Effects of elevated CO2 and/or ozone on nutrient concentrations and nutrient uptake of potatoes

Potato crops were grown at seven sites across Europe to test the effects of elevated atmospheric carbon dioxide and/or tropospheric ozone concentrations on growth, yield and various aspects of potato tuber quality within the framework of the EC funded programme Changing Climate and Potential Impacts on Potato Yield and Quality (CHIP). Field exposure systems were used to enrich the atmosphere in CO₂ and/or ozone. At five of the sites, nutrient element conconcentrations (macronutrients: nitrogen, phosphorus, potassium, calcium, magnesium, and micronutrients: mangenese, zinc, iron) in different parts of plants from the various treatments were analysed. Under elevated CO₂, nearly all nutrient elements tended to decrease in concentration. At maximum leaf area, a significant reduction was observed for the concentrations of nitrogen and potassium both in aboveground biomass and in tubers, and for calcium in tubers. Since CO₂ enrichment promoted early tuber growth, these effects could in part be attributed to tuber developmental stage. At maturity, potato grown under CO₂ enrichment exhibited significantly lower concentrations of nitrogen, manganese and iron in aboveground organs, and of nitrogen, potassium and magnesium in tubers which means a reduction of tuber quality. In contrast to CO₂, elevated ozone tended to increase tuber nutrient element concentrations. This was significant for nitrogen and manganese. CO₂ effects on tuber biomass increase were more pronounced than CO₂ effects on nutrient element decrease. Thus, the total amount of nutrient elements taken up by potato crops increased under elevated CO₂. Fertiliser practice in a future, CO₂-rich world will have to be adjusted accordingly.     

Photosynthetic and stomatal responses of potatoes grown under elevated CO2 and/or O3—results from the European CHIP-programme

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 (A_sat) 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 (g_s) and a decline in photosynthetic capacity, as indicated by the significant reductions in the maximum carboxylation rate of Rubisco (Vc_max) and light-saturated rate of electron transport (J_max) under elevated CO₂. The seasonal decline in the promotion of photosynthesis by elevated CO₂ reflected the concurrent decrease in g_s. Vc_max and J_max 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 (R_d) 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.     

Effects of elevated carbon dioxide and ozone on potato tuber quality in the European multiple-site experiment ‘CHIP-project’

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.     

Climatic conditions and concentrations of carbon dioxide and air pollutants during ‘ESPACE—wheat’ experiments

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.     

Chlorophyll content of spring wheat flag leaves grown under elevated CO2 concentrations and other environmental stresses within the ‘ESPACE-wheat’ project

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.     

Growth and yield responses of spring wheat to increasing carbon dioxide, ozone and physiological stresses: a statistical analysis of ‘ESPACE-wheat’ results

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.     

Phenological development, leaf emergence, tillering and leaf area index, and duration of spring wheat across Europe in response to CO2 and ozone

Phenological development, leaf emergence, tillering and leaf area index (LAI), and duration (LAD) of spring wheat cv. Minaret, grown in open-top chambers at different sites throughout Europe for up to 3 years at each site, were investigated in response to elevated CO₂ (ambient CO₂×2) and ozone (ambient ozone ×1.5) concentrations.

Phenological development varied among experiments and was partly explained by differences in temperature among sites and years. There was a weak positive relationship between the thermal rate of development and the mean daylength for the period from emergence to anthesis. Main stems produced on average 7.7 leaves with little variation among experiments. Variation was higher for the thermal rate of leaf emergence, which was partly explained by differences in the rate of change of daylength at plant emergence among seasons. Phenological development, rate of leaf emergence and final leaf number were not affected by CO₂ and ozone exposure. Responses of tillering and LAI to CO₂ and ozone exposure were significant only in some experiments. However, the direction of responses was consistent for most experiments. The number of tillers and ears per plant, respectively, was increased as a result of CO₂ enrichment by about 13% at the beginning of stem elongation (DC31), at anthesis and at maturity. Exposure to ozone had no effect on tillering. LAI was increased as a result of CO₂ elevation by about 11% at DC31 and by about 14% at anthesis. Ozone exposure reduced LAI at anthesis by about 9%. No such effect was observed at DC31. There were very few interactive effects of CO₂ and ozone on tillering and LAI. Variations in tillering and LAI, and their responses to CO₂ and ozone exposure, were partly explained by single linear relationships considering differences in plant density, tiller density and the duration of developmental phases among experiments. Consideration of temperature and incident photosynthetically active radiation in this analysis did not reduce the unexplained variation. There was a negative effect of ozone exposure on leaf area duration at most sites. Direct effects of elevated CO₂ concentration on leaf senescence, both positive and negative, were observed in some experiments. There was evidence in several experiments that elevated CO₂ concentration ameliorated the negative effect of ozone on leaf area duration. It was concluded from these results that an analysis of the interactive effects of climate, CO₂ and ozone on canopy development requires reference to the physiological processes involved.     

Leaf and green area development of durum wheat genotypes grown under Mediterranean conditions

Future increases in the potential yield of wheat will require an improvement in the photosynthetic area in early growth stages. Our aim was to investigate the genotypic and environmental effects on the pattern of leaf and green area development of durum wheat (Triticum turgidum L. cv. durum). Twenty-five genotypes were grown during 2 years under irrigated and rainfed conditions in Lleida (northeastern Spain). Leaf area index (LAI) and green area index (GAI) were determined on eight occasions from seedling to maturity and data were fitted to an asymmetric logistic peak curve. Multivariate analysis of variance was used to assess the curve characteristics responsible for differences between years, sites and genotypes. Genotypic differences in the pattern of changes in LAI and GAI from sowing to maturity were not statistically significant, indicating a lack of genetic diversity for these traits in the germplasm used in this study. A decrease in the peak of the curves of 27% for LAI and 35% for GAI was observed under rainfed conditions compared to the irrigated site. Drought caused a lengthening of crop development until anthesis of about 2% (3–4 days). Contrarily, the time from sowing to the maximum LAI and GAI values were reduced by drought in around 10%, causing an acceleration of the onset of plant senescence. Once started, the senescence of the green organs of the plant was more rapid at the irrigated than at the rainfed site. It is concluded that LAI and GAI patterns were more influenced by the environment (mainly water availability) than by the genotype. The results suggest a certain degree of independent regulation for phenological development and the swiftness of green area accumulation in the plant.     

Effects on nutrients and on grain quality in spring wheat crops grown under elevated CO2 concentrations and stress conditions in the European, multiple-site experiment ‘ESPACE-wheat’

Nutrient element concentrations and grain quality were assessed in spring wheat grown under elevated CO₂ concentrations and contrasting levels of tropospheric ozone at different nitrogen supply rates at several European sites. Carbon dioxide enrichment proved to affect nutrient concentrations in a complex manner. In green leaves, all elements (with exception of phosphorus and iron) decreased. In contrast, effects on the element composition of grains were restricted to reductions in nitrogen, calcium, sulphur and iron. Ozone exposure resulted in no significant effects on nutrient element concentrations in different tissues in the overall analysis. The nitrogen demand of green tissues was reduced due to CO₂ enrichment as shown by reductions in the critical leaf nitrogen concentration and also enhanced nitrogen use efficiency. Reductions in the content of ribulose-bisphosphate carboxylase/oxygenase and repression of the photorespiratory pathway and reduced nitrogen allocation to enzymes driving the photosynthetic carbon oxidation cycle were chiefly responsible for this effect. Thus, nitrogen acquisition by the crop did not match carbon acquisition under CO₂ enrichment. Since crop nitrogen uptake from the soil was already completed at anthesis, nitrogen allocated to the grain after anthesis originated from vegetative pools—causing grain nitrogen concentrations to decrease under CO₂ enrichment (on average by 15% when CO₂ concentrations increased from 360 to 680 μmol mol⁻¹). Correspondingly, grain quality was reduced by CO₂ enrichment. The Zeleny value, Hagberg value and dry/wet gluten content decreased significantly with increasing [CO₂]. Despite the beneficial impact of CO₂ enrichment on growth and yield of C₃ cereal crops, declines in flour quality due to reduced nitrogen content are likely in a future, [CO₂]-rich world.     

Effects of elevated CO2 and cutting frequency on the productivity and herbage quality of a semi-natural grassland

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.     

Interactive effects of elevated atmospheric CO2 concentrations and plant available soil water content on canopy evapotranspiration and conductance of spring wheat

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 (E_C) 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. E_C 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 (G_C) calculated as E_C 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 G_C versus APAR as well as G_C 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 (T_PAW, ca. 40 mm) could be identified above which G_C did not respond to PAW. While in 1998 G_C did not respond to elevated [CO₂] at PAW < T_PAW, it was slightly increased at low PAW values in the field experiments of 1999. The reduction of T_PAW 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.     

NaCl和Na2 CO3+NaHCO3对玉米种子萌发及幼苗生长的影响差异研究

将NaCl和Na2CO3+NaHCO3两种盐分别设置4个浓度梯度,以玉米发芽率、分布频率、幼苗期的苗高、主胚根长及相对盐害率为指标,研究两类盐对玉米萌发和苗期胁迫的生理差异.结果表明,两种盐胁迫处理的发芽率、苗高、主胚根长的平均值均随浓度增加而降低,Na2CO3+NaHCO3处理比NaCl处理胁迫盐害率严重.各品种耐NaCl和Na2CO3+NaHCO3能力并不一致.     

The effects of climatic variation in Europe on the yield response of spring wheat cv. Minaret to elevated CO2 and O3: an analysis of open-top chamber experiments by means of two crop growth simulation models

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.     

大豆叶片响应CO2浓度升高、干旱及其交互作用的转录组分析

气候变暖及大气CO₂浓度升高成为全球共识,由此增加极端天气气候事件(干旱)发生的频率和强度并对大豆生产带来不确定性。本研究通过大豆表型和叶片转录组测序(RNA-seq)分析,阐释CO₂浓度升高、干旱及其交互条件对大豆基因表达影响,明确CO₂浓度升高影响大豆耐旱性的调控途径,并在两个不同遗传背景品种中验证,从分子水平为未来气候变化背景下大豆抗旱育种提供理论参考。表型结果表明, CO₂浓度升高促进了大豆的生长并缓解干旱胁迫的负面效应。叶片转录组测序分析共筛选到89个CO₂响应基因, KEGG分类显示这些基因主要参与抗氧化物质(萜类、黄酮类等)代谢,同时特异性差异表达基因功能主要集中在细胞组分和生长发育方面。干旱条件下筛选的1006个差异表达(16倍)基因主要参与各类氨基酸(脯氨酸、色氨酸等)代谢途径,绝大多数蛋白质合成与转运相关基因上调,表明干旱胁迫下大豆叶片内物质合成交换过程加强。交互条件下筛选出的8566个差异表达基因主要参与碳水化合物代谢,光合作用-天线蛋白途径的相关基因几乎...     

Pb胁迫下氮素形态对日本毛连菜生物量、叶绿素含量及抗氧化酶活性的影响

为揭示Pb胁迫下氮素形态及施氮量对日本毛连菜生长及生理生化特性的影响,采用盆栽试验方法,针对不同浓度Pb胁迫下铵态氮和硝态氮及其施氮量对日本毛连菜生物量、叶绿素含量和抗氧化酶活性的影响进行研究。结果表明,在Pb胁迫下,日本毛连菜的生物量随施氮量的增加总体呈先上升后下降的趋势。在低浓度Pb胁迫下,施用铵态氮肥时,日本毛连菜叶绿素含量和CAT活性随施氮量的增加呈先升后降的趋势,SOD活性逐渐增加,POD活性呈先降后升的趋势,施用硝态氮肥时,植株叶绿素含量和SOD活性的变化趋势为先升后降,POD和CAT的活性呈逐渐下降的趋势;在高浓度Pb胁迫下,施用铵态氮肥时,日本毛连菜叶绿素含量、POD活性随施氮量的增加呈先升高后降低的趋势,而SOD、CAT活性则呈先降低后升高的趋势,施用硝态氮肥时,CAT活性随施氮量的增加呈先上升后下降的趋势,其他指标则无明显的变化趋势。无论在何种Pb浓度胁迫下,适量的铵态氮肥更有利于日本毛连菜的生长,不仅能提高叶片叶绿素含量,还能增加其抗氧化酶活性,这对于增加日本毛连菜的生物量,提高其修复铅污染土壤的能力具有实际意义。     

Apical Development and Growth of Barley under Different CO2 and Nitrogen Regimes

Increases in atmospheric carbon dioxide (CO₂) concentration have stimulated interest in the response of agricultural crops to elevated levels of CO₂. Several studies have addressed the response of C₃ cereals to CO₂, but the interactive effect of nutrient supply and CO₂ on apical development and spikelet set and survival has not been investigated thoroughly. Hence, an experiment was conducted in the greenhouse to evaluate the effect of high (700 μmol CO₂mol^?1 air) and low (400 μmol mol^?1) levels of atmospheric CO₂ on apical development, spikelet set and abortion, and pre- and post-anthesis growth in spring barley (Hordeum vulgare L.) grown under high N (0.3 g N pot^?1 before sowing ?1–0.11 g N pot^?1 week^?1) and low N (0.3 g N pot^?1) regimes. The plants were grown in 5 L pots. Development of spike was hastened due to CO₂ enrichment, and the C+ plants pollinated few days earlier than the C— plants. Carbon dioxide enrichment had no effect on date of ripening. Development of spike slowed following application of extra N, and plants pollinated 10 days later and matured 2 weeks later when compared with plants under low N. Carbon dioxide enrichment did not affect the number of spikelets at anthesis. Excess N decreased spikelet abortion and the increased maximum number of spikelets under both [CO₂]. Barley plants did not tiller when grown in low [CO₂] and low N. Increased endogenous IAA concentration in those plants, recorded three days before tillers appeared in other treatments, may have contributed to this. Carbon dioxide enrichment increased the C concentration of plants, but decreased the N concentration under high N regime. Both the C and N concentration of plants were increased under high N regime. Carbon dioxide enrichment increased the total dry matter of mature plants by 9 % under high N regime and by 21 % under low N regime. Under high [CO₂] increased kernel number on tiller spikes, and increased kernel weight both on main stem and on tiller spikes resulted in a 23 % increase in kernel yield under low N regime and 76 % increase in kernel yield under high N regime. The rate of N application influenced growth and yield components to a greater extent than CO₂ enrichment. At maturity, plant dry matter, kernel weight, the number of kernels per spike, and the number of spikes per plant were higher under high N regime than under low N regime. Long days (16 h), low light intensity (280 μmol m^?2s^?1), and at constant temperature of 20 °C high [CO₂] increased kernel weight and the number of kernels on tiller spikes under high and low N application rate, but did not increase the number of kernels on main stem spike, or the number of tillers or tiller spikes per plant.     

转TERF1和LeERF2双价基因旱稻及其逆境光合特性研究

为了提高旱稻干旱、盐及低温综合胁迫的抗性，构建了含有抗旱抗盐功能的TERF1和抗盐抗冷功能的LeERF2转录因子的双价植株表达载体；以秦爱、旱65和旱297三种旱稻品种为材料, 通过农杆菌介导法将以上两转录因子转入受体材料中，获得了经PCR及Southern检测证实同时整合双价基因的T₀及T_{1相似文献}