Non-acclimated Ones Research Articles

An easy methodology for frost tolerance assessment in olive cultivars.

Olive cultivation, like other evergreen fruit crops worldwide, is limited by the occurrence of frost episodes in different times of the year, mainly in winter or early spring. Some contradictory results are reported about cultivars' response to frost, which depends on the physiological stage of the tissues (acclimated or not acclimated) when the cold or frost episode occurs. This work aimed to implement a user-friendly and reliable lab method for discerning frost tolerance. Our methodology considered both detached leaves and potted plantlets. The optimal temperature at which damage differentiated between cultivars was evaluated, as well as the time of exposure to cold and the recovery time for the correct evaluation of the symptoms. Furthermore, a comparative analysis of damage on both young and mature leaves was conducted. To validate the efficacy of the methodology, assessments were conducted on the cultivars 'Arbequina' (tolerant), 'Picual' (moderately tolerant), and 'Frantoio' (susceptible) under acclimated and non-acclimated conditions. The results indicated that, when detached leaves were used for frost evaluation, a temperature of -10°C ± 1°C for 30 min and a recovery time at 26°C for 24-48 h after exposure to cold are enough to induce damages on the leaves and discriminate between cultivar susceptibility. Under these conditions, a precise assessment of symptoms can be made, facilitating the categorization of frost tolerance level in various olive cultivars. Notably, no significant differences were observed between young and mature leaves during the evaluation process. On the other hand, the critical temperature to assess damages on potted plantlets was determined to be -7°C ± 1°C. In addition, it was observed that acclimated plants exhibited fewer symptoms compared to non-acclimated ones, with 'Frantoio' being the most affected alongside 'Picual' and 'Arbequina'. The implemented methodology will allow the assessment of frost tolerance in several olive cultivars within a short timeframe, and it is proven to be user-friendly and reliable.

Inhibitory effects of long chain fatty acids on anaerobic sludge treatment: Biomass adaptation and microbial community assessment

The study investigated the effects of long-chain fatty acids (LCFA) on anaerobic sludge treating lipid-rich wastewater. It involved batch experiments with three sludge samples: two acclimated to lipids and one non-acclimated. The experiments aimed to observe the degradation of LCFA, specifically oleate and palmitate, by dosing them at concentrations ranging from 50 to 600 mg/L. Measurements of the cumulative methane production and the LCFA concentration, quantified as fat, oil, and grease (FOG) were performed. To ensure the sludge was free from other biodegradable substrates, part of the samples was pre-incubated without feed. The tests were conducted with both pre-incubated and non-incubated inoculum sludge. The findings revealed that oleate was degraded more efficiently than palmitate across all sludge samples, with a greater conversion rate to methane. Sludge samples acclimated to lipids showed a superior capacity to degrade LCFA compared to non-acclimated ones. It was noted that at concentrations above 400 mg/L, the conversion of LCFAs to intermediate compounds was inhibited, although this did not affect the subsequent methane production. The study concludes with a recommendation for sludge adaptation strategies to boost the efficiency of anaerobic wastewater treatment systems dealing with lipid-rich waste. The presence of LCFA-degrading bacteria families like Kosmotogaceae, Petrotogaceae, and Synergistaceae in the acclimated sludge samples underscores the adaptation and potential for improved degradation performance.

PHOTOPROTECTIIVE STRATEGIES OF UNICELULAR RED ALGA RHODELLA VIOLACEA DURING ACCLIMATION TO STRONG LIGHT

Red algae contain in their photosynthetic machinery water-soluble antenna complexes - phycobilisomes (PBSs) attached to thylakoid membranes to transfer excitation energy to photosystems. Strong light absorbed by the PBSs triggers a fast formation of transthylakoid ΔpH that follows the non-photochemical quenching of chlorophyll (Chl) fluorescence. The ΔpH build-up seems to be essential for photoprotecting the photosynthetic apparatus in the absence of xanthophyll cycle common to higher plants. However, the photoprotective mechanisms of red algae are not studied in details yet. 
 We present here our research of the Chl fluorescence quenching in unicellular red algae Rhodella violacea and its correlation with the ΔpH gradient being formed. The relation of this phenomenon to photoprotection of photosystem 2 (PS 2) in the normal and high light-acclimated Rhodella cells is also examined. 
 Under the photoinhibitory conditions (white light of 2000-3000 μE/m2s), the ΔpH-dependent Chl fluorescence quenching was found to delay the kinetics of PS 2 photoinhibition. The uncouplers like nigericin and NH4Cl are known to break down ΔpH gradient, lead to the dissipation of Chl fluorescence quenching followed by enhancing the PS 2 photoinhibition rate. The same effect showed far-red (FR) light consuming transthylakoid ΔpH. ATPase inhibitor, DCCD, having no impact on ΔpH didn’t influence PS 2 photoinhibition as well this implies the photoprotection to be fulfilled by the proton gradient rather than by ATP synthesis. 
 Long-term acclimation of Rhodella cells to higher irradiances (500-1000 μE/m2s) results in a partial loss of the periphery phycoerythrin-containing subunits by PBSs. The light-acclimated cultures display a higher resistance to the photoinhibitory light than the non-acclimated ones. This could be explained by diminishing the energy transfer from the reduced PBSs to PS 2 as well as light screening by the secondary carotenoids synthesized during light exposure. 
 Data on low-temperature (77K) fluorescence allow to evaluate the molecular mechanisms of light-induced Chl fluorescence suppression in Rhodella cells and its recovery in darkness.

Heat Acclimation and Inhibition of Cytokinin Degradation Positively Affect Heat Stress Tolerance of Arabidopsis.

In order to pinpoint phytohormone changes associated with enhanced heat stress tolerance, the complex phytohormone profiles [cytokinins, auxin, abscisic acid (ABA), jasmonic acid (JA), salicylic acid and ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC)] were compared in Arabidopsis thaliana after direct heat shock (45°C, 3 h) and in heat-stressed pre-acclimated plants (1 h at 37°C followed by 2 h at optimal temperature 20°C). Organ-specific responses were followed in shoot apices, leaves, and roots immediately after heat shock and after 24-h recovery at 20°C. The stress strength was evaluated via membrane ion leakage and the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) and antioxidant enzymes [superoxide dismutases, guaiacol peroxidases (POD), catalases, ascorbate peroxidases (APX)]. Heat acclimation diminished negative effects of heat stress, especially in apices and roots, no significant differences being observed in leaves. Low NOX1-3 activities indicated diminished production of reactive oxygen species. Higher activity of APX, POD1, and the occurrence of POD3-4 reflected acclimation-stimulated readiness of the antioxidant system. Acclimation diminished heat shock-induced changes of ABA, JA, cytokinin, and auxin levels in apices. Excess of ABA catabolites suggested an early stress response. The strong up-regulation of ABA and ACC in roots indicated defense boost in roots of acclimated plants compared to the non-acclimated ones. To evaluate the possibility to enhance stress tolerance by cytokinin pool modulation, INCYDE-F, an inhibitor of cytokinin oxidase/dehydrogenase, was applied. As cytokinin effects on stress tolerance may depend on timing of their regulation, INCYDE was applied at several time-points. In combination with acclimation, INCYDE treatment had a slight positive effect on heat stress tolerance, mainly when applied after 2-h period of the optimal temperature. INCYDE increased contents of cytokinins trans-zeatin and cis-zeatin in roots and auxin in all tissues after heat shock. INCYDE also helped to suppress the content of ABA in leaves, and ethylene in apices and roots. INCYDE application to non-acclimated plants (applied before or after heat shock) strengthened negative stress effects, probably by delaying of the repair processes. In conclusion, pre-treatment with moderately elevated temperature enhanced heat stress tolerance and accelerated recovery after stress. Inhibition of cytokinin degradation by INCYDE slightly improved recovery of acclimated plants.

Effect of algae acclimation to the wastewater medium on the growth kinetics and nutrient removal capacity.

Algal treatment methods have been widely used in nutrient removal studies. However, in most cases, the experimental conditions have not been fully complied with actual conditions. For instance, the effect of algae acclimation to wastewater medium on cell growth and removal efficiency has generally been ignored in laboratory scale experiments. This paper investigates the effect of acclimation on cell growth and nutrient uptake rates of Arthrospira platensis and Chlorella vulgaris. For this purpose, batch reactors, which contained the synthetic secondary effluent, had been inoculated by acclimated algae cells and the growth parameters were measured daily, as well as nutrient concentration. A significant decrease (P < 0.05) in chlorophyll-a content of acclimated A. platensis was observed, although there was no significant change in specific growth rate (μ) and doubling time (dt), in comparison with the non-acclimated ones. Moreover, the acclimation process changed the chlorophyll-a content and kinetic parameters of Chlorella vulgaris. Furthermore, t test results showed a significant increase in removal rate of nitrogen compounds through the acclimation. Residence time of A. platensis and C. vulgaris was also reduced through the acclimation by approximately 50% and 25%, respectively.

High Light Acclimated Developing Primary Leaves of Wheat Seedlings Generate Signal for Stress Adaptation through Super Oxide Dismutase

Wheat seedlings grown in petri dishes were acclimated to high light during their development and subsequently were subjected to osmotic stress by application of polyethylene glycol (PEG). The photochemical efficiency of photosystem II (PS II) of the acclimated seedlings was found to be higher than that of non-acclimated ones under osmotic stress during senescence. The damage of the photosynthetic apparatus seems to be mediated by reactive oxygen species. The higher level of lutein (Lut) and superoxide dismutase (SOD) activity in acclimated seedlings suggest their involvement in the protective mechanism. The senescing leaves, although in a deteriorating phase, exhibit tolerance to osmotic stress due to the adaptation potential acquired earlier during high light (HL) acclimation.

Особенности белково-пептидного и углеводного состава супернатантов из личинок Tenebrio molitor

The paper describes the chromatographic studies on the molecular-mass distribution of proteins and peptides of supernatants, derived from Tenebrio molitor larvae during cold acclimation. Supernatants of non-acclimated larvae of T. molitor had the highest amount of peptide fractions. It has been shown that cold-acclimated T. molitor larvae comprised the low-molecular peptide fractions with MW of (540 ± 20) – (2.255 ± 85) Da, and high-molecular peptides with MW of (4.675 ± 225) – (6.595 ± 550) Da were characteristic for non-acclimated larvae. The content of sugars and polyols in supernatants of cold-acclimated and non-acclimated T. molitor larvae was determined. It has been found that glucose concentration in non-acclimated T. molitor larvae was in 1.34 times higher than in cold-acclimated ones. Аcclimated T. molitor larvae had more hydrophilic and less hydrophobic proteins as compared to non-acclimated ones. As well it has been established that non-acclimated T. molitor larvae had low concentrations of polyols (sorbitol and mannite), which were absent in acclimated insects. Probl Cryobiol Cryomed 2016; 26(4): 322–330

Metabolic acclimation of tetraploid and hexaploid wheats by cold stress-induced carbohydrate accumulation

Metabolic acclimation of plants to cold stress may be of great importance for their growth, survival and crop productivity. The accumulation carbohydrates associated with cold tolerance (CT), transcript levels for genes encoding related enzymes along with damage indices were comparatively studied in three genotypes of bread and durum wheats differing in sensitivity. Two (Norstar, bread wheat and Gerdish, durum wheat) were tolerant and the other, SRN (durum wheat), was susceptible to cold stress. During cold stress (−5°C for 24h), the contents of electrolyte leakage index (ELI) in Norstar and then Gerdish plants were lower than that of SRN plants, particularly in cold acclimated (CA) plants (4°C for 14days), confirming lethal temperature 50 (LT50) under field conditions. Increased carbohydrate abundances in the cases of sucrose, glucose, fructose, hexose phosphates, fructan, raffinose, arabinose resulted in different intensities of oxidative stress in bread (Norstar) plants compared to durum plants (SRN and Gerdish) plants as well as in CA plants compared to non-acclimated (NA) ones under cold, indicating metabolic/regulatory capacity along with a decrease in ELI content and enhanced defense activities. A significant decrease in these carbohydrates, particularly sucrose, under cold in NA plants showed an elevated level of cell damage (confirmed by ELI) compared to CA plants. On the other hand, an increase in hexose phosphates, particularly in NA plants, indicated sucrose degradation along with greater production of glucose and fructose compared to CA plants. Under such conditions, a significant increase in transcript levels of sucrose synthase and acidic invertase confirmed these results. Under cold, the high ABA-containing genotypes like Norstar and then Gerdish, which were obvious in CA plants, partly induced relative acclimation of cells for acquisition of CT compared to SRN. These results reveal an important role of carbohydrate metabolism in creating CT in durum wheats (particularly in Gerdish) as well as bread wheat with possible responsive components in metabolic and transcript levels.

Plastic and evolutionary responses to heat stress in a temperate dung fly: negative correlation between basal and induced heat tolerance?

Extreme weather events such as heat waves are becoming more frequent and intense. Populations can cope with elevated heat stress by evolving higher basal heat tolerance (evolutionary response) and/or stronger induced heat tolerance (plastic response). However, there is ongoing debate about whether basal and induced heat tolerance are negatively correlated and whether adaptive potential in heat tolerance is sufficient under ongoing climate warming. To evaluate the evolutionary potential of basal and induced heat tolerance, we performed experimental evolution on a temperate source population of the dung fly Sepsis punctum. Offspring of flies adapted to three thermal selection regimes (Hot, Cold and Reference) were subjected to acute heat stress after having been exposed to either a hot-acclimation or non-acclimation pretreatment. As different traits may respond differently to temperature stress, several physiological and life history traits were assessed. Condition dependence of the response was evaluated by exposing juveniles to different levels of developmental (food restriction/rearing density) stress. Heat knockdown times were highest, whereas acclimation effects were lowest in the Hot selection regime, indicating a negative association between basal and induced heat tolerance. However, survival, adult longevity, fecundity and fertility did not show such a pattern. Acclimation had positive effects in heat-shocked flies, but in the absence of heat stress hot-acclimated flies had reduced life spans relative to non-acclimated ones, thereby revealing a potential cost of acclimation. Moreover, body size positively affected heat tolerance and unstressed individuals were less prone to heat stress than stressed flies, offering support for energetic costs associated with heat tolerance. Overall, our results indicate that heat tolerance of temperate insects can evolve under rising temperatures, but this response could be limited by a negative relationship between basal and induced thermotolerance, and may involve some but not other fitness-related traits.

Effect of protective agents and previous acclimation on ethanol resistance of frozen and freeze-dried Lactobacillus plantarum strains

The aim of this work was to study the protective effect of sucrose, trehalose and glutamate during freezing and freeze-drying of three oenological Lactobacillus plantarum strains previously acclimated in the presence of ethanol. The efficiency of protective agents was assessed by analyses of membrane integrity and bacterial cultivability in a synthetic wine after the preservation processes. No significant differences in the cultivability, with respect to the controls cells, were observed after freezing at −80 °C and −20 °C, and pre-acclimated cells were more resistant to freeze-drying than non-acclimated ones. The results of multiparametric flow cytometry showed a significant level of membrane damage after freeze-drying in two of the three strains. The cultivability was determined after incubation in wine-like medium containing 13 or 14% v/v ethanol at 21 °C for 24 h and the results were interpreted using principal component analysis (PCA). Acclimation was the most important factor for preservation, increasing the bacterial resistance to ethanol after freezing and freeze-drying. Freeze-drying was the most drastic method of preservation, followed by freezing at −20 °C. The increase of ethanol concentration from 6 to 10% v/v in the acclimation medium improved the recovery of two of the three strains. In turn, the increase of ethanol content in the synthetic wine led to a dramatic decrease of viable cells in the three strains investigated. The results of this study indicate that a successful inoculation of dehydrated L. plantarum in wine depends not only on the use of protective agents, but also on the cell acclimation process prior to preservation, and on the ethanol content of wine.

Transcriptome profiling of cold acclimation in bermudagrass (Cynodon dactylon)

Bermudagrass is a warm-season turfgrass that is particularly sensitive to low temperatures. Improvement of cold tolerance may significantly enlarge the total cultivation area of this turfgrass worldwide. The gene expression profiles of four-year-old cold-acclimated bermudagrass versus non-acclimated ones were investigated using Illumina sequencing technology to elucidate the molecular mechanisms underlying cold response in bermudagrass and identify the genes that play important roles in cold response. Results showed that 85,874 and 86,158 unigenes assembled from the reads obtained from cold-acclimated and non-acclimated bermudagrass, respectively. A total of 5867 genes were differentially expressed in cold-acclimated versus non-acclimated bermudagrass, of which 2181 were downregulated (≤ twofold) and 710 were upregulated (≥ twofold) in cold-acclimated compared with non-acclimated bermudagrass. Of the 710 upregulated genes, 34 were highly expressed in cold-acclimated bermudagrass, which was more than nine times higher than in non-acclimated bermudagrass. The AP2, NAC, and WRKY family members of these upregulated genes are associated with cold stress. Transcriptomic sequencing may help determine the mechanism of cold-tolerant bermudagrass, provide a valuable resource for bermudagrass breeding, and offer candidate markers to guide future breeding studies of cold-tolerant bermudagrass.

Study of surface damage on cell envelope assessed by AFM and flow cytometry of Lactobacillus plantarum exposed to ethanol and dehydration.

In this work, we evaluated freeze-drying damage at the surface level of oenological strain Lactobacillus plantarum UNQLp155, as well as its ability to grow in a synthetic wine with and without pre-acclimation. Damage on cell surface was studied by flow cytometry, zeta potential and atomic force microscopy, and cell survival was analysed by plate count. Results showed that beside cells acclimated at lower ethanol concentration (6% v/v) became more susceptible to drying than nonacclimated ones, after rehydration they maintain their increased ability to grow in a synthetic wine. Acclimation at a higher ethanol concentration (10% v/v) produces several damages on the cell surface losing its ability to grow in a synthetic wine. In this work, we showed for the first time that sublethal alterations on bacterial surface induced by a pre-acclimation with a low ethanol concentration (6%), upon a freeze-drying process, result in a better bacterial adaptation to the stress conditions of wine-like medium, as well as to the preservation process. Understanding the adaptation to ethanol of oenological strains and their effects on the preservation process has a strong impact on winemaking process and allows to define the most appropriate conditions to obtain malolactic starters cultures.

Zn2+ -induced changes at the root level account for the increased tolerance of acclimated tobacco plants.

Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress.

Effect of short-term cold stress on oxidative damage and transcript accumulation of defense-related genes in chickpea seedlings

Cold stress affects many plant physiological and biochemical components and induces cascades of alterations in metabolic pathways, amongst them the membrane fatty acid compositions, the activity of antioxidative enzymes and the regulation of gene expression. The present work aimed to characterize the changes of some of these factors in both cold acclimated (CA) and non-acclimated (NA) plants of chickpea (Cicer arietinum L.) to identify the role of the acclimation process in adjusting plant responses to severe cold stress. The results showed an increase in the unsaturated fatty acids (UFAs) ratio compared to saturated fatty acids, which was more obvious in CA plants. Defense enzymes had an important role in CA plants to create greater cold tolerance compared to NA ones in the cases of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX) and lipoxygenase (LOX) activities. During cold stress, a high transcription level of CaCAT and CaSOD genes was detected in CA plants, but a low transcription of CaLOX gene was observed in CA plants compared to NA plants, which might have prevented the decline of UFAs (confirmed by double bond index (DBI) data). Moreover, the transcription level of the Carubisco gene, as an energy producing agent, was higher in CA plants than in NA plants and the transcription of the Catubulin gene, as a crucial substance of cell cytoskeleton, showed a decreasing trend in both CA and NA plants, but this decline was greater in NA plants. These responses showed the possible targets of cold stress as chloroplast and signal transduction to balance stress programs. The above results indicate the crucial role of FA compositions in creating cold tolerance in susceptible chickpea plants with possible responsive components and the possible interactions in protein and transcript levels even in facing extreme cold stress.

The oxidative stress and antioxidant systems in cucumber cells during acclimation to salinity

In the present study, we measured the markers of oxidative stress as well as activity of antioxidative enzymes and content of &alpha;-tocopherol in the acclimated and non-acclimated cucumber (Cucumis sativus L.) cell suspension cultures subjected to 150 and 200 mM NaCl. The content of carbonyl groups and lipid peroxidation were lower in the acclimated cultures than in the non-acclimated ones as well as their increases after NaCl treatments. Both NaCl concentrations enhanced activity of glutathione peroxidase in the examined cultures whereas activity of glutathione-S-transferase rose only in the acclimated ones. The increase in content of &alpha;-tocopherol induced by NaCl was more pronounced in the acclimated cultures. NaCl caused high decline in cell vigour in the non-acclimated cultures up to 80-90 % at the end of the experiment. The presented data suggest that the acclimated cultures coped with the salt stress better than the non-acclimated ones.

Biodegradation of bisphenol-A (BPA) in activated sludge batch reactors: Analysis of the acclimation process

In this work the effect of (a) the sludge age (SA) and the acclimation strategy on the acclimation process of activated sludge (AS) to bisphenol A (BPA), (b) the presence of biogenic substrates on the degradation of BPA, and (c) the acclimation on the degradation of biogenic substrates was studied. AS samples from reactors operated at SA of 30 and 45 d were acclimated to BPA using two strategies: constant or increasing the initial BPA concentration. Although acclimation to BPA was achieved using both strategies, no net biomass growth was detected. Specific BPA degradation rate of acclimated AS ranged between 65 and 90 mgBPA gTSS−1 d−1. BPA degradation was not affected by the biogenic substrates cheese whey or acetate; acclimation to BPA did not cause a negative effect on the biodegradation of these substrates. During the degradation of cheese whey, specific mean oxygen uptake rate (qo2mean) and specific mean substrate consumption rate (qSmean) of non-acclimated AS were similar to those corresponding to acclimated ones. When acetate was tested, qo2mean and qSmean values corresponding to acclimated AS were about twofold the values of the non-acclimated ones. This enhancement could occur because acetate is an intermediate of the metabolism of BPA.

Contrastive responses of spring and winter wheat cultivars to chilling and acclimation treatments

Photosynthesis and antioxidant defense system were investigated under chilling stress without (Ch, 25-4 ºC) and with acclimation (AcCh, 14-4 ºC) in winter (Sabalan) and spring (Zagros) wheat (Triticum aestivum L.) cultivars. Maximum quantum efficiency of photosystem II and CO2 assimilation rate decreased in AcCh ‘Zagros’ but not in ‘Sabalan’, and in contrast, an increase in non-photochemical quenching was observed in ‘Sabalan’ but not in ‘Zagros’. Reduction of leaf starch content was observed in both cultivars while total soluble carbohydrates increased only in ‘Sabalan’ under both Ch and AcCh treatments. Activity of superoxide dismutase was significantly higher in Ch plants and activity of ascorbate peroxidase and catalase was slightly higher in Ch and AcCh plants of both cultivars compared with control. Activity of peroxidase increased in Ch and AcCh plants of ‘Zagros’ while phenylalanine ammoialyase (PAL) activity increased in AcCh ‘Sabalan’. Increase in the leaf content of H2O2 and malondialdehyde (MDA) was more prominent in ‘Zagros’ than in ‘Sabalan’. According to our results, chilling tolerance in winter cultivar was associated with greater thermal dissipation, higher soluble carbohydrates content, greater PAL activity and lower H2O2 and MDA content. Furthermore, acclimated plants were not more protected against chilling injury compared with non-acclimated ones.

Contrastive responses of spring and winter wheat cultivars to chilling and acclimation treatments

Photosynthesis and antioxidant defense system were investigated under chilling stress without (Ch, 25-4 oC) and with acclimation (AcCh, 14-4 oC) in winter (Sabalan) and spring (Zagros) wheat (Triticum aestivum L.) cultivars. Maximum quantum efficiency of photosystem II and CO2 assimilation rate decreased in AcCh ‘Zagros’ but not in ‘Sabalan’, and in contrast, an increase in non-photochemical quenching was observed in ‘Sabalan’ but not in ‘Zagros’. Reduction of leaf starch content was observed in both cultivars while total soluble carbohydrates increased only in ‘Sabalan’ under both Ch and AcCh treatments. Activity of superoxide dismutase was significantly higher in Ch plants and activity of ascorbate peroxidase and catalase was slightly higher in Ch and AcCh plants of both cultivars compared with control. Activity of peroxidase increased in Ch and AcCh plants of ‘Zagros’ while phenylalanine ammoialyase (PAL) activity increased in AcCh ‘Sabalan’. Increase in the leaf content of H2O2 and malondialdehyde (MDA) was more prominent in ‘Zagros’ than in ‘Sabalan’. According to our results, chilling tolerance in winter cultivar was associated with greater thermal dissipation, higher soluble carbohydrates content, greater PAL activity and lower H2O2 and MDA content. Furthermore, acclimated plants were not more protected against chilling injury compared with non-acclimated ones.

Photoprotective mechanisms in cold-acclimated and nonacclimated needles of Picea glehnii

The response of Picea glehnii, a cold-tolerant species in the boreal zone, to air temperature (T) was investigated for its cold-acclimated needles (i.e. the ones subjected to gradual decrease in T) and nonacclimated needles (i.e. the ones subjected to a sudden decrease in T) were compared under low temperature. Cold-acclimated needles showed a greater increase of zeaxanthin and lutein contents than nonacclimated ones, whereas the nonacclimated needles showed a greater increase of thylakoid-bound ascorbate peroxidase (tAPX) activity than cold-acclimated ones under chilling conditions (after cold acclimation). These results suggest that: (1) low T induces the increase of zeaxanthin and lutein content, and tAPX activity; (2) accumulated zeaxanthin and lutein protect needles from photooxidative stress by dissipating excess energy before the reactive oxygen species (ROS) are formed in response to a gradual decrease in T (with cold acclimation and subsequent chilling condition), and by tAPX scavenging ROS formed in the case of a sudden decrease in T (without cold acclimation and chilling condition).

Physiological response to low temperature in the freshwater apple snail, Pomacea canaliculata (Gastropoda: Ampullariidae)

Cold hardiness of the freshwater apple snail, Pomacea canaliculata, varies seasonally. We investigated lethal factors and physiological changes arising from exposure of P. canaliculata to low temperatures. Snails did not survive freezing. The supercooling point of cold-acclimated (cold tolerant) snails (-6.6+/-0.8 degrees C) did not differ significantly from that of non-acclimated ones (-7.1+/-1.5 degrees C) under laboratory conditions. Furthermore, snails died even under more moderately low temperatures approaching 0 degrees C. These results indicate that indirect chilling injury is a factor in the death of P. canaliculata at low temperatures. Regardless of whether the snails were acclimated to low temperatures, all of the dead, and even some of the snails still alive at 0 degrees C, had injured mantles, indicating that the mantle may be the organ most susceptible to the effects of low temperatures. The concentration of glucose in the posterior chamber of the kidney and concentration of glycerol in the digestive gland were significantly higher in cold-acclimated snails than in non-acclimated ones, suggesting carbohydrate metabolic pathways are altered in snails during cold acclimation.