes of contrasting chilling tolerance during and following exposure to dark chilling in the absence of low root zone temperatures. Plants, inoculated with the N(2)-fixing bacteria, Bradyrhizobium japonicum, were grown with and without nitrate supplementation. The recorded O-J-I-P chlorophyll a fluorescence transients were analysed by the so-called JIP-test which translates stress-induced alterations in these transients to changes in biophysical parameters that quantifies the energy flow through photosystem II (PSII). One of these parameters, the performance index (PI(ABS)), combines the three main functional steps (light energy absorption, excitation energy trapping, and conversion of excitation energy to electron transport) of photosynthetic activity by a PSII reaction centre complex into a single multiparametric expression. By using the PI(ABS) we could convincingly show that nitrate supplementation considerably enhances dark-chilling tolerance and recovery capacity of plants in the absence of low root zone temperatures. This was especially true for the chilling-sensitive genotype ('Java 29'), suggesting that the response of SNF to dark chilling might be an important factor contributing towards genotypic differences in chilling tolerance. Our results corroborated previous reports about the superior chilling tolerance of 'Maple Arrow', a chilling-tolerant genotype. The results obtained indicated that the PI(ABS) is a far more sensitive indicator of dark-chilling stress than the maximum quantum yield of primary photochemistry (F(V)/F(M)).

Journal Article↗
PubMed2003

Reduction of bacteria on pork carcasses associated with chilling method.

In addition to reducing the temperature of pork carcasses immediately after slaughter and before fabrication, blast chilling (snap chill) or conventional chilling can reduce bacterial populations associated with fresh meats. However, there is little information on bacteria survival resulting from the freeze or chill injury of meat products. In this study, porcine fecal slurries with and without pathogens (Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli) were inoculated onto skin-on and skin-off pork surfaces and subjected to industry-specific blast or conventional chilling conditions. A thin agar layer method was used for the recovery of freeze- or chill-injured cells. Test results indicated that there were no statistically significant (P > 0.05) differences between blast and conventional chilling treatments with respect to the reduction of high and low inoculation levels of mesophilic aerobic bacteria, total coliforms, or Escherichia coli on either skin-on or skin-off surfaces. Chilling treatments did not differ significantly (P > 0.05) with respect to their ability to reduce low (3 log10 CFU/cm2) levels of L. monocytogenes and Salmonella Typhimurium. However, C. coli was reduced to undetectable levels, even after enrichment, on pork surfaces inoculated with low levels (3 log10 CFU/cm2) and subjected to blast chilling. Blast and conventional chilling treatments were more effective against all pathogenic bacterial populations when pork surfaces where inoculated at high levels (5 log10 CFU/cm2). The effects of chilling techniques on microbial populations could provide pork processors with an additional intervention for pork slaughter or information to modify and/or improve the chilling process. The information obtained from this study has the potential to serve as a means of producing a microbiologically safer product.

Abattoirs↗
PubMed2004

Sensitivity to chilling of medaka (Oryzias latipes) embryos at various developmental stages.

As an essential step toward cryopreservation of fish embryos, we examined the chilling sensitivity of medaka (Oryzias latipes) embryos at various developmental stages. Embryos at the 2-4 cell, 8-16 cell, morula, blastula, and early gastrula stages were suspended in Hanks solution. They were chilled to various temperatures (usually 0 degrees C), kept for various periods (usually 20 min), then cultured for up to 14 d to determine survival (assessed by the ability to hatch). Embryos at the 2-4 cell stage were the most sensitive to chilling to 0 degrees C, but sensitivity decreased as development proceeded. The survival rate of 2-4 cell embryos was affected after 2 min of chilling at 0 degrees C; although the rate decreased gradually as the duration of chilling increased, 38% of them still survived after 40 min of chilling. Embryos at the 2-4 cell stage were sensitive to chilling at 0 or -5 degrees C, but much less sensitive at 5 or 10 degrees C. The survival rate of 2-4 cell embryos subjected to repeated rapid cooling and warming was similar to that of those kept chilled. When early gastrula embryos were preserved at 0 or 5 degrees C, the hatching rate did not decrease after 12 and 24h of chilling, respectively, but then decreased gradually as storage was prolonged; however, 3-10% of the embryos hatched even after storage for 10 d. In conclusion, although later-stage medaka embryos would be suitable for cryopreservation (from the perspective of chilling sensitivity), chilling injury may not be serious in earlier stage embryos.

Animals↗
PubMed1999

The effect of evaporative air chilling and storage temperature on quality and shelf life of fresh chicken carcasses.

The effect of evaporative air chilling on quality of fresh chicken carcasses was compared with air chilling as reference method. Cooling efficiency and total heat loss were significantly higher for evaporative air chilling. The chilling method was of great importance for weight loss. Chicken chilled in cold air lost considerably more weight than chicken cooled by evaporative air chilling; the difference was 1.8%. The chilling method also affected the skin color and the amount of moisture on skin surface. After evaporative air chilling, the chicken carcasses had a lighter color and more water on the back and under the wings. The moisture content in skin and meat, cooking loss, and pH were not affected by chilling method. Odor attributes of raw chicken and odor and flavor attributes of cooked chicken did not show any significant differences between the two chilling methods. The shelf life of chicken stored at 4 and -1 C were not affected significantly by chilling method. Storage time and temperature appeared to be the decisive factors for sensory and microbiological quality of fresh chicken carcasses.

Abattoirs↗
PubMed1994

Acclimation, Hydrogen Peroxide, and Abscisic Acid Protect Mitochondria against Irreversible Chilling Injury in Maize Seedlings.

Our previous results indicated that 3-d-old dark-grown chilling-sensitive maize (Zea mays L.) seedlings did not survive 7 d of 4[deg]C chilling stress, but 69% of them survived similar stress when the seedlings were either preexposed to 14[deg]C for 3 d or pretreated with 0.1 mM H2O2 for 4 h at 27[deg]C (T.K. Prasad, M.D. Anderson, B.A. Martin, C.R. Stewart [1994] Plant Cell 6: 65-74) or 1 mM abscisic acid (ABA) for 24 h at 27[deg]C (M.D. Anderson, T.K. Prasad, B.A. Martin, C.R. Stewart [1994] Plant Physiol 105: 331-339). We discovered that chilling imposed oxidative stress on the seedlings. Since H2O2 accumulated during the periods of both acclimation and nonacclimation, we concluded that H2O2 had dual effects at low temperature: (a) During acclimation, its early transient accumulation signals the induction of antioxidant enzymes such as catalase 3 and peroxidase to scavenge H2O2; and (b) at 4[deg]C in nonacclimated seedlings, it accumulates to damaging levels in the tissues because of low levels of these and perhaps other antioxidant enzymes. Three-day-old seedlings pretreated with H2O2 (a mild oxidative stress) or ABA showed induced chilling tolerance. In the present study, we investigated whether mitochondria are a target for chilling-induced oxidative stress and, if so, what differences do acclimation, H2O2, or ABA make to protect mitochondria from irreversible chilling injury. The results indicated that chilling, in general, impairs respiratory activity, the cytochrome pathway of electron transport, and ATPase activity regardless of the treatment. In pretreated seedlings, the activities of catalase 3 and peroxidase in the mitochondria increased severalfold compared with control and nonacclimated seedlings. The increases in these antioxidant enzymes imply that mitochondria are under oxidative stress and such increases could initiate a protective mechanism in the mitochondria. Mitochondrial respiration is partially cyanide resistant during chilling stress and also after the 1st d of recovery. Upon further recovery over 3 d, in contrast to nonacclimated seedlings, the mitochondria of acclimation-, H2O2-, and ABA-treated seedlings showed the following recovery features. (a) The mitochondrial respiration changed from a cyanide-resistant to a cyanide-sensitive cytochrome pathway, (b) cytochrome oxidase activity recovered to control levels, (c) the ability of mitochondria to generate ATP was regained, and (d) the antioxidant enzyme activities remained at or above control levels. Based on these results, we conclude that chilling impairs mitochondrial function and that chilling-induced oxidative stress seems to be a factor, at least in part, for causing possible irreversible damage to the mitochondrial membrance components. Acclimation, H2O2, and ABA provide a protective mechanism by inducing antioxidant enzymes to protect mitochondria from irreversible oxidative damage that is absent in nonacclimated seedlings. Therefore, we conclude that the ability of the seedlings to recover from chilling injury is, at least in part, due to the ability of the mitochondria to resume normal function.

Journal Article↗
PubMed2000

Involvement of polyamines in the chilling tolerance of cucumber cultivars.

The possible involvement of polyamines (PAs) in the chilling tolerance of cucumber (Cucumis sativus L. cv Jinchun No. 3 and cv Suyo) was investigated. Plants with the first expanded leaves were exposed to 3 degrees C or 15 degrees C in the dark for 24 h (chilling), and then transferred to 28 degrees C/22 degrees C under a 12-h photoperiod for another 24 h (rewarming). Chilling-tolerant cv Jinchun No. 3 showed a marked increase of free spermidine (Spd) in leaves, once during chilling and again during rewarming. Putrescine increased significantly during rewarming, but the increase of spermine was slight. Any of these PAs did not increase in chilling-sensitive cv Suyo during either period. PA-biosynthetic enzyme activities appear to mediate these differences between cultivars. Pretreatment of Spd to cv Suyo prevented chill-induced increases in the contents of hydrogen peroxide in leaves and activities of NADPH oxidases and NADPH-dependent superoxide generation in microsomes and alleviated chilling injury. Pretreatment of methylglyoxal-bis-(guanylhydrazone), a PA biosynthesis inhibitor, to chilled cv Jinchun No. 3 prevented Spd increase and enhanced microsomal NADPH oxidase activity and chilling injury. The results suggest that Spd plays important roles in chilling tolerance of cucumber, probably through prevention of chill-induced activation of NADPH oxidases in microsomes.

Adaptation, Physiological↗
PubMed1987

Chilling sensitivity of cucumber cotyledon protoplasts and seedlings.

Cucumber (Cucumis sativus L.) seedlings are more sensitive to chilling stress when transferred to low temperature from the night cycle than from the day cycle. However, greater damage occurs when chilling is carried out in light than in dark. Freshly isolated protoplasts are extremely sensitive to damage when chilled at 4 degrees C in light, but suffer significantly less injury when chilled in dark. If freshly isolated protoplasts are pre-chill conditioned at 27 degrees C in either light or dark for a few hours prior to exposure to various chilling stresses, subsequent chilling damage is markedly reduced. Damage to chilled protoplasts also is reduced if cultures are placed in dark instead of light immediately following removal from low temperature. Experiments utilizing the cell wall synthesis inhibitor, dichlorobenzonitrile, showed that cell wall regeneration during the pre-chill conditioning period at 27 degrees C does not appear to be associated with the enhanced chilling tolerance observed in these cultures. The results obtained in this investigation suggest that the physiological properties of cucumber cotyledon protoplasts accurately reflect those of intact seedlings, and hence provide a good system for studies into the mechanism of chilling damage in plants.

Journal Article↗
PubMed1989

Photoinhibition at low temperature in chilling-sensitive and -resistant plants.

Photoinhibition resulting from exposure at 7 degrees C to a moderate photon flux density (300 micromoles per square meter per second, 400-700 nanometers) for 20 hours was measured in leaves of annual crops differing widely in chilling tolerance. The incidence of photoinhibition, determined as the decrease in the ratio of induced to total chlorophyll fluorescence emission at 693 nanometers (F(v)/F(max)) measured at 77 Kelvin, was not confined to chilling-sensitive species. The extent of photoinhibition in leaves of all chilling-resistant plants tested (barley [Hordeum vulgare L.], broad bean [Vicia faba L.], pea [Pisum sativum L.], and wheat [Triticum aestivum L.]) was about half of that measured in chilling-sensitive plants (bean [Phaseolus vulgaris L.], cucumber [Cucumis sativus L.], lablab [Lablab purpureus L.], maize [Zea mays L.], pearl millet [Pennisetum typhoides (Burm. f.) Stapf & Hubbard], pigeon pea [Cajanus cajun (L.) Millsp.], sesame [Sesamum indicum L.], sorghum [Sorghum bicolor L. Moench], and tomato [Lycopersicon esculentum Mill.]). Rice (Oryza sativa L.) leaves of the indica type were more susceptible to photoinhibition at 7 degrees C than leaves of the japonica type. Photoinhibition was dependent both on temperature and light, increasing nonlinearly with decreasing temperature and linearly with increasing light intensity. In contrast to photoinhibition during chilling, large differences, up to 166-fold, were found in the relative susceptibility of the different species to chilling injury in the dark. It was concluded that chilling temperatures increased the likelihood of photoinhibition in leaves of both chilling-sensitive and -resistant plants. Further, while the photoinhibition during chilling generally occurred more rapidly in chilling-sensitive plants, this was not related directly to chilling sensitivity.

Journal Article↗
PubMed1992

Effects of chlorination of chill water on the bacteriologic profile of raw chicken carcasses and giblets.

In March 1989, the USDA Food Safety and Inspection Service sampled raw chicken carcasses and giblets at a federally inspected slaughter establishment in Puerto Rico to determine the effects of adding chlorine to carcass and giblet chill water on bacterial contents of raw poultry products. Over four 8-hour workdays, 200 carcass rinse samples were collected at 3 sites in the establishment; 39 giblet rinse samples were collected at 1 site. Analyses of the carcass rinse samples indicated that carcasses had average aerobe plate counts of log10 3.20 before chilling and 2.51 after chilling; Enterobacteriaceae counts of log10 2.57 before chilling and 1.75 after chilling; and Escherichia coli counts of log10 2.04 before chilling and 1.20 after chilling. Salmonellae were found on 43% of the carcasses before chilling and on 46% after chilling. Analyses of the giblet and neck rinse samples indicated that raw giblets and necks after chilling had average aerobe plate count of log10 3.49, Enterobacteriaceae count of log10 2.57, and E coli count of log10 1.06. Salmonellae were found on 12% of the giblets and necks sampled. Results compared favorably with giblet and neck rinse sample results obtained during a baseline sampling study in November and December 1987. The baseline results indicated aerobe plate count of log10 3.72; Enterobacteriaceae count of log10 2.90; E coli count of log10 1.14; and salmonellae on 69% of the giblets and necks sampled. Placing raw chicken carcasses in chlorinated chill water reduced aerobe, Enterobacteriaceae, and E coli plate counts. Prevalence of carcasses with salmonellae remained nearly the same.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Light-dependent reversal of dark-chilling induced changes in chloroplast structure and arrangement of chlorophyll-protein complexes in bean thylakoid membranes.

Changes in chloroplast structure and rearrangement of chlorophyll-protein (CP) complexes were investigated in detached leaves of bean (Phaseolus vulgaris L. cv. Eureka), a chilling-sensitive plant, during 5-day dark-chilling at 1 degrees C and subsequent 3-h photoactivation under white light (200 mumol photons m(-2) s(-1)) at 22 degrees C. Although, no change in chlorophyll (Chl) content and Chl a/b ratio in all samples was observed, overall fluorescence intensity of fluorescence emission and excitation spectra of thylakoid membranes isolated from dark-chilled leaves decreased to about 50%, and remained after photoactivation at 70% of that of the control sample. Concomitantly, the ratio between fluorescence intensities of PSI and PSII (F736/F681) at 120 K increased 1.5-fold upon chilling, and was fully reversed after photoactivation. Moreover, chilling stress seems to induce a decrease of the relative contribution of LHCII fluorescence to the thylakoid emission spectra at 120 K, and an increase of that from LHCI and PSI, correlated with a decrease of stability of LHCI-PSI and LHCII trimers, shown by mild-denaturing electrophoresis. These effects were reversed to a large extent after photoactivation, with the exception of LHCII, which remained partly in the aggregated form. In view of these data, it is likely that dark-chilling stress induces partial disassembly of CP complexes, not completely restorable upon photoactivation. These data are further supported by confocal laser scanning fluorescence microscopy, which showed that regular grana arrangement observed in chloroplasts isolated from control leaves was destroyed by dark-chilling stress, and was partially reconstructed after photoactivation. In line with this, Chl a fluorescence spectra of leaf discs demonstrated that dark-chilling caused a decrease of the quantum yield PSII photochemistry (F(v)/F(m)) by almost 40% in 5 days. Complete restoration of the photochemical activity of PSII required 9 h post-chilling photoactivation, while only 3 h were needed to reconstruct thylakoid membrane organization and chloroplast structure. The latter demonstrated that the long-term dark-chilled bean leaves started to suffer from photoinhibition after transfer to moderate irradiance and temperature conditions, delaying the recovery of PSII photochemistry, independently of photo-induced reconstruction of PSII complexes.

Chloroplasts↗
PubMed2005

Differential response of photosynthesis in greenhouse- and field-ecotypes of tomato to long-term chilling under low light.

Three greenhouse- and four field-ecotype varieties of domestic tomato (Lycopersicon esculentum) were compared for the sensitivity of their photosynthetic apparatus to chilling under low light intensity. After chilling at 12/7 degrees C under 100 micromolm(-2)s(-1) of light for 10 days, they were allowed to recover at 25/18 degrees C and 600 micromolm(-2)s(-1) of light for 10 days. For both pre-chilling and recovered plants, greenhouse-ecotype varieties did not necessarily show higher net CO(2) assimilation rate (A), quantum yield of electron transport at PSII (Phi(PSII)) and photochemical quenching (q(P)) than field-ecotype varieties. However for the post-chilling period, greenhouse-ecotype varieties, exhibited higher A, and Phi(PSII) values than field-ecotype varieties. The difference in Phi(PSII) was found to be largely due to q(P). The absence of ecotypic differences in pre-chilling plants indicates that the trait was not expressed constitutively, but relied mainly on adaptation/acclimation mechanisms. Greenhouse-ecotype varieties were able to adapt to low temperature and low light more quickly, and then exhibited higher A, Phi(PSII), q(P) values and greater re-growth capacity after chilling than field-ecotype varieties. Plant re-growth capacity after chilling was highly correlated with Phi(PSII) and q(P) measured in chilled plants, suggesting the usefulness of Phi(PSII) and q(P) measured at low temperature after defined chilling stresses as screening indexes for chilling tolerance in breeding programs.

Acclimatization↗
PubMed2004

Gas Exchange and Co-regulation of Photochemical and Nonphotochemical Quenching in Bean during Chilling at Ambient and Elevated Carbon Dioxide.

The effects of elevated (700 micromol mol(-1)) and ambient (350 micromol mol(-1)) CO(2) on gas exchange parameters and chlorophyll fluorescence were measured on bean (Phaseolus vulgaris) during 24 h chilling treatments at 6.5 degrees C. Consistent with previous research on this cultivar, photosynthetic decline during chilling was not significantly affected by CO(2) while post-chilling recovery was more rapid at elevated compared to ambient CO(2). Our primary focus was whether there were also CO(2)-mediated differences in demand on nonphotochemical quenching (NPQ) processes during the chilling treatments. We found that photosystem II quantum yield and total NPQ were similar between the CO(2) treatments during chilling. In both CO(2) treatments, chilling caused a shift from total NPQ largely composed of q(E), the protective, rapidly responding component of NPQ, to total NPQ dominated by the more slowly relaxing q(I), related to both protective and damage processes. The switch from q(E) to q(I) during chilling was more pronounced in the elevated CO(2) plants. Using complementary plots of the quantum yields of photochemistry and NPQ we demonstrate that, despite CO(2) effects on the partitioning of NPQ into q(E) and q(I) during chilling, total NPQ was regulated at both CO(2) levels to maximize photochemical utilization of absorbed light energy and dissipate only that fraction of light energy that was in excess of the capacity of photosynthesis. Photodamage did occur during chilling but was repaired within 3 h recovery from chilling in both CO(2) treatments.

Journal Article↗
PubMed2002

Reduced chilling tolerance in elongating cucumber seedling radicles is related to their reduced antioxidant enzyme and DPPH-radical scavenging activity.

Cucumber seedling radicles become more chilling sensitive as they elongate. Chilling seedlings with radicles 20 mm long for 48 h at 2.5 degrees C inhibited subsequent growth by 36%, while it reduced the growth of 70 mm-long radicles by 63%. Although the growth rate of non-chilled cucumber radicles at 25 degrees C is constant from 20 to 80 mm, tissue viability [i.e. reduction of TTC (2,3,5-triphenyltetrazolium chloride) to formazan] and DPPH (alpha,alpha-diphenyl-beta-picrylhydrazyl) radical scavenging activity of apical tissue declines as radicles elongate from 20 to 80 mm in length. TTC reduction, DPPH-radical scavenging activity and protein content of apical tissue were higher in 20 than in 70 mm radicles immediately after chilling and after an additional 48 h of growth at 25 degrees C. Catalase (CAT; EC 1.11.1.6) and ascorbate peroxidase (APX; EC 1.11.1.11) activity was higher in the apical tissue of 20 than in 70 mm radicles before chilling. Immediately after chilling and after an additional 48 h at 25 degrees C, superoxide dismutase (SOD; EC 1.15.1.1), glutathione reductase (GR; EC 1.6.4.2), and guaiacol peroxidase (GPX; EC 1.11.1.7) activity increased more rapidly in 70 mm radicles than in 20 mm radicles (SOD, GR, and GPX activity in 70 mm radicles was 1.5-, 1.9- and 8.6-fold higher, respectively, than in 20 mm radicles). However, APX and CAT activity in 20 mm radicles were always higher than in 70 mm radicles. Growth after chilling enhanced the activity of all antioxidant enzymes compared to that found in non-chilled tissue; however, CAT activity in 70 mm radicles did not recover to levels found in non-chilled tissue. Higher levels of CAT, APX and DPPH-radical scavenging activity are correlated with higher chilling tolerance of 20 mm-long cucumber radicles compared to 70 mm-long radicles.

Journal Article↗
PubMed2006

Water relations and an expression analysis of plasma membrane intrinsic proteins in sensitive and tolerant rice during chilling and recovery.

A symptom of chilling injury is development of water deficit in shoots, resulting from an imbalance of water transport and transpiration. In this work, two rice varieties (Oryza sativa L. var. Wasetoitsu and Somewake) seedlings were chilled at 7 degrees C, followed by recovery at 28 degrees C. Based on the growth phenotype and electrolyte leakage tests, Somewake was shown to be a chilling-tolerant variety, and Wasetoitsu a chilling-sensitive one. The chilling stress reduced markedly the relative water content (RWC) of leaves, accumulative transpiration and osmotic root hydraulic conductivity (Lp) in both varieties. But when returned to 28 degrees C, the water relation balance of Somewake recovered better. The mRNA expression profile of all the 11 plasma membrane intrinsic proteins (PIPs), a subgroup of aquaporins, was subsequently determined by real-time reverse transcription (RT)-PCR with TaqMan-minor grove binder (MGB) probes derived from rice var. Nipponbare during chilling treatment and recovery. Most of the PIP genes was down-regulated at the low temperature, and recovered at the warm temperature. The relative expression of some PIPs in both Somewake and Wasetoitsu decreased in parallel during the chilling. However during the recovery, the relative expression of OsPIP1;1, OsPIP2;1, OsPIP2;7 in shoots and OsPIP1;1, OsPIP2;1 in roots were significantly higher in Somewake than Wasetoitsu. This supports the role of PIPs in re-establishing water balance after chilling conditions. We discuss the diversified roles played by members of the aquaporin PIP subfamily in plant chilling tolerance depending on aquaporin isoforms, plant tissue and the stage of chilling duration.

Aquaporins↗
PubMed2004

Dark chilling inhibition of photosynthesis and symbiotic nitrogen fixation in soybean during pod filling.

The growth stage of a soybean [Glycine max (L.) Merrill] plant may influence its physiological response to dark chilling. Opposed to vegetative development, the intense nutrient and energy requirements of the developing seeds during pod filling could cause additional chilling damage and decreased recovery capacity. Previously, we investigated dark chilling tolerance during vegetative development in two soybean genotypes, 'Maple Arrow' and 'Fiskeby V' and consistently found that photosynthesis and symbiotic nitrogen fixation (SNF) was less affected by dark chilling in 'Maple Arrow'. In this study we describe the dark chilling response of the same genotypes during pod filling. Our aim was to establish whether the potential selection criteria for dark chilling tolerance, identified during vegetative development, was equally sensitive during pod filling. The results indicate that photosynthesis is less affected by dark chilling in 'Maple Arrow' than in 'Fiskeby V', not only during vegetative development, but also during the critical reproductive stage of pod filling. 'Fiskeby V' also lacks the ability to restore normal photosynthetic capacity during an extended recovery treatment. The decrease of nodule ureide content indicates that SNF was inhibited to a similar extent in both genotypes. Nodule ureide content was reduced more than stem ureide content, suggesting that the former is a more sensitive indicator of chilling stress effects on SNF. The results indicate that certain photosynthetic and fluorescence parameters are sensitive indicators of dark chilling tolerance throughout plant development and should prove valuable in future breeding programmes aimed at increasing the chilling tolerance of soybean.

Carbon Dioxide↗
PubMed2002

The role of carcass chilling rate in the development of pale, exudative turkey pectoralis.

Pale, soft, and exudative meat is a growing problem in the turkey industry that has been associated with processing conditions such as improper chilling. This condition is caused by accelerated postmortem glycolysis while carcass temperatures are still elevated, resulting in protein denaturation and poor meat quality. To evaluate the involvement of chilling rate, 48 toms were conventionally processed at 17.5 wk of age and chilled at 0,10, 20, or 30 C for 45 or 90 min and deboned. Temperature and pH of the breast fillet were recorded at 15 min, deboning time, and at 24 h postmortem (PM). Drip loss, L* value, expressible moisture, gel strength, and cook loss were determined on the fillets at 24 h PM. At 15 min PM, there were no temperature differences among treatments. At deboning, the carcasses chilled at 30 C had the highest fillet temperature and had significantly lower pH values when compared to those chilled at 0 and 10 C. L* value was significantly higher in carcasses chilled at 30 C and deboned at 60 min PM when compared to 0 and 10 C chilled carcasses. There were no significant differences in L* values at 105 min and 24 h PM among any treatment group. Drip loss and cook loss were significantly higher in carcasses chilled at 30 C compared to the remaining treatments. There were no differences in expressible moisture at 60 or 105 min PM or gel strength at 60 min PM in any of the treatments. However, at 105 min PM, carcasses chiled at 0 C had higher gel strength when compared to the remaining treatments. These results indicate that there is a relationship between chilling rates and meat quality with slower chilling producing PSE-like characteristics.

Animals↗