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1.
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   

2.
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   

3.
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   

4.
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   

5.
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   

6.
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   

7.
'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   

8.
The main objective of the CHIP project was to perform ‘standardised’ investigations of potato (Solanum tuberosum L. cv Bintje) responses to increased O3 and CO2 concentrations by means of open-top chambers (OTC) and free air carbon dioxide enrichment (FACE) systems. The experimental sites are located across Europe representing a broad range of different climatic conditions. In 1998 and 1999 a total number of 12 OTC experiments and four FACE experiments were conducted. According to the specific needs for subsequent modelling purposes, environmental data were collected during experiments, i.e. air temperature, global radiation, air humidity (vapour pressure deficit (VPD)), soil moisture and trace gas concentrations. In the present paper, the results of these measurements are summarised. It was shown that the experiments covered a considerable range of growing season mean air temperatures (13.8–19.9 °C) and global irradiances (12.0–21.3 MJ m−2 per day), the most important driving variables for crop growth simulation models. Analysis of the soils used during the experiments demonstrated that in most cases sufficient nutrient elements were available to guarantee an undisturbed growth. Mean concentrations of CO2 and O3 in ambient air and in different treatments illustrate the observed variability of trace gas exposures between different sites and experiments. However, the effects of these parameters on growth and yield are subject of separate papers. The general climatic conditions across Europe are also causing important growth and yield effects. Comparison of marketable tuber yields revealed an increase at higher latitudes. This result was associated with lower temperatures and VPD and longer day lengths at the higher latitudes, which in turn were associated with longer growing seasons.  相似文献   

9.
Potato (Solanum tuberosum L cv. Bintje) was exposed to ambient and elevated carbon dioxide (CO2), to ambient and elevated ozone (O3) and to elevated levels of both gases during two growing seasons, 1998 and 1999. Experiments in open-top chambers (OTC) were carried out in Finland, Sweden, Ireland, United Kingdom, Germany and Belgium and a FACE (Free Air Carbon dioxide Enrichment) experiment was carried out in Italy. In OTCs the plants were grown under ambient CO2 concentrations or with 550 and 680 μl l−1 CO2 alone or in combination with ambient or elevated O3 concentrations (target seasonal mean of 60 nl l−1 8 h per day). In the FACE systems the plants were exposed to ambient or 550 μl l−1 CO2. In the OTC experiments the reducing sugar content of potato tubers decreased significantly with increased concentration of O3. The starch content of potato tubers decreased, with negative impact on tuber quality, but the ascorbic acid concentration increased as a function of the AOT40 (The sum of the differences between hourly ozone concentration and 40 nl l−1 for each hour when the concentration exceeds 40 nl l−1 during a relevant growing season). However, simultaneous exposure to elevated CO2 counteracted the ozone effect. With increase in the CO2 exposure, glycoalkaloid and nitrate concentrations decreased yielding improved quality, while the citric acid concentration decreased causing a higher risk for discoloration after cooking. The amount of dry matter and starch increased significantly in the FACE experiment.  相似文献   

10.
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   

11.
In the ESPACE-Wheat programme, 25 open-top chamber experiments were carried out in 1994, 1995 and 1996, on nine locations, divided over eight European countries. In most experiments, spring wheat cv. Minaret was subjected to two levels of atmospheric CO2 and two levels of ozone. Grain yields in the control treatments (ambient levels of CO2 and O3) varied strongly between sites. Also, yield response to elevated CO2 and O3 showed great variation. The present study was conducted to determine whether climatic differences between sites could account for the observed variation.

Two simulation models were used for the analysis: AFRCWHEAT2-O3 and LINTULCC. AFRCWHEAT2-O3 simulates phenology, canopy development and photosynthesis in greater detail than LINTULCC. Both models account for the effects of radiation and temperature on crop growth. New algorithms were developed to simulate the effects of CO2 and O3. Weather data that were measured in the experiments were used as input, and simulated growth responses to CO2 and O3 were compared with measurements. No attempt was made to merge the two models. Thus two independent tools for analysis of data related to climate change were developed and applied.

The average measured grain yield in the control treatment, across all 25 experiments, was 5.9 tons per hectare (t ha−1), with a standard deviation (SD) of 1.9 t  ha−1. The models predicted similar average yields (5.5 and 5.8 t ha−1 for AFRCWHEAT2-O3 and LINTULCC, respectively), but smaller variation (SD for both models: 1.2 t ha−1). Average measured yield increase due to CO2-doubling was 30% (SD 22%). AFRCWHEAT2-O3 expected a slightly lower value (24%, SD 9%), whereas LINTULCC overestimated the response (42%, SD 11%). The average measured yield decrease due to nearly-doubled O3 levels was 9% (SD 11%). Both models showed similar results, albeit at lower variation (7% yield decrease at SDs of 6 and 4%). Simulations accounted well for the observation that, at elevated CO2, the percentage yield loss due to O3 was lower than at ambient CO2.

The models predicted lower variation among sites and years than was measured. Yield response to CO2 and O3 was predicted to depend on the climate, with a predominant effect of temperature on the response to CO2. In the measurements, these climatic effects were indeed observed, but a greater part of the variation was not related to light intensity, temperature, CO2, or O3. This unexplained variability in the measured dataset was probably caused by factors not accounted for in the models, possibly related to soil characteristics.

We therefore conclude that even perfect information on the climate variables examined in ESPACE-Wheat, i.e. light intensity and temperature, by itself would be insufficient for accurate prediction of the response of spring wheat to future elevated levels of CO2 and O3.  相似文献   


12.
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   

13.
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   

14.
The response of cabbage to controlled atmospheres (CA) of 1–3% O2 and 1–10% CO2; 3% O2 and 5% CO2 was studied in relation to the incidence of physiological and pathological disorders. Fungal infections, pepper spot, low oxygen injury, weight loss, colour, odour, flavour and ethanol were evaluated. The findings show that CA did not reduce Botrytis cinerea rot in comparison to low temperature storage in air. PVC film and CA, on the other hand, reduced pepper spot by over 50% with respect to the air control. In particular, pepper spot was eliminated by high CO2 (10%) levels. Low O2 (1% O2 and 1% CO2) atmospheres caused 33 and 50% injury respectively after 89 and 109 days of storage. CA and PVC film reduced weight loss to 1%, as compared with 11% in the heads in air, which had shrivelled. The combination of 3% O2/5% CO2 and PVC film delayed yellowing with respect to air control. Concentrations of 1–3% O2 and 10% CO2 resulted in off odours and flavours after 74 days of storage. This result was confirmed by a considerable increase in ethanol concentrations. The most effective concentration tested was 3%O2/5%CO2 although, in general, infection by B. cinerea limited the storage life.  相似文献   

15.
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   

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.
Monoliths of a fertile, although N limited, C3 grassland community were subjected (or not) to an atmospheric CO2 enrichment (600 μmol mol−1), owing to the Mini-FACE system from August 1998 to June 2001, at two contrasting cutting frequencies (3 and 6 cuts per year). The present study reports the effects of elevated CO2 on the above-ground productivity and on the herbage quality. Elevated CO2 did not affect the dry matter (DM) yield of the swards in 1999. In 2000, the second year, there was a positive CO2 effect (+26%) both on the DM and on the nitrogen yields (+30%). With the frequently cut monoliths, the DM of the legume component of the sward was strongly increased by elevated CO2. This effect became also significant in July 2000 for the low cutting frequency treatment. These results are in good agreement with the concept of an increased legume development and symbiotic N2 fixation triggered by an increased ecosystem scale demand of N under elevated CO2. At a low cutting frequency, the DM of the forbs was strongly increased in elevated compared with ambient CO2. This increased development of the forbs apparently led to a competitive decline of the grasses. Therefore, the total DM yield response to CO2 was smaller at a low (+15%) compared with a high (+36%) cutting frequency in 2000. An increase in the water soluble sugar content of the bulk forage under elevated CO2 and a corresponding decline in cell wall contents (NDF) were observed. In June 1999, the decline in NDF was correlated with an increased in-vitro DM digestibility. The forage quality was also indirectly affected by elevated CO2 through changes in leaf:stem ratio and in botanical composition. At a low cutting frequency, the increased forb content favoured the herbage quality because of a higher digestibility of the forb shoots and, indirectly, through the reduction in the mass of the grass stems. These results emphasise the role of species dynamics for elevated CO2 impacts on semi-natural grassland productivity and herbage quality.  相似文献   

18.
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   

19.
The present study was conducted to investigate the possible interactive effects of rising atmospheric CO2 concentration [CO2] and drought stress on water use of wheat. Spring wheat (Triticum aestivum cv. “Minaret”) was grown either in 1 m diameter lysimeters with 0.4 m soil depth (1998) or in the field (1999) in open-top chambers under two CO2-concentrations (ambient, ambient + 280 ppm) and two watering regimes (well-watered = WW with a plant available water content PAW > 40 mm and drought stressed = DS, 10 mm < PAW < 30 mm) beginning after first node stage. Canopy evapotranspiration (EC) was measured continuously from first the node stage until the beginning of flag leaf senescence using four open-system canopy chambers (0.78 m3). Seasonal changes of the absorption of photosynthetically active radiation (APAR) of the canopy and root growth (1999) were also measured.

In both growing seasons leaf area index increased in response to elevated [CO2] in both water treatments. The related effects of [CO2] on canopy radiation absorption (APAR) were, however, smaller. EC was linearily related to APAR in both growing seasons. While elevated [CO2] reduced the slope of this relation under WW conditions by ca. 20% in both growing seasons, it was not reduced (1998) and even increased (1999) under drought. Canopy conductance (GC) calculated as EC divided by vapour pressure deficit of air, showed a non-linear relationship to APAR that was best explained by saturation curves. Under WW conditions, elevated [CO2] reduced the initial slope of GC versus APAR as well as GC at saturating light conditions (ca. −30%), while under DS conditions no effect of elevated [CO2] could be detected. Under high light conditions (PAR > 400 μmol m−2 s−1) a critical “threshold value” of PAW (TPAW, ca. 40 mm) could be identified above which GC did not respond to PAW. While in 1998 GC did not respond to elevated [CO2] at PAW < TPAW, it was slightly increased at low PAW values in the field experiments of 1999. The reduction of TPAW by elevated [CO2] may be explained by enhanced root growth (1999) that would have given the plants better access to soil water resources. The present results suggest that below a critical soil water content elevated [CO2] will not reduce canopy water loss of wheat or may even enhance it.  相似文献   


20.
为阐明大气CO2浓度升高和不同氮素水平对湿地植物光合生理特性和生长的影响,本研究以三江平原湿地优势植物小叶章(Calamagrostis angustifolia)为研究对象,通过野外原位控制试验,利用开顶式气室(OTC)模拟环境大气CO2浓度变化,设置E0(380 ±20 µmol/mol)、E1(550 ±20 μmol/mol)和E2(700 ± 20 μmol/mol)3个CO2浓度;在每个OTC内设置 N0(0 g N/m2)、N1(4 g N/m2)和N2(8 g N/m2)3个氮素水平。结果表明,N0条件下,与E0处理相比,E1和E2处理（72 天）后小叶章叶片净光合速率分别降低11%和12%(P<0.05),其叶片可溶性蛋白含量、氮素含量（CO2熏蒸72 天）、小叶章株高（CO2熏蒸86 天）均显著低于E0处理(P<0.05);N1条件下,与E0处理相比,E1和E2处理（72 天）后小叶章叶片净光合速率降低5%(P>0.05)和10%(P<0.05),其叶片氮素含量(P<0.05)、小叶章株高均低于E0处理;N2条件下,E1和E2处理（72 天）小叶章净光合速率均呈稍增加的趋势(P>0.05),其叶片可溶性蛋白含量显著增加(P<0.05),氮素含量和小叶章株高无显著变化(P>0.05)。N0、N1和N2条件下,CO2浓度升高均显著增加了小叶章叶片可溶性糖含量。本研究表明长期CO2浓度升高可能通过降低小叶章叶片光合酶活性,进而降低了其净光合速率,而施加高浓度的氮肥可以缓解长期高CO2浓度对湿地植物光合及生长的负面影响。  相似文献   

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