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1.
Storage of ‘Fuji’ apple fruit in a high CO2 (3 kPa) and low O2 (1.5 kPa) controlled atmosphere (CA) reduced firmness and titratable acidity (TA) loss during long term storage. This CA environment also induced development of internal CO2-injury (brown-heart) and slowed the disappearance of watercore. The symptoms of internal CO2-injury were first detected 15 days after CA establishment and the severity increased during the first 4 months of CA-storage. Delaying establishment of CA conditions for 2–12 weeks significantly reduced the severity of CO2-injury. Delaying CO2 accumulation to 3 kPa for 1–4 months during CA (1.5 kPa O2+0.05 kPa CO2) storage also reduced development of CO2-injury symptoms. Delaying CA or CO2 accumulation resulted in lower firmness and TA compared to establishment of CA within 72 h of harvest. However, the delay treatments did result in firmness and TA that were significantly higher compared to values for fruit stored in air. The incidence and severity of senescent injuries (flesh browning and core flush) detected during the late period of storage were greater in air- than CA-stored fruit. The results indicate the susceptibility of ‘Fuji’ apples to CO2-injury is highest during the first weeks of storage after harvest. Delaying establishment of CA or exposure to elevated CO2 after harvest may be a practical strategy to reduce CO2-injury while maintaining other important quality attributes at acceptable levels.  相似文献   

2.
Potato cv. Bintje was grown in open-top-chambers and free-air-CO2-enrichment systems at 7 sites across Europe for 2 years (1998–99). The effect of different treatments (CO2 enrichment and O3 fumigation) on the chlorophyll content of fully expanded upper and lower canopy leaves was investigated collecting Minolta SPAD-502 meter readings. In both CO2 treated and O3 fumigated plants, leaves had lower chlorophyll content than those in ambient air controls; season-long chlorophyll averages were 9.3% lower in the ‘CO2’ treatments, 9.1% lower in ‘O3’ treatments and 12.3% lower in ‘CO2+O3’ treatments. The analysis of chlorophyll content in three different growth phases (Emergence–Tuber Initiation; Tuber Initiation–Maximum Leaf Area; Maximum Leaf Area–Harvest) showed that in the early growth period, i.e. before tuber initiation there was a slight indication for an higher chlorophyll content at elevated CO2 (+3.8%) or O3 (+1.7%). However, from tuber initiation onwards the leaves of plants grown under elevated CO2 or O3 showed a progressively lower chlorophyll content (−4.8% for CO2 treatments and −2.6% for O3 treatments) indicating a faster senescence of leaves that increased during the late growth period (−12.8% for CO2 treatments and −12.7% for O3 treatments) and that was enhanced by CO2–O3 interaction (−17.8%).  相似文献   

3.
The in vitro mortality of eggs and third instar larvae of Anastrepha ludens and A. obliqua was determined after exposure to 21 treatments of air or controlled atmospheres (CA) at high temperatures and 50% RH. Air at 44°C for 160 min caused very low mortality, which increased significantly by CA. Higher temperatures caused a more rapid kill. One hundred percent mortality was achieved for third instar larvae of both species in air or CA at 48°C for 220 min. A 100% mortality of eggs of A. ludens was achieved in air at 51°C for 240 min or in CA at 52°C for 240 min, and 100% mortality of eggs of A. obliqua was achieved in air or in CA at 55°C for 240 min. A. obliqua was slightly more tolerant than A. ludens, and eggs were more tolerant than third instar larvae in both species. CA had a synergistic effect at <50°C, but was slightly less effective than air at higher temperatures. Low O2 concentrations were more effective than high CO2 levels. The mean estimated temperatures for 50, 99 and 99.9968% mortality (LT50s, LT99s, LT99.9968s) of eggs of A. obliqua (the most tolerant) exposed to 0 kPa O2+50 kPa CO2 for 240 min were 49.4, 54.8 and 60.9°C, respectively. We conclude that dry hot air at ≥44°C and 50% RH in CA (0 kPa O2+50 kPa CO2), for 160 min or longer, is effective in increasing mortality of eggs and third instar larvae of A. ludens and A. obliqua.  相似文献   

4.
The effect of delays of 1, 5, 10 or 15 d after harvest in establishing a static controlled atmosphere (SCA) or dynamic controlled atmosphere (DCA) on the quality of ‘Hass’ avocados (Persea americana Mill.) was investigated. Fruit were stored at 5 °C in SCA (5% O2/5% CO2) or DCA (<3% O2/0.5% CO2) for 6 weeks and compared with fruit stored in air. In addition, to determine whether increasing the CO2 in the DCA would affect the fruit quality, DCA-stored fruit were compared with fruit held in a DCA with 5% CO2 (DCA + CO2) established 1 d after harvest. The quality of fruit was assessed at the end of storage and after ripening at 20 °C. DCA-stored fruit ripened in 4.6 d compared with 7.2 d for SCA-stored fruit, or 4.8 d for air-stored fruit. In addition, the incidences of stem end rot (SER), body rot (BR) and vascular browning (VB) were lower in DCA-stored fruit (35%, 29% and 29%, respectively) than in SCA-stored fruit (57%, 52% and 49%, respectively), or air-stored fruit (76%, 88% and 95%, respectively). Delaying the establishment of both SCA and DCA for 15 d resulted in significantly more advanced skin colour at the end of storage (average rating score 11.9) compared with other delay periods (4.6–5.1). There was no significant effect of delay on the time to ripen, skin colour when ripe or any ripe fruit disorder incidence. The incidence of diffuse flesh discolouration (DFD) was not only <1% when averaged over all delays but only occurred at >0.5% incidence in the 15 d delay treatment in DCA (4.8%) and not in SCA. The incidence of diffuse flesh discolouration was 62% in air-stored fruit. Inclusion of 5% CO2 in DCA retarded fruit ripening from 4.7 to 6.9 d and increased the incidence of rots at the end of storage from 5% to 14%, and increased the incidence in ripe fruit of SER from 30% to 56% and of BR from 27% to 55%. It is concluded that fruit quality was better after CA storage than after air storage, and that DCA storage was better than SCA. The effect of DCA is to independently reduce the time to ripen after storage and the incidence of rots when ripe. Delaying the application of SCA or DCA did not affect the expression of rots, but may increase the incidence of DFD. Inclusion of CO2 at 5% in CA retarded fruit ripening but stimulated rot expression and should not be used for CA storage of New Zealand grown ‘Hass’ avocados.  相似文献   

5.
The physiological effects of elevated CO2 and/or O3 on Solanum tuberosum cv. Bintje were examined in Open-Top Chambers during 1998 and 1999 at experimental sites across Europe as part of the EU ‘Changing Climate and Potential Impacts on Potato Yield and Quality’ programme (CHIP). At tuber initiation (≈20 days after emergence, DAE) elevated CO2 (680 μl l−1) induced a 40% increase in the light saturated photosynthetic rate (Asat) of fully expanded leaves in the upper canopy. This was 16% less than expected from short-term exposures of plants grown under ambient CO2 (360 μl l−1) to elevated CO2, indicating that photosynthetic acclimation began at an early stage of crop growth. This effect resulted from a combination of a 12% reduction in stomatal conductance (gs) and a decline in photosynthetic capacity, as indicated by the significant reductions in the maximum carboxylation rate of Rubisco (Vcmax) and light-saturated rate of electron transport (Jmax) under elevated CO2. The seasonal decline in the promotion of photosynthesis by elevated CO2 reflected the concurrent decrease in gs. Vcmax and Jmax were both reduced in plants grown under elevated CO2 until shortly after maximum leaf area (MLA) was attained. Although non-photorespiratory mitochondrial respiration in the light (Rd) increased during the later stages of the season, net photosynthesis was consistently increased by elevated CO2 during the main part of the season. Photosynthetic rate declined more rapidly in response to elevated O3 under ambient CO2, and the detrimental impact of O3 was most obvious after MLA was attained (DAE 40–50). Several exposure indices were compared, with the objective of determining the critical ozone level required to induce physiological effects. The critical O3 exposure above which a 5% reduction in light saturated photosynthetic rate may be expected (expressed in terms of cumulative exposure above 0 nl l−1 O3 between emergence and specific dates during the season (AOT0-cum)) was 11 μl l−1 h; however this value should only be extrapolated beyond the CHIP dataset with caution. The interaction between O3 and stomatal behaviour was more complex, as it was influenced by both long-term and daily exposure levels. Elevated CO2 counteracted the adverse effect of O3 on photosynthesis, perhaps because the observed reduction in stomatal conductance decreased O3 fluxes into the leaves. The results are discussed in the context of nitrogen deficiency, carbohydrate accumulation and yield.  相似文献   

6.
This paper describes the effects of elevated CO2 (550 and 680 μl l−1) and O3 (60 nl l−1 O3 as an 8 h mean), alone or in combination, on canopy development and senescence in potato (Solanum tuberosum L. cv Bintje) across a range of European agro-climatic conditions. The assessments were made within the European CHIP project (CHanging climate and potential Impacts on Potato yield and quality) that was conducted for two growing seasons (1998 and 1999) in free air CO2 enrichment systems (FACE) and open-top chamber facilities (OTCs) at seven European sites. A comparison of chambered and unchambered experimental plots was included to examine the effects of chamber enclosure. Phenological growth stages, plant height, leaf area index (LAI) and the number of green and yellow leaves were recorded non-destructively throughout the growing season and by a destructive intermediate harvest at maximum leaf area (MLA). In the dynamic growth analysis CO2 and O3 effects were studied over three developmental stages: canopy expansion, full canopy and canopy senescence. Chamber enclosures promoted potato crop development (taller plants, more leaves) during the initial growth stages and led to a faster decline of LAI and a higher number of yellow leaves. The growth in ambient plots varied between sites and seasons, as did the scale of the treatment responses. Despite the large background variation, some overall treatment effects could be detected across all sites. Both levels of increased CO2 reduced final plant height in comparison to ambient concentrations, which indicates a premature ending of the active plant growth. At the stage of full canopy and crop senescence the average number of green leaves was significantly (P<0.05) decreased by 680 μl l−1 CO2 (OTC experiments) and LAI showed the same tendency (P=0.07). As there was however no indication of a decreased leaf formation during initial growth and at full canopy, this must have been due to an earlier leaf fall. In the FACE experiments LAI had already began to decline at the stage of full canopy at 550 μl l−1 CO2 but not in ambient CO2 (DAE×CO2, P<0.05). These observations strongly indicated that elevated CO2 induced a premature senescence during full canopy. O3 did not have an overall detrimental effect on crop development during initial growth nor at full canopy, but did induce a faster reduction of LAI during crop senescence (DAE×O3, P<0.05). Final plant height was not affected by O3. There were few CO2×O3 interactions detected. There was a suggestion (P=0.06) that O3 counteracted the CO2-induced decrease of green leaves at full canopy, but on the other hand during crop senescence the decline of LAI due to elevated O3 was faster at ambient compared to elevated CO2 (P<0.05). These responses of canopy development to elevated CO2 and O3 help to explain the treatment responses of potato yield within the CHIP project at sites across Europe.  相似文献   

7.
The aim of this study was to determine the effects of 1-methylcyclopropene, 1-MCP (1 μL L−1 for 24 h at 5 °C) on quality attributes and shelf life of fresh-cut strawberries. The 1-MCP was applied before (whole product) and/or after cutting (wedges), followed by storage in a continuous flow of air or air +1 μL L−1 C2H4. The combined effects of 1-MCP and CaCl2 dips (1% for 2 min) and/or CA (3 kPa O2 + 10 kPa CO2) were also examined. The application of only 1-MCP before and/or after cutting did not have a significant effect on firmness and appearance quality during storage for up to 12 days at 5 °C. The exposure to a continuous flow of 1 μL L−1 C2H4 in air during storage did not increase the softening rate. 1-MCP applied before cutting or both before and after cutting of the strawberries increased respiration rates but reduced C2H4 production rates. Exposure to 1-MCP had a synergistic effect when combined with CaCl2 plus CA. The combined treatment of 1-MCP + CaCl2 + CA slowed down softening, deterioration rates, TA and microbial growth. Compared to the control, which had a 6-day shelf life, the shelf life of fresh-cut strawberries subjected to the combination treatment was extended to 9 days at 5 °C.  相似文献   

8.
A major objective of the ESPACE—wheat programme was to perform by means of open-top chambers (OTCs) ‘standardised’ experimental investigations of spring wheat responses to increased atmospheric CO2 and O3 concentrations and to other environmental stresses at different locations in Europe, representing a broad range of different climatic conditions. From 1994 to 1996 a total number of 25 OTC experiments were carried out. In addition, four growth chamber experiments focusing on key physiological processes of wheat growth in CO2-enriched air were performed. According to the specific needs for subsequent modelling purposes, environmental data were collected during experiments, i.e. air temperature, global radiation, humidity and trace gas concentrations. In the present paper results of these measurements are summarised. It was shown, that the OTC-experiments covered a considerable range of growing season mean-air-temperatures (13.0–23.4°C) and global irradiances (10.8–18.1 MJ m−2 d−1), the most important driving variables for crop growth simulation models. Mean concentrations of CO2 and O3 in ambient air and in different treatments illustrated the observed variability of trace gas exposures between different experiments. Implications for subsequent analyses of biological response data are discussed.  相似文献   

9.
A high temperature/low oxygen pulse improves cold storage disinfestation   总被引：4，自引：0，他引：4  
Short periods of elevated temperature under controlled atmospheres (CA) effectively control insect pests. Cold treatment is also an effective non-chemical disinfestation process. If synergistic effects can be found by combining treatments, these may provide opportunities for cost reduction. Tests were performed to evaluate the tolerance of Packham's Triumph pears (Pyrus communis L.) to a range of temperatures (30–40 °C) combined with low oxygen (O2 < 1 kPa). Treatment duration was 16–48 h and was followed by 1 month storage at 0 °C under air. When held at 30 °C, pears withstood up to 30 h of hypoxia. After cold storage, pears ripened slightly faster than controls but were undamaged. A temperature of 35 °C induced slight skin browning, and 40 °C resulted in substantial skin blackening. Some treatments were also tested on survival of lightbrown apple moth (LBAM), Epiphyas postvittana (Walker). All developmental stages were subjected to either 16 h at 30 °C, or 16 h under hypoxia, or 1 month at 0 °C, or a combination of the three treatments. With all treatments combined, all eggs, larvae and adults were killed. Only 4% of the pupae produced adults and combined treatments led to an increase in pupa mortality of 38%. A combined treatment (tolerated by pears) consisting of 30 h at 30 °C under low O2 plus 1 month cold storage under air, killed 100% of LBAM pupae, and 100% of 5th instar larvae of both codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck). Implementation of such treatments would not require substantial investments for fruit industries equipped with CA storage facilities.  相似文献   

10.
Microbial proliferation and sensory quality aspects of sliced onions were tested at different temperatures (−2, 4 and 10 °C) and atmospheric conditions (with or without 40% CO2 + 59% N2 + 1% O2). The relationships among microorganism growth parameters (the initial cell number (N0), the maximum cell number (Nmax), the maximum specific growth rate (μmax) and lag-phase (λ)) and the microbial or sensory shelf life were determined. The microorganism growth parameters were obtained by fitting the modified Gompertz equation to the microbial counts. The results showed that color intensity (yellowness), sensory scores and microbial counts increased, and firmness decreased during storage. The total plate counts (TPC) provided the best indication of the spoilage organism growth capacity under tested temperatures and atmospheric conditions. The microbial shelf lives of the tested onions in 40% CO2 + 59% N2 + 1% O2, or at −2, 4 and 10 °C, were 12.5, 9.5, 7, 12, 9 and 6 days, respectively, and their sensory shelf lives were 12, 8, 5, 10.5, 7 and 5 days, respectively. The lag time (λ) of the TPC, coliforms, pseudomonads and yeasts correlated well with the microbial and sensory shelf life results. The correlations between microbial and sensory shelf life, and the μmax of TPC, lactic acid bacteria (LAB) and coliforms were between (−0.61 and −0.85). The initial microbial counts (N0) of the five microorganisms showed a slight correlation, and the maximum microbial counts (Nmax) of this group showed no obvious correlation with onion shelf life, apart from the LAB and yeasts.  相似文献   

11.
Spring wheat cv. Minaret crop stands were grown under ambient and elevated CO2 concentrations at seven sites in Germany, Ireland, the UK, Belgium and the Netherlands. Six of the sites used open-top chambers and one used a controlled environment mimicking field conditions. The effect of elevated CO2 for a range of N application regimes, O3 concentrations, and growth temperatures on flag leaf photosynthesis was studied. Before anthesis, flag leaf photosynthesis was stimulated about 50% by 650 compared with 350 μmol mol−1 CO2 at all sites, regardless of other treatments. Furthermore, there was no evidence of a decrease in photosynthetic capacity of flag leaves due to growth at elevated CO2 before anthesis, even for low N treatments. However, photosynthetic capacity, particularly carboxylation capacity, of flag leaves was usually decreased by growth at elevated CO2 after anthesis, especially in low N treatments. Acclimation of photosynthesis to elevated CO2 therefore appears to occur only slowly, consistent with a response to changes in sink–source relationships, rather than a direct response. Effect of elevated CO2 on stomatal conductance was much more variable between sites and treatments, but on average was decreased by ˜10% at 650 compared with 350 μmol mol−1 CO2. Carboxylation capacity of flag leaves was decreased by growth at elevated O3 both before and after anthesis, regardless of CO2 concentration.  相似文献   

12.
'Laiyang Chili’ and ‘Ya Li’ (Pyrus bertschneideri Reld) pears were treated with 3, 6, and 9% emulsions of commercial or refined (reduced -tocopherol levels) plant (soybean, corn, peanut, linseed, and cottonseed) oils at harvest an stored at 0°C for 6 months. Effects of oil treatments on ethylene production, respiration, fruit firmness, fruit color, soluble solid content (SSC), titratable acids (TA), internal browning (IB), and internal CO2, O2, and ethanol were studied. At the same concentration, oil treatments induced similar responses regardless of their sources or their -tocopherol concentrations. In both cultivars, ethylene production and respiration in fruit treated with 9% oils were lower in early storage and higher in late storage than that in the controls. Oils at 6% reduced IB, at 9% inhibited IB completely, and at 3% was not effective after 6 months at 0°C and 7 days at 20°C. Plant oil treatment maintained fruit color, firmness, SSC, and TA in a concentration-dependent manner during storage. In the first 4 months storage, 9% corn oil-treated fruit contained similar partial pressure of CO2 and O2 as the controls. After 5 months storage, oil-treated fruit contained higher partial pressure of CO2 and lower levels of O2 than the controls. When held at 20°C for 7 days, changes of internal CO2 and O2 were slower but partial pressure of CO2 were higher, and O2 were lower, in 9% corn oil-treated fruit than in the controls. Internal ethanol was not affected by oil treatment compared with control, either during storage or 7 days at 20°C. No off-flavor was detected in either oil-treated and control fruit by sensory evaluation.  相似文献   

13.
不同保鲜膜对平菇保鲜效果的影响   总被引：1，自引：0，他引：1  
为比较不同保鲜膜对平菇保鲜效果的影响,分别以低密度聚乙烯(LDPE)膜、高密度聚乙烯(HDPE)膜和聚氯乙烯(PVC)膜为包装材料,在模拟超市冷鲜货架温湿度条件[温度约(14±1)℃,贮藏环境相对湿度约85%]下,研究3种不同保鲜膜对平菇的保鲜效果。结果表明：与LDPE膜相比,HDPE 膜和PVC 膜能降低平菇的采后失重率,维持包装内较高的CO2体积分数和较低的O2体积分数;在贮藏的前4天,HDPE膜和PVC膜包装的平菇感官分值与LDPE膜包装平菇无显著差异(P>0.05);但贮藏4天后,HDPE 膜和PVC膜包装的平菇其感官分值明显低于LDPE膜,且呼吸强度及细胞膜透性也显著高于LDPE膜(P<0.05)。3种不同保鲜膜以LDPE膜对平菇的保鲜效果最佳。  相似文献   

14.
Central to the CHanging climate and potential Impacts on Potato yield and quality project (CHIP) was the consideration of the potential impacts of ozone and CO2 on growth and yield of future European Potato crops. Potato crops, cv. Bintje, were exposed to ambient or elevated ozone; targeted daily average, 60 nl l−1 for 8 h, and ambient or elevated CO2; targeted 680 μl l−1 averaged over the full growing season, in open top chambers (OTCs) at six European sites in 1998 and 1999, or to elevated CO2 (550 μl l−1) in Free Air Carbon dioxide Enrichment facilities (FACE) at two sites in both years. Some OTC experiments included 550 μl l−1. Above and below ground biomass were measured at two destructive harvests; at maximum leaf area (MLA) and at final-harvest. Final-harvest fresh weight yields of marketable-size tubers, >35 mm diameter, from ambient conditions ranged from 1 to 12 kg m−2. There was no consistent (P>0.1) CO2×O3 interaction for growth or yield variables at either harvest. No consistent effects of ozone were detected at the maximum-leaf-area harvest. However, at final harvest, ozone had reduced both above-ground biomass and tuber dry weight (P<0.05), particularly of the largest (>50 mm) size class. These yield losses showed linear relationships both with accumulated ozone exposure; AOT40 expressed as nl l−1 h over 40 nl l−1, and with yields from chambered ambient-ozone treatments (P<0.05) but, because of partial confounding between the treatment AOT40s and the ambient-ozone yields in the data, the two relationships were not completely independent. Yields from ambient-ozone treatments, however, explained a significant (P<0.01) amount of the residual variation in ozone effects unexplained by AOT40. When averaged over all experiments, mean dry weights and tuber numbers from both harvests were increased by elevated CO2. Only green leaf number at the MLA harvest was reduced. The CO2 responses varied between sites and years. For marketable-size tubers, this variation was unrelated to variation in ambient-CO2 treatment yields. Yield increases resulting from the 680 μl l−1 and 550 μl l−1 treatments were similar. Thus elevating [CO2] from 550 to 680 μl l−1 was less effective than elevating [CO2] from ambient to 550 μl l−1. On average, CO2 elevation to 680 μl l−1 increased the dry weight of marketable-size tubers by about 17%, which far exceeded the average ozone-induced yield loss of about 5%. The net effect of raising CO2 and O3 concentrations on the European potato crop would be an increase marketable yield.  相似文献   

15.
Spring wheat cv. Minaret was grown in open-top chambers at four sites across Europe. The effect of different treatments (CO2 enrichment, O3 fumigation, drought stress and temperature) on the chlorophyll content of the flag leaf was investigated using the MINOLTA SPAD-502 meter. Under optimum growth conditions the maximum chlorophyll content, which was reached at anthesis, was consistent among the sites ranging from 460 to 500 mg chlorophyll m−2. No significant effect of elevated CO2 or O3 was observed at anthesis. Leaf senescence, indicated by the chlorophyll breakdown after anthesis, was relatively constant in the control chambers. Under control conditions, thermal time until 50% chlorophyll loss was reached was 600°C day. Elevated CO2 caused a faster decline in chlorophyll content (thermal time until 50% chlorophyll loss was reduced to 500–580°C day) indicating a faster rate of plant development at two experimental sites. The effect of ozone on chlorophyll content depended on the time and dose of O3 exposure. During grain filling, high O3 concentrations induced premature senescence of the flag leaves (up to −130°C day). This deleterious effect was mitigated by elevated CO2. Drought stress led to faster chlorophyll breakdown irrespective of CO2 treatment.  相似文献   

16.
Modified atmosphere packaging alleviates chilling injury in cucumbers   总被引：7，自引：0，他引：7  
Cucumbers (Cucumis sativus L.) packaged in perforated or sealed 31.75 μm (1.25 mil) low density polyethylene (LDPE) bags were found to have less severe chilling injury than nonwrapped fruit in storage at 5 °C and 90–95% relative humidity. The onset of chilling injury was also delayed by the LDPE packaging compared to the nonpackaged control. The concentrations of CO2 increased to 3% while O2 levels decreased to 16% in the sealed bags. Fruit in the sealed bags had the least decay. The O2 and CO2 concentrations inside the perforated bags changed very little from the ambient atmosphere. However, there was a marked difference in the weight loss between nonwrapped cucumbers and fruit from perforated or sealed bags. The weight loss of nonwrapped fruit reached 9% in 18 days while perforated and sealed samples lost less than 1% during the same period. Chilling stress induced increases in putrescine levels in all treatments but the sealed fruit had the highest levels of putrescine. Sealed fruit and perforated fruit also had higher content of spermidine than non-wrapped fruit. These high levels of polyamines may have contributed to the increase of chilling tolerance in fruit from perforated and sealed packages.  相似文献   

17.
One of the major goals of the European Stress Physiology and Climate Experiment (ESPACE-wheat) was to investigate the sensitivity of wheat growth and productivity to the combined effects of changes in CO2 concentration, ozone and other physiological stresses. Experiments were performed at different sites throughout Europe, over three consecutive growing-seasons using open-top chambers. This paper summarizes the main experimental findings of the effects of CO2 enrichment and other factors i.e. ozone (O3), drought stress or nitrogen supply on the biomass and yield of spring wheat (Triticum aestivum cv. Minaret). Final harvest data from different sites and seasons were statistically analysed: (1) to identify main effects and interactions between experimentally controlled factors; and (2) to evaluate quantitative relationships between environmental variables and biological responses. Generally, ‘Minaret’ wheat did not respond significantly to O3, suggesting that this cultivar is relatively tolerant to the O3 levels applied. The main effect of CO2 was a significant enhancement of grain yield and above-ground biomass in almost all experiments. Significant interactions between CO2 and other factors were not common, although modifications in different N- and water supplies also led to significant effects on grain yield and biomass. In addition, climatic factors (in particular: mean air temperature and global radiation) were identified as important co-variables affecting grain yield or biomass, repectively. On average, the yield increase as a result of a doubling of [CO2] was 35% compared with that observed at ambient CO2 concentrations. However, linear regressions of grain yield or above-ground biomass for individual experiments revealed a large variability in the quantitative responses of ‘Minaret’ wheat to CO2 enrichment (yield increase ranging from 11 to 121%). Hence, CO2 responsiveness was shown to differ considerably when the same cultivar of wheat was grown at different European locations. Multiple regression analyses perfomed to evaluate the relative importance of the measured environmental parameters on grain yield indicated that although yield was significantly related to five independent variables (24 h mean CO2 concentration, 12 h mean O3 concentration, temperature, radiation, and drought stress), a large proportion of the observed variability remained unexplained.  相似文献   

18.
以酥梨为试材,研究了(0±0.5)℃条件下不同O2浓度梯度和CO2浓度梯度的气调贮藏对酥梨采后生理及果实褐变的影响。结果表明:在贮藏期内,当CO2浓度为0%时,随着O2浓度的降低,在一定程度上可以延缓酥梨果肉组织相对电导率的升高、酚类物质的下降、多酚氧化酶活性的上升及色泽的转黄;但当O2浓度为1.5%时,会对酥梨果实造成伤害,引起多酚氧化酶活性上升,果心褐变指数升高;当O2浓度为5%时,CO2浓度的升高有效保持了果实的硬度、色泽;但当CO2浓度为8%时,会导致酥梨果实相对电导率增幅加大,果心、果肉酚类物质氧化加剧,果心褐变指数升高。综上所述,酥梨适宜的气调指标阈值为CO2<2%,O2为3%~5%。  相似文献   

19.
In rape (Brassica napus L., cv. Global) seed growth mainly depends on husk CO2 assimilation. In irrigated plants, the net photosynthetic rate (Amax) was 10–13 μmol CO2 m−2 s−1 in non-maturing pods and correlated with nitrogen content. The stomatal conductance of water vapour (gH2O) was 0.3 mol m−2 s−1 in non-maturing pods. The photosynthetic nitrogen use efficiency (NUE) was 8.3 μmol CO2g−1 N s−1, about one-third of that in leaves. The photosynthetic water use efficiency (WUE; AmaxgH2O−1) was similar in pods and leaves. In severely droughted plants, the photosynthetic rate was reduced to 38%. The seed growth rate, however, was not influenced by intermittent periods of water stress, indicating translocation of assimilates to the seeds. The drought resistant character of the pods was due to low specific area, succulence, low stomatal conductance causing a small decrease of ΔΨ day−1 during soil drying and maintenance of high relative water content during severe drought. A mathematical formulation of the pod water release curve was undertaken. © (1997) Elsevier Science B.V.  相似文献   

20.
Use of a biodegradable laminate of a chitosan-cellulose and polycaprolactone as a film for modified atmosphere packaging (MAP) of fresh produce was tested. The temperature dependence of O2, CO2 and N2 gas permeability coefficients for the biodegradable laminate was examined. The coefficients increased linearly with increasing temperature in the range 10–25 °C. The coefficients were validated by experiments on MAP with shredded lettuce and shredded cabbage. MAP systems with head lettuce, cut broccoli, whole broccoli, tomatoes, sweet corn and blueberries were designed using the gas permeability coefficients. The gas composition in each biodegradable package including the fresh produce was simulated to be close to the optimal composition. The biodegradable laminate was found suitable as a packaging material for storage of fresh produce.  相似文献   

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