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At least 19 recordsLinked to original sources
PubMed2002

Microbial profile and antibiotic susceptibility of Campylobacter spp. and Salmonella spp. in broilers processed in air-chilled and immersion-chilled environments.

Carcass chilling is considered a critical step for inhibiting bacterial growth during poultry processing. The objective of this study was to compare microbiological loads and the incidence of Salmonella spp. and Campylobacter spp. on broiler carcasses subjected to immersion chilling and air chilling. Additionally, the antibiotic resistance patterns of pathogen isolates were determined. The results of this study indicated that the incidence of Salmonella spp. and Campylobacter spp. tends to be significantly lower in air-chilled broilers, suggesting that cross-contamination may be more prevalent for immersion-chilled broilers. No significant differences were detected between chilling treatments for total aerobic populations or for generic E. coli or coliform counts. Psychrotrophic populations were significantly larger (P < 0.05) in immersion-chilled broilers than in their air-chilled counterparts. Campylobacter isolates from immersion-chilled broilers had a higher incidence of resistance to nalidixic acid (NAL) and related fluoroquinolones than isolates from air-chilled broilers did. Additionally, Campylobacter isolates from air-chilled broilers had a higher frequency of resistance to tetracycline than isolates from immersion-chilled broilers did. With regard to Salmonella, isolates from immersion-chilled broilers had a higher incidence of resistance to NAL than isolates from air-chilled samples did. No Salmonella isolates from immersion- or air-chilled broilers were resistant to the fluoroquinolones tested. The chilling method used during processing may influence the microbial profile of postchilled broilers.

Adaptation, Physiological↗
PubMed1977

Effect of Light and Chilling Temperatures on Chilling-sensitive and Chilling-resistant Plants. Pretreatment of Cucumber and Spinach Thylakoids in Vivo and in Vitro.

The effects of chilling temperatures, in light or dark, on the isolated thylakoids and leaf discs of cucumber (Cucumis sativa L. "Marketer") and spinach (Spinacia oleracea L. "Bloomsdale") were studied. The pretreatment of isolated thylakoids and leaf discs at 4 C in the dark did not affect the phenazine methosulfate-dependent phosphorylation, proton uptake, osmotic response to sucrose, Ca(2+)-dependent ATPase activity, or chlorophyll content. Exposure of cucumber cotyledon discs and isolated thylakoids of cucumber and spinach to 4 C in light resulted in a rapid inactivation of the thylakoids. The sequence of activities or components lost during inactivation (starting with the most sensitive) are: phenazine methosulfate-dependent cyclic phosphorylation, proton uptake, osmotic response to sucrose, Ca(2+)-dependent ATPase activity, and chlorophyll. The rate of loss of proton uptake, osmotic response to sucrose, Ca(2+)-dependent ATPase activity and chlorophyll is similar for isolated cucumber and spinach thylakoids, whereas spinach thylakoids are more resistant to the loss of phenazine methosulfate-dependent phosphorylation. The thylakoids of spinach leaf discs were unaffected by exposure to 4 C in light. The results question whether the extreme resistance of spinach thylakoids treated in vivo is solely a function of the chloroplast thylakoid membranes and establish the validity of using in vitro results to make inferences about cucumber thylakoids treated in vivo at 4 C in light.

Journal Article↗
PubMed1994

Differential Gene Expression in Chilling-Acclimated Maize Seedlings and Evidence for the Involvement of Abscisic Acid in Chilling Tolerance.

An acclimation phenomenon was characterized in seedlings of chilling-sensitive maize (Zea mays L.) inbred G50 (Pioneer). Seedlings were germinated at 27[deg]C for 3 d and then exposed to chilling treatments of 4, 5, or 6[deg]C for 2, 4, 7, or 10 d in darkness. Damage symptoms in the more severe treatments included a waterlogged appearance and a discoloration of the tissue. The symptoms were most obvious in the mesocotyl. After a 10-d grow-out period in the greenhouse, moderately damaged seedlings exhibited chlorotic areas, an occasional disruption in leaf expansion, and a constriction of the mesocotyl. Growth and survival were improved by first exposing seedlings to a 14[deg]C acclimation treatment for 3 d before applying the chilling treatment. After chilling at 5[deg]C for 7 d, 79% of the acclimated seedlings survived, whereas only 22% of the nonacclimated seedlings survived. Differences in gene expression between acclimated and control seedlings were investigated using subtraction and differential screening techniques. Transcripts corresponding to three genes, car333, car30, and car757 (chilling acclimation responsive), were present in higher levels in seedlings after acclimation. Sequence analysis identified car333 as cat3, which encodes maize mitochondrial catalase isozyme 3. Characterization of these three clones revealed that all corresponding transcripts were elevated in acclimated seedlings in a manner that depended on the organ, i.e. coleoptile, mesocotyl, or root. Although transcripts were elevated in all three organs in response to acclimation, car30 was most abundant in the coleoptile and root, whereas cat3 and car757 were most abundant in the coleoptile and mesocotyl. Catalase activity followed the same general trend as cat3 transcript levels. Exogenous treatment with abscisic acid (ABA) resulted in an improvement in growth and survival of nonacclimated, chilled seedlings. Inhibition of ABA biosynthesis with fluridone abolished acclimation-induced chilling tolerance, and exogenous application of ABA to fluridone-treated seedlings restored chilling tolerance. Exogenous ABA treatment also resulted in increases in cat3, car30, and car757 transcript levels and catalase activity in the same organ-specific manner as in acclimated seedlings. These results indicate that ABA synthesis is essential for chilling tolerance. However, measurement of ABA levels in mesocotyls during acclimation and chilling revealed only a marginal increase during acclimation and a dramatic increase during chilling, regardless of whether or not seedlings were acclimated. Thus, although ABA may be required for chilling tolerance, we have no conclusive evidence that the acclimation process is mediated by ABA.

Journal Article↗
PubMed2000

The electron partitioning between the cytochrome and alternative respiratory pathways during chilling recovery in two cultivars of maize differing in chilling sensitivity.

Chilling effects on respiration during the recovery period were studied in two maize (Zea mays L.) cultivars differing in their tolerance to chilling: Penjalinan, a chilling-sensitive cultivar, and Z7, a chilling-tolerant cultivar. Both cultivars were exposed to 5 degrees C for 5 d, after which measurements were taken at 25 degrees C. Chlorophyll fluorescence analysis in dark-adapted leaves showed less damage in cv Z7 than in cv Penjalinan during recovery from the chilling treatment. Studies of the electron partitioning between the cytochrome and the alternative respiratory pathways during chilling recovery using the oxygen isotope fractionation technique showed that, although total leaf respiration was not affected by the chilling treatment in either of the two cultivars, electron partitioning to the alternative pathway was significantly increased in the more stressed chilling-sensitive cv Penjalinan, suggesting that increased activity of the alternative pathway is not related to the plant tolerance to chilling. These results suggest a possible role of the alternative pathway in plants under stress rather than specifically contributing to plant resistance to chilling.

Cell Respiration↗
PubMed1997

Effects of post-mortem time before chilling and chilling temperatures on water-holding capacity and texture of turkey breast muscle.

Two studies were conducted to determine 1) the effect of post-mortem time before chilling on hot boned prerigor breast muscle water-holding capacity (WHC), and 2) post-mortem temperature effect on sarcomere length and drip loss of uncooked breast, and shear force and WHC of turkey breast muscle that is hot-boned, marinated, and cooked. In Study 1, the turkey breast muscle was excised immediately after slaughter and chilled at 0 C. The effect of post-mortem time (15, 30, 45, 60, 90, and 120 min) before chilling on muscle pH, drip loss, and WHC (measured by homogenate cooking yield) was determined. In Study 2, hot boned prerigor breast slices were held at either 0 or 12 C and then at 3 h post-mortem stored at 2 C. Sarcomere length and drip loss of uncooked breast, and the shear force and WHC (measured by cooking yield) of cooked breast muscles with water, salt, and sodium tripolyphosphate were determined. Results indicated that pH on Day 1 post-mortem and cooking yield of water homogenates were not influenced by the post-mortem time before chilling. Drip losses increased as the post-mortem time before chilling was increased. Cooking yield of homogenate with water, salt, and sodium tripolyphosphate was decreased when breast muscle was chilled after 60 min post-mortem. Drip loss of breast was less at 0 C than at 12 C, but cooking yield and shear force were not affected by post-mortem chilling temperature. It was concluded that the post-mortem time before chilling has an influence on uncooked and cooked muscle WHC, but the differences found in uncooked muscle drip loss were not reflected in WHC or shear force of cooked muscle with water, salt, and sodium tripolyphosphate added.

Animals↗
PubMed1977

Temperature-induced Changes in Hill Activity of Chloroplasts Isolated from Chilling-sensitive and Chilling-resistant Plants.

The effect of temperature on Hill activity has been compared in chilling-sensitive and chilling-resistant plants. The Arrhenius activation energy (Ea) for the photoreduction of 2,6-dichlorophenolindophenol by chloroplasts isolated from two chilling-sensitive plants, mung bean (Vigna radiata L. var. Mungo) and maize (Zea mays L. cv. PX 616), increased at low temperatures, below 17 C for mung bean and below 11 C for maize. However, the Ea for this reaction in pea (Pisum sativum L. cv. Massay Gem), a chilling-resistant plant, likewise increased at temperatures below 14 C. A second change in Ea occurred at higher temperatures. The Ea decreased above about 28 C for mung bean, 30 C for maize, and 25 C for pea. At temperatures approaching 40 C, thermal inactivation of Hill activity occurred. These results, when taken together with previous results obtained with the chilling-resistant plant barley, indicate that chloroplasts from both chilling-sensitive and chilling-resistant plants can undergo a change in chloroplast membrane activity at low temperatures above freezing and that the presence of such a change in chloroplast membranes is not necessarily correlated with chilling sensitivity.

Journal Article↗
PubMed1981

Chilling Susceptibility of the Blue-green Alga Anacystis nidulans: II. STIMULATION OF THE PASSIVE PERMEABILITY OF CYTOPLASMIC MEMBRANE AT CHILLING TEMPERATURES.

Potassium ions and amino acids were found to leak from the cytoplasm to the outer medium when the blue-green alga, Anacystis nidulans, was exposed to the chilling temperatures. The leakage was marked below the critical temperature regions, the midpoint values for which were around 5 and 14 C in cells grown at 28 and 38 C, respectively. These temperature regions coincided with those critical for the susceptibility of the photosynthetic activities and the carotenoid absorption spectrum previously studied (Ono TA, N Murata 1981 Plant Physiol 67: 176-181).Potassium and magnesium ions in the cell suspension medium protected the algal cells from the chilling-induced damage of the Hill reaction with 1,4-benzoquinone. The activity of the Hill reaction which had been diminished by the first chilling treatment in a low salt medium was restored by the second chilling treatment of a high salt medium. The chilling susceptibility of the Hill reaction could be attributed to the leakage of cations from the cytoplasm due to increased permeability of the cytoplasmic membrane at the chilling temperatures.A mechanism is proposed to interpret the chilling susceptibility of A. nidulans: (a) at chilling temperatures, the bilayer lipids of the cytoplasmic membrane are in the phase separation state; (b) ions and solutes having low molecular weights leak from the cytoplasm to the outer medium when the lipids of the cytoplasmic membrane are in the phase separation state; (c) decreases in the intracellular concentrations of ions and solutes degrade the physiological activities of the cells.

Journal Article↗
PubMed1987

Chilling-Enhanced Photooxidation : The Peroxidative Destruction of Lipids during Chilling Injury to Photosynthesis and Ultrastructure.

Chilling-induced photooxidation was studied in detached leaves of chilling-sensitive (CS) cucumber (Cucumis sativus L.) and chilling resistant (CR) pea (Pisum sativum L.). The rates of photosynthesis and respiration, measured as O(2) exchange, were found to be comparable in the two species over a temperature range of 5 to 35 degrees C. Chilling at 5 degrees C for 12 hours in high light (1000 microeinsteins per square meter per second) decreased CO(2) uptake 75% in detached pea leaves whereas CO(2) uptake by cucumber was reduced to zero within 2 hours. Respiration was unaffected in either species by the chilling and light treatment. Although ultrastructural alterations were apparent in chloroplasts of both species, cucumber's were affected sooner and more severely. The mechanism of photooxidative lipid peroxidation was investigated by following the production of ethane gas under a variety of conditions. Maximum ethane production occurred in the CS cucumber at low temperature (5 degrees C) and high light (1000 microeinsteins per square meter per second). Atrazine, an inhibitor of photosynthetic electron transport, almost completely halted this chilling- and light-induced ethane production. These data, taken with those reported in an accompanying article (RR Wise, AW Naylor 1986 Plant Physiol 83: 278-282) suggest that the superoxide anion radical is generated in cucumber chloroplasts (probably via a Mehler-type reaction) during chilling-enhanced photooxidation. Parallel experiments were conducted on pea, a CR species. Detached pea leaves could only be made to generate ethane in the cold and light if they were pretreated with the herbicide parquat, a known effector of O(2) (-) production. Even so, pea showed no lipid peroxidation for 6 hours, at which time ethane production began and was at a rate equal to that for the chilled and irradiated cucumber leaves. The results indicate that pea has an endogenous mechanism(s) for the removal of toxic oxygen species prior to lipid peroxidation. This mechanism breaks down in pea after 6 hours in the cold, light, and the presence of paraquat.

Journal Article↗
PubMed1984

Temperature-dependent phase behavior of phosphatidylglycerols from chilling-sensitive and chilling-resistant plants.

Seven major lipid classes were isolated from leaves of chilling-sensitive and chilling-resistant plants, and the temperature-dependent phase behaviors of their aqueous dispersions were studied by a fluorescence polarization method using trans-parinaric acid and its methyl ester. Phosphatidylglycerols from the chilling-sensitive plants went from the liquid crystalline state into the phase separation state at about 30 degrees C in 100 mm NaCl and at about 40 degrees C in 5 mm MgCl(2). In contrast, phosphatidylglycerols from the chilling-resistant plants went into the phase separation state at a much lower temperature. The other classes of lipids remained in the liquid crystalline state at all temperatures between 5 degrees C and 40 degrees C regardless of the chilling sensitivity of the plants, except sulfoquinovosyl diacylglycerol from sponge cucumber in which phase separation seemed to begin at about 15 degrees C. Compositions and positional distributions of fatty acids of the lipids suggest that the phosphatidylglycerols from the chilling-sensitive plants, but no other lipids, contained large proportions of molecular species which undergo phase transition at room temperature or above. The thermotropic phase behaviors and the fatty acid compositions suggest that, among the major lipid classes from leaves of the chilling-sensitive plants, only phosphatidylglycerol can induce a phase transition. Since a major part of this lipid in leaves originates from the chloroplasts, phase transition probably occurs in the chloroplast membranes.

Journal Article↗
PubMed2005

Effects of temperature during chilling and pre-chilling periods on diapause and post-diapause development in a katydid, Eobiana engelhardti subtropica.

In Eobiana engelhardti subtropica, early laid eggs reach the diapause stage in early autumn. For long periods before winter, the eggs are exposed to temperatures higher than their theoretical lower threshold for development. In contrast, late-laid eggs cannot reach their diapause stage before winter. Our study showed that E. e. subtropica copes with these difficulties via the thermal response involving embryonic diapause. In this katydid, the almost fully developed embryo undergoes an obligatory diapause. When diapause eggs were maintained at a temperature of 20 degrees C or higher, diapause persisted for a long time. Diapause was effectively terminated by temperatures ranging from 1 to 11 degrees C, and hatching occurred successfully at temperatures from 11 to 15 degrees C. In addition to the chilling temperature, pre-chilling temperature modified diapause intensity and hatching time. Diapause eggs hatched earlier after chilling when the pre-chilling temperature was lower, within a range of 14.5-25 degrees C. Thus, the low-temperature requirement for diapause termination prevents early laid eggs from untimely hatching in autumn, and low temperatures before and during winter decrease diapause intensity and shorten the hatching time in the following spring. When eggs were chilled before diapause, they tolerated chilling and averted diapause. Thus, even if eggs encounter low temperatures before diapause, they can hatch in the following spring.

Animals↗
PubMed1979

Assay of chilling injury in wild and domestic tomatoes based on photosystem activity of the chilled leaves.

Tomato leaves were detached and stored at 0 C for various periods of time. Chloroplasts were isolated from the leaves and their photoreductive activities were determined. Comparisons were made between two altitudinal forms of the wild tomato Lycopersicon hirsutum Humb. and Bonpl. (a tropical lowlands form and a highlands form adapted to growth at 3,100 meters), and two cultivars of the domestic tomato L. esculentum Mill. In each case the capacity of the isolated chloroplasts to photoreduce ferricyanide declined linearly with time of storage of the leaves at 0 C, but not at 10 C. This injury developed more slowly in the high altitudinal form of the wild tomato compared with the low altitudinal form and the two domestic cultivars indicating an enhanced resistance toward chilling injury in the tomato from 3,100 meters. Chloroplast activity declined in green tomato fruit held at 0 C, at about the same rate as in the chilled leaves.Measurements of photochemical activities in the isolated chloroplasts and in vivo measurements of cytochrome-554 photooxidation in chilled leaves showed that the site of action of the chilling effect was water donation to photosystem II.The chilling-induced impairment of photoreductive activity in chloroplasts provides a useful assay for detecting and measuring differences in the susceptibility of plants to chilling injury.

Journal Article↗
PubMed1987

Comparison of galactolipase activity and free fatty acid levels in chloroplasts of chill-sensitive and chill-resistant plants.

Galactolipase activity in chloroplasts of several chill-resistant plants was found to be very low [0.02-0.13 mumol free fatty acid (FFA) liberated min-1 mg protein-1] or not detected. The same phenomenon was observed for soybean and members of the Cucurbitaceae such as cucumber, pumpkin, melon and squash. Since, following cold storage of cucumber leaves, the levels of monogalactosyl-diacylglycerol and digalactosyl-diacylglycerol in chloroplasts decrease while those of FFA accumulate it seems likely that in these typical chill-sensitive plants galactolipase is present but inactivated during isolation procedure. The low galactolipase activity in chloroplasts was accompanied by a relatively low FFA content ranging from 0.05 mumol to 0.30 mumol FFA mg chlorophyll (Chl)-1. However, both pea and horse bean chloroplasts (with low galactolipase activity) exhibit about 0.45 mumol FFA mg Chl-1. Elevated galactolipase activity was observed in chloroplasts of most chill-sensitive species (ranging from 0.31 mumol to 1.32 mumol FFA liberated min-1 mg protein-1) as well as in chloroplasts from broad bean, a member of a chill-resistant species (1.26 mumol FFA liberated min-1 mg protein-1). In addition in this latter group of plants FFA level in chloroplasts often did not fit the galactolipase activity. The results suggest that there exists a tendency for chilling tolerance of plants to decrease both galactolipase activity and FFA level. However, in some plant species with elevated galactolipase activity the chloroplast FFA level does not correlate with enzyme activity.

Carboxylic Ester Hydrolases↗
PubMed2001

Increasing the glutathione content in a chilling-sensitive maize genotype using safeners increased protection against chilling-induced injury.

With the aim of analyzing their protective function against chilling-induced injury, the pools of glutathione and its precursors, cysteine (Cys) and gamma-glutamyl-Cys, were increased in the chilling-sensitive maize (Zea mays) inbred line Penjalinan using a combination of two herbicide safeners. Compared with the controls, the greatest increase in the pool size of the three thiols was detected in the shoots and roots when both safeners were applied at a concentration of 5 microM. This combination increased the relative protection from chilling from 50% to 75%. It is interesting that this increase in the total glutathione (TG) level was accompanied by a rise in glutathione reductase (GR; EC 1.6.4.2) activity. When the most effective safener combination was applied simultaneously with increasing concentrations of buthionine sulfoximine, a specific inhibitor of glutathione synthesis, the total gamma-glutamyl-Cys and TG contents and GR activity were decreased to very low levels and relative protection was lowered from 75% to 44%. During chilling, the ratio of reduced to oxidized thiols first decreased independently of the treatments, but increased again to the initial value in safener-treated seedlings after 7 d at 5 degrees C. Taking all results together resulted in a linear relationship between TG and GR and a biphasic relationship between relative protection and GR or TG, thus demonstrating the relevance of the glutathione levels in protecting maize against chilling-induced injury.

Adaptation, Physiological↗
PubMed2005

Gating of aquaporins by low temperature in roots of chilling-sensitive cucumber and chilling-tolerant figleaf gourd.

Effects of low temperature (8 degrees C) on the hydraulic conductivity of young roots of a chilling-sensitive (cucumber, Cucumis sativus L.) and a chilling-resistant (figleaf gourd, Cucurbita ficifolia Bouche) crop have been measured at the levels of whole root systems (root hydraulic conductivity, Lp(r)) and of individual cortical cells (cell hydraulic conductivity, Lp). Exposure of roots to low temperature (LRT) for up to 6 d caused a stronger suberization of the endodermis in cucumber compared with figleaf gourd, but no development of exodermal Casparian bands in either species. Changes in anatomy after 6 d of LRT treatment corresponded with a reduction in hydrostatic root Lp(r) of cucumber roots by a factor of 24, and by a factor of 2 in figleaf gourd. In figleaf gourd, there was a reduction only in hydrostatic Lp(r) but not in osmotic Lp(r) suggesting that the activity of water channels was not much affected by LRT treatment in this species. Changes in cell Lp in response to chilling and recovery were similar to the root levels, although they were more intense at the root level. Activation energies (E(a)) and Q10 of water flow as measured at the cell level were high in cucumber (E(a)=109+/-13 kJ mol(-1); Q(10)=4.8+/-0.7; n=6-10 cells), but small in figleaf gourd (E(a)=11+/-2 kJ mol(-1); Q10=1.2+/-0.1; n=6-10 cells). Roots of figleaf gourd recovered better from LRT treatment than those of cucumber. In figleaf gourd, recovery (at both the root and cell level) often resulted in Lp and Lp(r) values which were even bigger than the original, i.e. there was an overshoot in hydraulic conductivity. These effects were larger for osmotic (representing the cell-to-cell passage of water) than for hydrostatic Lp(r). After a short-term (1 d) exposure to 8 degrees C followed by 1 d at 20 degrees C, hydrostatic Lp(r) of cucumber nearly recovered and that of figleaf gourd still remained higher due to the overshoot. By contrast, osmotic Lp(r) and cell Lp in both species remained high by a factor of 3 compared with the control, possibly due to an increased activity of water channels. After preconditioning of roots at LRT, increased hydraulic conductivity was completely inhibited by HgCl2 at both the root and cell levels. Different from figleaf gourd, recovery from chilling was not complete in cucumber after longer exposure to LRT. It is concluded that at LRT, both changes in the activity of aquaporins (AQPs) and alterations of root anatomy determine the water uptake in both species. The high temperature dependence of cell Lp in cucumber suggests conformational changes of AQPs during LRT treatment which result in channel closure and in a strong gating of AQP activity by low temperature. This mechanism is thought to be different from that in figleaf gourd where AQPs reacted in the conventional way, i.e. low temperature affected the mobility of water molecules in AQPs rather than their open/closed state, and Q(10) was low.

Adaptation, Physiological↗
PubMed1995

A comparison of chilled cabbage leaves and chilled gelpaks in reducing breast engorgement.

This study compared the effectiveness of chilled green cabbage leaves and chilled gelpaks in reducing breast engorgement in postpartum mothers. Thirty-four lactating women with breast engorgement used chilled cabbage leaves on one breast and chilled gelpaks on the other for up to eight hours. Their pain levels were established pre-treatment and compared post-treatment for both conditions. There was no difference in the post-treatment ratings for the two treatments. Mothers reported a statistically significant drop in pain with both treatments; 68 percent obtained relief within one to two hours. The majority of mothers preferred the cabbage leaves.

Brassica↗
PubMed1993

Discrimination between chilling-sensitive and chilling-resistant plants based on measurements of free fatty acid accumulation and inactivation of oxygen evolution in aged chloroplasts.

The effect of aging of isolated chloroplasts of two chilling-sensitive (CS) and three chilling-resistant (CR) plants on the inactivation of oxygen evolution and accumulation of free fatty acids (FFA) was studied at 30 degrees C, pH 5.5 or 7.0, in the absence or presence of either sorbitol or NaCl. Considerable accumulation of FFA in aged chloroplasts of CS plants: bean and maize line F7-RpIII was accompanied by a marked inactivation of oxygen evolution. This relation was not, however, found in chloroplasts of CR species: pea, wheat and maize line EP1-RpI, in which the accumulation of FFA upon aging was very low whereas the decline of the rate of oxygen evolution was pronounced. In contrast to changes observed at pH 5.5, the inactivation of oxygen evolution in chloroplasts of CR species aged at pH 7.0 was dependent on the composition of the medium, especially in wheat chloroplasts. Thus, for the evaluation of chilling sensitivity based on the measurements of oxygen evolution activity solely, either aging of chloroplasts at pH 5.5 or possibly at pH 7.0 with NaCl included into the incubation medium may be recommended. It is concluded that determination of both the extent of FFA accumulation and inactivation of oxygen evolution in aged chloroplasts might be applied as chilling tolerance indexes.

Chloroplasts↗
PubMed1981

Temperature-induced leakage from chilling-sensitive and chilling-resistant plants.

Leakage rates were determined from leaf cells loaded with rubidium and [(3)H]leucine. There was a differential response between leucine and rubidium leakage depending upon the species used. The rate of leucine leakage shows a small decline below 5 C for two altitudinal variants of Lycopersicon hirsutum Humb. and Bonpl., whereas Lycopersicon esculentum L. showed a marked increase below 5 C. Rubidium showed a marked increase in leakage rate below 10 C with the altitudinal variants, with only a slight increase for the L. esculentum species. A rough relationship existed between rubidium leakage rate at 1 C and the altitude of origin of the L. hirsutum race, the low altitudinal forms having higher leakage rates than the higher altitudinal variants. The L. esculentum lines show a rubidium leakage response similar to that of the high altitude L. hirsutum variants. Higher leakage rates were obtained if the calcium concentration in the medium was less than 1 millimolar and upon addition of metabolic poisons and detergents.The results are consistent with the view that chilling injury causes changes in the membrane and that cell leakage is an early symptom of this change in some species. Some chilling-sensitive species have increased leakage within 1 hour of exposure to chilling temperature.

Journal Article↗
PubMed1994

Different sites of photodamage in chilling-sensitive (sorghum) and chilling-resistant (barley and wheat) plants.

The electron transport chain was affected to varying degrees by high light intensity at low temperature in different crop plants. The PS II was found to be the sensitive site while PS I showed very little change in its activity. Photoinhibition affected the oxidizing side of PS II in all three plants. However, the site of inhibition was different in chilling-sensitive and chilling-resistant plants. In sorghum, the water splitting reaction was damaged while in barley and wheat the damage occurred in the reaction centre itself. It appears that photoinhibition may affect different sites within the PS II in chilling-resistant and sensitive plants.

Cold Temperature↗