CO2和O3浓度倍增及其复合作用对大豆叶绿素含量的影响

利用开顶箱(OTC)法研究了在CO2和O3浓度倍增及其复合作用下,大豆叶片叶绿素含量及叶绿素a／b值的变化规律。结果表明,不同生育时期大豆叶片中叶绿素含量不同,Chla、Chlb和ChlT都表现出低．高一低的趋势,而且不同处理间变化不同步。不同处理间比较,O3处理的植株叶绿素含量下降最为明显,其次是复合处理的影响,而CO2浓度倍增对提高叶片叶绿素含量有一定的作用。Chla/b呈下降趋势,受CO2倍增影响最明显,有利于提高作物的光合性能。     

Doubling the CO2 Concentration Enhanced the Activity of Carbohydrate-Metabolism Enzymes,Source Carbohydrate Production,Photoassimilate Transport,and Sink Strength for Opuntia ficus-indica

After exposure to a doubled CO2 concentration of 750 [mu]mol mol-1 air for about 3 months glucose and starch in the chlorenchyma of basal cladodes of Opuntia ficus-indica increased 175 and 57%, respectively, compared with the current CO2 concentration of 370 [mu]mol mol-1, but sucrose content was virtually unaffected. Doubling the CO2 concentration increased the nocturnal malate production in basal cladodes by 75%, inorganic phosphate (Pi) by 32%, soluble starch synthase activity by 30%, and sucrose-Pi synthase activity by 146%, but did not affect the activity of hexokinase. Doubling CO2 accelerated phloem transport of sucrose out of the basal cladodes, resulting in a 73% higher dry weight for the daughter cladodes. Doubling CO2 increased the glucose content in 14-d-old daughter cladodes by 167%, increased nocturnal malate production by 22%, decreased total amino acid content by 61%, and increased soluble starch synthase activity by 30% and sucrose synthase activity by 62%. No downward acclimation of photosynthesis during long-term exposure to elevated CO2 concentrations occurs for O. ficus-indica (M. Cui, P.M. Miller, P.S. Nobel [1993] Plant Physiol 103: 519-524; P.S. Nobel, A.A. Israel [1994] J Exp Bot 45: 295-303), consistent with its higher source capacity and sink strength than under current CO2. These changes apparently do not result in Pi limitation of photosynthesis or suppression of genes governing photosynthesis for this perennial Crassulacean acid metabolism species, as occur for some annual crops.     

Effects of carbohydrate accumulation on photosynthesis differ between sink and source leaves of Phaseolus vulgaris L

Accumulation of non-structural carbohydrate in leaves represses photosynthesis. However, the extent of repression should be different between sink leaves (sugar consumers) and source leaves (sugar exporters). We investigated the effects of carbohydrate accumulation on photosynthesis in the primary leaves of bean (Phaseolus vulgaris L.) during leaf expansion. To increase the carbohydrate content of the leaves, we supplied 20 mM sucrose solution to the roots for 5 d (sugar treatment). Plants supplied only with water and nutrients were used as controls. The carbohydrate contents, which are the sum of glucose, sucrose and starch, of the sugar-treated leaves were 1.5-3 times of those of the control leaves at all developmental stages. In the young sink leaves, the photosynthetic rate at saturating light and at an ambient CO2 concentration (A360) did not differ between the sugar-treated and control leaves. The A360 of sugar-treated source leaves gradually decreased relative to the control source leaves with leaf expansion. The initial slope of the A-Ci (CO2 concentration in the intercellular space) curve, and the Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) content per leaf area showed trends similar to that of A360. Differences in Amax between the treatments were slightly smaller than those in A360. These results indicate that the effect of carbohydrate accumulation on photosynthesis is significant in the source leaves, but not in the young sink leaves, and that the decrease in Rubisco content was the main cause of the carbohydrate repression of photosynthesis.     

Drought effect on nitrate reductase and sucrose-phosphate synthase activities in wheat (Triticum durum L.): role of leaf internal CO2

In order to study the impact of a decline of leaf internal CO(2) molar ratio on nitrate reductase (NR) and sucrose-phosphate synthase (SPS) activities, leaves of wheat (Triticum durum) were submitted to different treatments: slow or rapid dehydration and decline in ambient CO(2) concentration and abscisic acid (ABA) supply. In agreement with the literature, NR activity of slowly dehydrated leaves was inhibited by about 50% when net CO(2) assimilation (A(n)) decreased by 45%. NR activity of stressed leaves kept 4 h in air containing 5% CO(2) or after 2 d of re-watering was only partially restored. NR activity was slightly dependent on ambient CO(2) molar ratio, declining by 30% when non-stressed leaves were kept in CO(2)-free air for 4 h. The decline of NR activity after ABA supply (through the transpiration stream) and after rapid dehydration of non-stressed leaves was comparable with the decrease observed under low CO(2) treatment. Overall, these data suggest that a drought-induced decrease of the leaf internal CO(2) concentration is only part of the signal triggering the decline of NR activity. In disagreement with most of the literature, SPS activity increased during slow dehydration, being stimulated by 30% when A(n) declined by 40%. SPS activity of stressed leaves kept 4 h in air containing 5% CO(2) or 2 d after re-watering was slightly increased or unchanged, respectively. By contrast to NR activity, SPS activity of well-hydrated leaves was hardly affected by low CO(2). Increased SPS activity was mimicked, in non-stressed leaves, by a rapid dehydration within 4 h and by ABA fed through the transpiration stream. In durum wheat, the increase in SPS activity could be linked to ABA-based signalling during a drought stress.     

Respective and interactive effects of doubled CO2 and O3 concentration on membrane lipid peroxidation and antioxidative ability of soybean

Effects of doubled CO2 and O3 concentration on Soybean were studied in open-top chambers (OTC). Under doubled CO2 concentration, grain yield and biomass increased, the SOD activity, vitamin C (Vc) and carotenoid (Car) content also increased; Superoxide (O2-.) generating rate decreased, relative conductivity and malondialdehyde (MDA) content significantly declined.But under doubled O3 concentration, the SOD activity, Vc and Car contents declined, resulting in imbalance of activated-oxygen production, enhanced O2-. generating rate and accelerated process of lipid peroxidation and increase in MDA content and ion leakage of leaves. The final result was decreased grain yield and plant biomass. Interactive effects of doubled CO2 and O3 concentrations on soybean were mostly counteractive. However, the beneficial effects of concentration-doubled CO2 are more than compensate the negative effects imposed by doubled O3, and the latter in its turn partly counteracted the positive effects of the former.     

Respective and interactive effects of doubled CO2 and O3 concentration on membrane lipid peroxidation and antioxidative ability of soybean

Effects of doubled CO2 and O3 concentration on Soybean were studied in open-top chambers (OTC). Under doubled CO2 concentration, grain yield and biomass increased, the SOD activity, vitamin C (Vc) and carotenoid (Car) content also increased; Superoxide (O2-) generating rate decreased, relative conductivity and malondialdehyde (MDA) content significantly declined. But under doubled O3 concentration, the SOD activity, Vc and Car contents declined, resulting in imbalance of activated-oxygen production, enhanced O2- generating rate and accelerated process of lipid peroxidation and increase in MDA content and ion leakage of leaves. The final result was decreased grain yield and plant biomass. Interactive effects of doubled CO2 and O3 concentrations on soybean were mostly counteractive. However, the beneficial effects of concentration-doubled CO2 are more than compensate the negative effects imposed by doubled O3, and the latter in its turn partly counteracted the positive effects of the former.     

Photosynthetic Carbon Metabolism and Translocation in Wild-Type and Starch-Deficient Mutant Nicotiana sylvestris L

A high rate of daytime export of assimilated carbon from leaves of a starch-deficient mutant tobacco (Nicotiana sylvestris L.) was found to be a key factor that enabled shoots to grow at rates comparable to those in wild-type plants under a 14-h light period. Much of the newly fixed carbon that would be used for starch synthesis in leaves of wild-type plants was used instead for sucrose synthesis in the mutant. As a result, export doubled and accumulation of sucrose and hexoses increased markedly during the day in leaves of the mutant plants. The increased rate of export to sink leaves appeared to be responsible for the increase in the proportion of their growth that occurred during the day compared to wild-type plants. Daytime growth of source leaves also increased, presumably as a result of the increased accumulation of recently assimilated soluble carbon in the leaves. Even though starch accumulation did not occur in the leaves of mutant plants, nearly all the sugar that accumulated during the day was exported in the period of decreasing irradiance at the end of the diurnal light period. Changes in carbon allocation that occurred in leaves of wild-type and mutant plants near the end of the light period appeared to result from endogenous diurnal regulation associated with the day-night transition.     

Photoinhibition and Photoprotection in Ginkgo biloba leaves: Influence of Temperature,CO2 and O2

In midday ginkgo ( Ginkgo biloba L. ) leaves have to bear photon flux density over 1 400 μmol·m-2·s-l in combination with high temperatures around 35℃ at natural habitat. They show typical midday depression of stomatal conductance and of CO2 assimilation rate. The zeaxanthin changes with light intensity during the day. The influence of the combination of strong light and temperature on photoinhibition was also examined in the laboratory. A low CO2 internal conductance (31 mmol· m- 2·s- 1 ) was found in ginkgo leaves, which had been exposed to excessive light at temperature between 15 ℃ and 35 ℃ with reduced CO2 (80 μL·L-l) or oxygen (2%) for 2 h, causing a low CO2 concentration at the carboxylation site and a high proportion of photorespimtion. The ratio of electron transport to CO2 fixation was rather high in ginkgo ( 16 e- /CO2 at 25 ℃ ) as compared with other plants. It increased with temperature also in 2% 02 which could not be explained solely as due to change of photorespimtion. The reduction of oxygen in 340 or 80 μL·L- 1 CO2 had no effect on the extent of photoinhibition at all temperatures, which indicated that eleetron flow caused by photorespiration in excess light was negligible in protective effect in ginkgo leaves. However, a decreased CO2 coneentration increased photoinhibition, especially at high temperature. It is concluded that the dissipation of excessive excitation energy in the PS II antennae through the xanthophyll cycle may be the major protective mechanism to preventing from the deteriorated effects of strong light in ginkgo leaves.     

不同CO2浓度下渗透胁迫对小麦膜伤害的影响

研究了常规CO     

厚壁毛竹光合作用对CO_2浓度倍增的短期响应

采用Li-6400P光合测定仪对比测定了大气CO2浓度和短期CO2浓度倍增下不同季节厚壁毛竹的光合特性,结果表明:CO2浓度加倍促使最大净光合速率、净光合速率、水分利用率、光合量子效率和光饱和点升高,年平均增幅分别为62.79%、48.74%、94.41%、8.70%和16.67%;CO2浓度加倍促使蒸腾速率、暗呼吸速率和光补偿点下降,年平均降幅分别为17.60%、37.25%和40.50%。不同季节厚壁毛竹光合生理特性参数在CO2浓度加倍后的增加幅度或降低幅度与叶片生理活性和气候变化密切相关。CO2浓度的倍增并未明显改变厚壁毛竹光合特性的季节变化规律,除光补偿点外,其它光合参数的季节大小顺序仍与大气CO2浓度下的相同。厚壁毛竹光合作用对短期CO2浓度升高的响应特征与C3植物光合作用对短期CO2浓度升高响应的普遍规律相符。     

Photosynthetic Responses to Light Intensity in Intact Leaves of Some Coastal Desert and Tropical Rain Forest Plant Species in Atmospheres with Different CO2 Concentrations

The photosynthetic responses to light (A/light response) at different CO2 concentration levels were studied in five coastal desert plant species (two C4 species and three C3 species) and five tropical rain forest plant species (all C3' s) using LI-6400 Portable Photosynthesis System. The measurements were carried out in the Coastal Desert and Tropical Rain Forest mesocosms of Biosphere 2 located in Oracle, Arizona, USA. All the species measured had been growing in Biosphere 2 under very high CO2 concentrations (1500～4000 μmol · mol-1) for about four and half years. The authors measured A/light response curves in intact leaves of different species under a series of CO2 concentrations, 350 to 1500 μmol ~ mol-1. Except for the C4 grass, Panicurn maximum, the initial slopes and convexity (0) of A/light curves of all the species increased with the elevation of CO2 concentration. For most C3 species the light compensation points (LCP) and light saturation points (LSP) had increased when CO2 concentrations were elevated, especialy the LSPs. But for the C4 species, changes in LCPs and LSPs were small. In all the C3 species and the C4 shrub, Atriplesc canescens, the apparent maximum quantum yield of CO2 fixation (Φm, app) and maximum assimilation rate (Amax) increased under elevated CO2. But both Φmapp and Amax in Panicum maximum (C4) decreased. The Amax in Biosphere 2 increased by 127 % when CO2 concentration was doubled (from 375 to 750 μmol · mol-1), and C4 species by 39%. Such great enhancement could possibly be due to the fact that the plants had developed under very high CO2 concentration and large growth rooms in Biosphere 2.     

C02倍增对渗透胁迫下小麦叶片抗氧化酶类及细胞程序性死亡的影响

经渗透胁迫后 ,CO2 倍增条件下小麦叶片的SOD、POX和CAT的活性均显著高于对照 ,上升或稳定时期较长 ;在渗透胁迫后期MDA含量和电解质泄露率增加较慢 ,显著低于对照 ;H2 O2 含量一直高于对照但进行PEG胁迫后增长较慢。CO2 倍增条件下 ,小麦细胞出现DNA梯的时间较晚而且持续的时间较长 ,DNA梯出现时抗氧化酶和H2 O2 处于相对稳定状态。结果表明在渗透胁迫下CO2 倍增使小麦的抗氧化能力增强从而减轻了对细胞膜和DNA的损伤 ,并且干旱条件下小麦的细胞程序性死亡可能是由于细胞内氧化过强所致     

An Approach to a Function of Photorespiration in C3 Plants

Intact attached leaves of wheat were illuminated at 2000 μmol m-2·s-1 in CO2-free gas for 3 hours, inhibition percentage of photosynthesis in these leaves by illumination was related lo oxygen concentration in the gas. (1) The damage to the leaves became less gradually when oxygen concentration rose from 0 to 10%. (2) Almost no damage occurred between 10%–50% O2. (3) The damage appeared again when oxygen concentration exceeded 50%. The duration of CO2 outburst of wheat leaves in CO2-free gas containing 8%–11% O2 was 0nly about 15–30 min. However, no photoinhibition could be observed under this condition. Oxygen also could prevent isolated chloroplasts from the damage by strong light. No matter what concentration of oxygen in CO2-free gas was during photoinhibition treatment, the photodamaged site was always in PSⅡ. It is concluded from the results that the way in which photoinhibition was alleviated by oxygen seems not only to be photorespiration, but also the other unknown mechanisms waich may play more important part in it.     

CO2和O3浓度倍增及其交互作用对大豆叶绿体超微结构的影响

应用透射电镜观察了模拟大气CO2和O3浓度倍增及其交互作用(开顶箱法)对大豆叶肉细胞叶绿体超微结构的影响。结果表明,CO2浓度倍增促进了大豆叶绿体的发育,内含淀粉粒积累明显增多、体积增大;叶绿体被膜保持完好;叶绿体基粒片层排列整齐,而O3浓度倍增抑制了叶绿体内淀粉粒的累积,并导致叶绿体被膜破碎,片层解体,严重地破坏了叶绿体的结构和功能CO2和O3浓度倍增的交互作用对叶绿体超微结构有不同程度的破坏,但二者浓度呈梯度增加对叶绿体的损害作用要大于二者浓度持续倍增对叶绿体的影响,进一步表明CO2正效应对O3负效应的补偿作用。     

The water-water cycle in leaves is not a major alternative electron sink for dissipation of excess excitation energy when CO(2) assimilation is restricted

Electron flux from water via photosystem II (PSII) and PSI to oxygen (water-water cycle) may provide a mechanism for dissipation of excess excitation energy in leaves when CO(2) assimilation is restricted. Mass spectrometry was used to measure O(2) uptake and evolution together with CO(2) uptake in leaves of French bean and maize at CO(2) concentrations saturating for photosynthesis and the CO(2) compensation point. In French bean at high CO(2) and low O(2) concentrations no significant water-water cycle activity was observed. At the CO(2) compensation point and 3% O(2) a low rate of water-water cycle activity was observed, which accounted for 30% of the linear electron flux from water. In maize leaves negligible water-water cycle activity was detected at the compensation point. During induction of photosynthesis in maize linear electron flux was considerably greater than CO(2) assimilation, but no significant water-water cycle activity was detected. Miscanthus × giganteus grown at chilling temperature also exhibited rates of linear electron transport considerably in excess of CO(2) assimilation; however, no significant water-water cycle activity was detected. Clearly the water-water cycle can operate in leaves under some conditions, but it does not act as a major sink for excess excitation energy when CO(2) assimilation is restricted.     

大气CO2浓度倍增和施氮对冬小麦光合及叶绿素荧光特性的影响

采用开顶式气室,通过土培盆栽实验研究了不同大气CO2浓度(背景空气浓度375μmol·mol-1和倍增浓度750μmol·mol-1)和氮素水平(不施氮和施氮0.25 g/kg)下两个冬小麦品种(小偃6号和小偃22)主要生育期(拔节、孕穗、扬花、灌浆期)叶片叶绿素含量和荧光动力学参数的变化.结果显示,与背景CO2浓度相比,在不施氮条件下大气CO2浓度倍增处理的小麦叶片出现明显的光合下调现象,而施氮时变化不明显;同时,CO2浓度倍增后小麦各主要生育期叶片叶绿素含量均有不同程度地下降,荧光参数初始荧光(F0)值明显提高,最大荧光(Fm)、可变荧光(Fv)、最大光能转换效率(Fv/Fm)和PSⅡ潜在活性(Fv/F0)值均显著降低.施氮可提高冬小麦各个时期叶片叶绿素含量、Fm、Fv、和Fv/F0值,降低F0值;不施氮条件下,大气CO2浓度倍增对冬小麦各主要生育时期叶绿素含量和荧光参数的影响明显,而施氮后影响微弱.研究表明,大气CO2浓度升高对冬小麦光合速率、叶绿素含量和光系统Ⅱ(PSⅡ)的光合电子传递和潜在活性具有一定抑制作用,通过施氮可以有效地缓解其负面效应.     

Response of respiration of soybean leaves grown at ambient and elevated carbon dioxide concentrations to day-to-day variation in light and temperature under field conditions

BACKGROUND AND AIMS: Respiration is an important component of plant carbon balance, but it remains uncertain how respiration will respond to increases in atmospheric carbon dioxide concentration, and there are few measurements of respiration for crop plants grown at elevated [CO(2)] under field conditions. The hypothesis that respiration of leaves of soybeans grown at elevated [CO(2)] is increased is tested; and the effects of photosynthesis and acclimation to temperature examined. METHODS: Net rates of carbon dioxide exchange were recorded every 10 min, 24 h per day for mature upper canopy leaves of soybeans grown in field plots at the current ambient [CO(2)] and at ambient plus 350 micromol mol(-1) [CO(2)] in open top chambers. Measurements were made on pairs of leaves from both [CO(2)] treatments on a total of 16 d during the middle of the growing seasons of two years. KEY RESULTS: Elevated [CO(2)] increased daytime net carbon dioxide fixation rates per unit of leaf area by an average of 48 %, but had no effect on night-time respiration expressed per unit of area, which averaged 53 mmol m(-2) d(-1) (1.4 micromol m(-2) s(-1)) for both the ambient and elevated [CO(2)] treatments. Leaf dry mass per unit of area was increased on average by 23 % by elevated [CO(2)], and respiration per unit of mass was significantly lower at elevated [CO(2)]. Respiration increased by a factor of 2.5 between 18 and 26 degrees C average night temperature, for both [CO(2)] treatments. CONCLUSIONS: These results do not support predictions that elevated [CO(2)] would increase respiration per unit of area by increasing photosynthesis or by increasing leaf mass per unit of area, nor the idea that acclimation of respiration to temperature would be rapid enough to make dark respiration insensitive to variation in temperature between nights.     

12CO2 emission from different metabolic pathways measured in illuminated and darkened C3 and C4 leaves at low,atmospheric and elevated CO2 concentration

The detection of 12CO2 emission from leaves in air containing 13CO2 allows simple and fast determination of the CO2 emitted by different sources, which are separated on the basis of their labelling velocity. This technique was exploited to investigate the controversial effect of CO2 concentration on mitochondrial respiration. The 12CO2 emission was measured in illuminated and darkened leaves of one C4 plant and three C3 plants maintained at low (30-50 ppm), atmospheric (350-400 ppm) and elevated (700-800 ppm) CO2 concentration. In C3 leaves, the 12CO2 emission in the light (Rd) was low at ambient CO2 and was further quenched in elevated CO2, when it was often only 20-30% of the 12CO2 emission in the dark, interpreted as the mitochondrial respiration in the dark (Rn). Rn was also reduced in elevated CO2. At low CO2, Rd was often 70-80% of Rn, and a burst of 12CO2 was observed on darkening leaves of Mentha sativa and Phragmites australis after exposure for 4 min to 13CO2 in the light. The burst was partially removed at low oxygen and was never observed in C4 leaves, suggesting that it may be caused by incomplete labelling of the photorespiratory pool at low CO2. This pool may be low in sclerophyllous leaves, as in Quercus ilex where no burst was observed. Rd was inversely associated with photosynthesis, suggesting that the Rd/Rn ratio reflects the refixation of respiratory CO2 by photosynthesizing leaves rather than the inhibition of mitochondrial respiration in the light, and that CO2 produced by mitochondrial respiration in the light is mostly emitted at low CO2, and mostly refixed at elevated CO2. In the leaves of the C4 species Zea mays, the 12CO2 emission in the light also remained low at low CO2, suggesting efficient CO2 refixation associated with sustained photosynthesis in non-photorespiratory conditions. However, Rn was inhibited in CO2-free air, and the velocity of 12CO2 emission after darkening was inversely associated with the CO2 concentration. The emission may be modulated by the presence of post-illumination CO2 uptake deriving from temporary imbalance between C3 and C4 metabolism. These experiments suggest that this uptake lasts longer at low CO2 and that the imbalance is persistent once it has been generated by exposure to low CO2.     

Influence of CO(2)-HCO(3) Levels and pH on Growth, Succinate Production, and Enzyme Activities of Anaerobiospirillum succiniciproducens

Growth and succinate versus lactate production from glucose by Anaerobiospirillum succiniciproducens was regulated by the level of available carbon dioxide and culture pH. At pH 7.2, the generation time was almost doubled and extensive amounts of lactate were formed in comparison with growth at pH 6.2. The succinate yield and the yield of ATP per mole of glucose were significantly enhanced under excess-CO(2)-HCO(3) growth conditions and suggest that there exists a threshold level of CO(2) for enhanced succinate production in A. succiniciproducens. Glucose was metabolized via the Embden-Meyerhof-Parnas route, and phosphoenolpyruvate carboxykinase levels increased while lactate dehydrogenase and alcohol dehydrogenase levels decreased under excess-CO(2)-HCO(3) growth conditions. Kinetic analysis of succinate and lactate formation in continuous culture indicated that the growth rate-linked production rate coefficient (K) cells was much higher for succinate (7.2 versus 1.0 g/g of cells per h) while the non-growth-rate-related formation rate coefficient (K') was higher for lactate (1.1 versus 0.3 g/g of cells per h). The data indicate that A. succiniciproducens, unlike other succinate-producing anaerobes which also form propionate, can grow rapidly and form high final yields of succinate at pH 6.2 and with excess CO(2)-HCO(3) as a consequence of regulating electron sink metabolism.     

大气CO2浓度升高对香蕉光合作用及光合碳循环过程中叶氮分配的影响

生长在高CC2浓度(700±56μl