干出和沉水不同条件下羊栖菜光合作用碳源获得机制比较(英文)

经济海洋褐藻羊栖菜(Hizikia fusiforme(Harv.)Okamura)低潮时常常周期性地暴露于空气中。为了认识这种海藻在潮汐循环背景下的光合特征,对其在高潮沉水和低潮干出不同条件下的光合作用碳素获得机制进行了比较。沉水时,羊栖菜主要利用海水中HCO_3~-作为外源无机碳源驱动光合作用;而在干出条件下,其光合作用的主要碳源为空气中的CO_2。在这两种不同环境条件下,光合作用与pH值的关系不同:沉水状态时,羊栖菜在高pH值(10.0)下光合活性很弱;而在干出条件下,羊栖菜在高pH值时仍有较高的光合活性。然而,光合作用无论是在沉水还是在干出条件下,对外源碳源的获得都表现出对胞外碳酸酐酶(CA)强烈的依赖性,并且其光合速率都受周围环境中无机碳源水平的限制。此外,在沉水和干出两种环境条件下,羊栖菜光合作用都表现出对氧气的敏感性。这表明,在羊栖菜中,依赖胞外CA的碳源获得机制不能使细胞内CO_2浓度提高到阻碍其光呼吸的程度。增加空气中或海水中无机碳的浓度,能促进羊栖菜的光合作用,进而增加这种海藻的水产养殖产量。     

低潮干出状态下石莼的光合作用特性（简报）

在低潮时（即干出状态下）汕头广澳湾潮间带海藻石莼的光合速率和呼吸速率都有随水分损失增加而下降的趋势。PSⅡ光化学效率、表观量子产额、光饱和点、以及表观羧化效率都随水分损失增加而下降;而光补偿点、CO2补偿点则随水分损失增加而增高,低潮时的干出状态下空气中CO2浓度限制石莼的光合作用,如果大气CO2浓度升高,则会促进其暴露于空气中的光合作用。     

赤潮藻中肋骨条藻的光合作用对海水pH和N变化的响应

为探讨赤潮发生时中肋骨条藻 (Skeletonemacoatatum)的光合作用生理变化 ,研究了不同无机氮 (N)水平上 ,海水pH值升高对其胞外碳酸酐酶 (CA)和光合生理特性的影响。海水pH从 8.2升至 8.7时 ,中肋骨条藻胞外CA被诱导 ,细胞对无机碳的亲和力 (1/Km)提高 ;在pH8 7时 ,高N条件下的胞外CA活性是低N条件下的 3倍 ,1/Km 值也提高了 80 %。单位叶绿素a的最大净光合能力 (Pam)在不同pH和N水平上没有显著差异 ;但单位细胞的最大净光合能力 (Pcm)提高了 10 0 %。这些结果表明 ,赤潮发生时 ,中肋骨条藻通过启动无机碳浓缩机制 (CCM) ,提高细胞对无机碳利用效率 ,使其在低CO2 (高pH)环境下维持光合机构正常运行 ;充足的N源有利于提高CCM的效率 ,从而提高CO2 环境下的光合固碳能力。     

碳酸酐酶在中肋骨条藻光合作用中的作用

探讨了在正常空气条件下生长的中肋骨条藻(Skeletonema costatum)的碳酸酐酶(CA)在其光合固碳中的作用.在中肋骨条藻的胞内和胞外均有CA活性,但胞外CA活性很低.CA抑制剂AZ(乙酰唑磺胺)对中肋骨条藻的光合放氧速率没有明显影响,而CA抑制剂EZ(乙氧苯唑胺)对其光合放氧速率有强烈的抑制作用.EZ的抑制作用使细胞最大光合速率、饱和光强和无机碳亲和力下降,无机碳的补偿点和光呼吸提高,使强光下光抑制作用增强.这些结果表明:中肋骨条藻的胞外CA在其光合作用中所起的作用较小,而其胞内CA通过催化胞内碳库中的HCO-3快速转化成CO2,提高胞内CO2的有效供给,从而提高细胞光合固碳能力和对逆境(高O2、强光和低CO2)的适应能力.     

在水生与气生状态下石莼光合作用对无机碳的响应

潮间带海藻光合作用总是处于水生(高潮时)与气生(低潮时)两种连续变化的环境状态下进行.对汕头沿岸常见的潮间带海藻石莼(Ulva lactuca L.)在水生和气生不同状态下光合作用对无机碳的响应特性进行了比较研究.在水生状态下,现有海水中溶解性无机碳浓度能充分饱和(10 ℃和20 ℃时)或接近饱和(30 ℃时)石莼的光合作用;而在气生状态下,石莼光合作用受大气CO2浓度的限制,且这种限制作用在较高温度(20-30 ℃)下比在低温(10 ℃)下更严重.在10 ℃和20 ℃时,石莼在气生状态下比在水生状态下具有更高的碳饱和最大光合速率;而在30 ℃时,石莼在这两种状态下的碳饱和光合速率相似.石莼光合作用的Km (CO2)值在气生状态下比在水生状态下高;而在气生状态下石莼对CO2的表观光合导度远小于其在水生状态下的值.认为大气CO2浓度升高将通过促进石莼在气生状态下的光合作用而增加其初级生产力.     

低潮干出状态下潮间带海藻的某些光合生理特性

生长在潮间带的海藻总是处于低潮时干出和高潮时淹没于海水这两种状态的循环之中.本文介绍了低潮干出状态下潮间带海藻有关光合生理特性,并对今后的研究作了展望.     

在水生与气生状态下石莼光合作用对无机碳的响应

潮间带海藻光合作用总是处于水生 (高潮时 )与气生 (低潮时 )两种连续变化的环境状态下进行。对汕头沿岸常见的潮间带海藻石莼 (UlvalactucaL .)在水生和气生不同状态下光合作用对无机碳的响应特性进行了比较研究。在水生状态下 ,现有海水中溶解性无机碳浓度能充分饱和 (10℃和 2 0℃时 )或接近饱和 (30℃时 )石莼的光合作用 ;而在气生状态下 ,石莼光合作用受大气CO2 浓度的限制 ,且这种限制作用在较高温度 (2 0 - 30℃ )下比在低温(10℃ )下更严重。在 10℃和 2 0℃时 ,石莼在气生状态下比在水生状态下具有更高的碳饱和最大光合速率 ;而在30℃时 ,石莼在这两种状态下的碳饱和光合速率相似。石莼光合作用的Km(CO2 )值在气生状态下比在水生状态下高 ;而在气生状态下石莼对CO2 的表观光合导度远小于其在水生状态下的值。认为大气CO2 浓度升高将通过促进石莼在气生状态下的光合作用而增加其初级生产力。     

大气CO2升高和紫外辐射相互作用对羊栖菜生理特性的影响

为了研究经济海藻羊栖菜对大气CO2浓度增加与紫外辐射(UVR)相互作用的响应,设置两个CO2浓度(380μL/L和800μL/L)以及两种辐射处理,即PAR处理(滤除UV-A、UV-B,藻体仅接受可见光,400—700nm)和PAB处理(全波长辐射280—700nm)培养海藻,探讨了羊栖菜生长、光合作用、呼吸作用、光合色素含量、可溶性糖和蛋白以及硝酸还原酶活性的变化情况。结果表明高浓度CO2显著提高羊栖菜藻体的相对生长速率,并且紫外辐射的负面效应在高CO2处理下表现不显著。高CO2降低了藻体的光合作用速率,而UVR的负面效应和生长体现为一致性,但是羊栖菜的呼吸作用没有受到环境变化的明显影响。羊栖菜的光合色素叶绿素a和类胡萝卜素在高浓度CO2处理下明显降低,而UVR没有明显影响。环境因子对羊栖菜的可溶性糖没有影响,但是在高CO2和全波长辐射处理下,藻体可溶性蛋白的含量显著增加。同时高CO2明显提高了硝酸还原酶的活性,并且仅在高浓度CO2处理下藻体中UVR对其活性有抑制作用。CO2和UVR对羊栖菜的大多数生理特性存在明显的交互作用,在未来CO2浓度进一步增加的情况下,UVR的负面效应将会得到一定程度的缓解,这样有利于羊栖菜在养殖海区获得更高的产量。     

大气CO_2浓度升高对不同氮生长条件下的两种大型海藻光合作用的影响

以龙须菜和蛎菜两种大型海藻为试验材料,在室外自然条件下培养,设置常规CO2浓度(390μL·L-1)和高CO2浓度(800μL·L-1)空气两种通气条件、以及10和150μmol·L-1两种氮营养盐供应水平,以探讨大气CO2浓度升高对不同氮营养盐生长条件下海藻生长与光合特性的影响。结果表明:不管是高氮还是低氮的培养条件,大气CO2浓度升高都能促进这两种海藻的生长;在龙须菜中,这种生长促进作用在低氮培养条件下更高,而在蛎菜中这种生长促进作用在高氮培养条件下较高;短期海水中高CO2浓度能促进蛎菜和龙须菜的光合作用;长期高CO2浓度生长环境依然能维持龙须菜高的光合作用,但抑制蛎菜的光合作用。另外,不管培养液中CO2供应条件如何,氮加富均促进了龙须菜和蛎菜这两种海藻的光全和呼吸作用。     

贵州喀斯特森林三种植物对不同坡位环境的光合生理响应

该研究以贵州普定喀斯特森林中、下坡位生长的构树( Broussonetia papyrifera)、朴树( Celtis sinensis)和光滑悬钩子( Rubus tsangii)为材料,通过对碳酸酐酶( CA)活性、光合作用日变化、净光合速率对CO2与光的响应曲线、叶绿素荧光特性以及稳定碳同位素组成等指标的测定,进而对比分析三种植物不同的光合生理响应特性。结果表明：构树光合作用过程的无机碳源既可来自大气中的CO2,也可以在气孔部分闭合的情况下利用细胞内的HCO3－,下坡位的构树较高的CA活性使其利用HCO3－的效率会更高,并能在较低光强下具有较高的光能利用效率。这可能与下坡位的构树具有较高的CA活性有关,对下坡位具有更好的适应性。朴树光合无机碳的同化能力最低,且光合无机碳源较单一,主要利用大气CO2,其较慢的生长速率使其对无机碳的需求最低,且能保持较稳定的无机碳同化速率。相对来说,中坡位的朴树具有相对较高的净光合速率和光能利用效率,对中坡位表现出较好的适应性。光滑悬钩子主要利用大气中的CO2进行光合作用。中坡位的光滑悬钩子具有较强的光能利用效率,并表现出较高的净光合速率,光滑悬钩子对中坡位同样表现出较好的适应性。该研究结果为喀斯特生态脆弱区植被重建过程中树种的选择及合理配置提供了科学依据。     

COMPONENTS OF PHOTOSYNTHESIS IN THE INTERTIDAL SACCATE ALGA HALOSACCION AMERICANUM (RHODOPHYTA,PALMARIALES)1

Rates of photosynthesis for the intertidal saccate alga Halosaccion americanum Lee were determined under submersed and emersed conditions. By fitting the data to a hyperbolic tangent function, P _max was 4.08 mmol CO₂. m^?2. h^?1 and I_k was 116.4 μE. m^?2. s^?1. under submersed conditions. Under emersed conditions, P _max was 1.89 mmol CO₂. m^?2. h^?1 and I_k was 22.9 μE. m^?2. s^?1. Dark fixation represented 3.7% of P_max in submersed thalli, whereas it equalled 33.3% of P_max in emersed thalli. Photosynthetic uptake from the thallus cavity represented a significant source of carbon, achieving 68.8% of that from the atmosphere and 29.4% of that from seawater. Retained seawater also greatly reduced drying under emersed conditions. Experimental thalli lost 70.4% of their water after 120 min under desiccating conditions, whereas control thalli lost only 6.3%. Emersed photosynthetic rates were enhanced by desiccation, At times, rates for desiccated thalli were two times those of fully-hydrated ones. Only after water loss exceeded 47% did photosynthetic rates fall below fully-hydrated rates. Utilizing data from this study a model was constructed to determine total photosynthetic production of H. americanum over a single daylight period. These caluclations demonstrate that photosynthetic contributions from emersed photosynthesis and retained seawater are significant. Because production from all sources is almost equal, total photosynthesis over a single day does not change greatly regardless of the time spent in air or in water.     

Inorganic carbon uptake kinetics of the stream macrophyte Callitriche cophocarpa Sendt.

Photosynthetic carbon uptake of Callitriche cophocarpa Sendt. was examined in plants collected from six Danish streams and in plants grown under variable inorganic carbon conditions in the laboratory. Both field and laboratory plants showed a low affinity for inorganic carbon (CO₂ compensation points ranging from 0.7 to 22 μM, and K_0.5(CO₂) from 51 to 121 μM), consistent with C-3 photosynthesis and use of CO₂ alone. Variation in inorganic carbon uptake characteristics was low in both groups of plants. Only in laboratory-grown plants was a coupling found between carbon uptake and the inorganic carbon regime of the medium. The carbon extraction capacity, expressed as a percentage of the initial amount of dissolved inorganic carbon (DIC) assimilated in PH-drift experiments, increased from −1.4 to 11.8% with declining external carbon availability, and the initial slope of the CO₂ response curve increased from 6.4 to 15.3 g⁻¹ h⁻¹ dm³. The plasticity of the inorganic carbon uptake system of C. cophocarpa was very low compared to the plasticity observed for submerged macrophytes with accessory carbon uptake systems (i.e. HCO₃⁻ use or C-4 photosynthesis), suggesting that the plasticity of the C-3 photosynthetic apparatus as such is restricted. The low carbon affinity of C. cophocarpa indicates that this species depends on CO₂ oversaturation for a sufficient supply of CO₂ for photosynthesis and growth.     

Photosynthetic gas exchange under emersed conditions in eulittoral and normally submersed members of the Fucales and the Laminariales: interpretation in relation to C isotope ratio and N and water use efficiency

Summary Ten species of brown macroalgae (five eulittoral and one submersed species of the Fucales; four submersed species of the Laminariales) from a rocky shore at Arbroath, Scotland, were examined for characteristics of emersed photosynthesis in relation to the partial pressure of CO₂ and O₂. The five eulittoral species of the Fucaceae were approaching CO₂ saturation for light-saturated photosynthesis at normal air levels of CO₂ (35 Pa) in 21 kPa O₂. The normally submersed algae are further from CO₂ saturation under these conditions, especially in the case of the four members of the Laminariales. The rate of net photosynthesis in the Fucaceae is O₂-independent in the range 2–21 kPa O₂ over the entire range of CO₂ partial pressure tested (compensation up to 95 Pa). For the other five algae tested, net photosynthesis is slightly inhibited by O₂ at 21 kPa relative to 2 kPa over the entire range of CO₂ partial pressures tested (compensation up to 95 Pa). CO₂ compensation partial pressures are low (<0.5 Pa) for the Fucaceae and independent of O₂ in the range 2–42 kPa. For the other five algae, the CO₂ compensation partial pressure are higher, and increased with O₂ partial pressure in the range 2–42 kPa. These gas exchange data show that the Fucaceae exhibit more C₄-like characteristics of their photosynthetic physiology than do the other five species tested, although even the Laminariales and Halidrys siliquosa are not classic C₃ plants in their photosynthetic physiology. These data suggest that, in emersed conditions as well as in the previously reported work on submersed photosynthesis, a CO₂ concentrating mechanism is operating which, by energized transmembrane transport of inorganic C, accumulates CO₂ at the site of RUBISCO and, at least in part, suppresses the oxygenase activity. Work with added extracellular carbonic anhydrase (CA), and with a relatively membrane-impermeant inhibitor of the native extracellular CA activity (acetazolamide), suggests that, in emersed conditions as well as in the previously reported work on algae submersed in seawater at pH 8, HCO _inf3 ^sup– is the major inorganic C species entering the cell. At optimal hydration, the rate of emersed photosynthesis in air is not less than the rate of photosynthesis when submersed in seawater, at least for the Fucaceae. ¹³C ratios of organic C for the Fucaceae are slightly more negative than is the case for the other five algae; these data are consitent with substantial (half or more of the entering inorganic C) leakage of CO₂ from the accumulated pool, and with some contribution of atmospheric CO₂ to the organic C gain by the eulittoral algae. The predicted increase in N use efficiency of photosynthesis in the Fucaceae, with their more strongly developed CO₂ concentrating mechanism, is consistent with data on emersed, but not submersed, photosynthesis for the algae collected from the wild and thus at a poorly defined N status. The more C₄-like gas exchange charateristics of photosynthesis in the eulittoral Fucaceae may be important in increasing the water use efficiency of emersed photosynthesis from the limited capital of water available for transpiration by a haptophyte.     

蛋白核小球藻生长和无机碳利用对不同光照强度和CO2浓度的响应

为了探讨光照强度和CO₂浓度对蛋白核小球藻(Chlorella pyrenoidosa)生长、无机碳利用的复合效应, 丰富绿藻中无机碳浓缩机制的资料, 该文设置两种光照强度(40和120 µmol photons•m^-2•s^-1)和两种CO₂浓度(0.04%和0.16%)组合成4种条件, 比较了蛋白核小球藻生长、无机碳浓度、pH补偿点、光合放氧速率、碳酸酐酶(CA)活性和α-CA基因转录表达对这4种培养条件的响应。结果发现: 蛋白核小球藻在高光强高CO₂浓度组生长最快; 低光强高CO₂浓度组培养体系中总无机碳浓度为1163.3 µmol•L^-1, 显著高于其他3组; 高光强低CO₂浓度组藻的pH补偿点最高(9.8), 而低光强高CO₂浓度组藻的pH补偿点最低(8.6); 低光强高CO₂浓度组藻的最大光合速率(V_max)和最大光合速率一半时的无机碳浓度(K_0.5)最高, 分别是其他3组的1.28-1.91倍和1.61-2.00倍; 高光强低CO₂浓度组藻的胞外CA活性最高; 而低光强低CO₂浓度组藻的胞外α-CA基因表达量显著高于其他3组。以上结果表明低CO₂浓度可促进蛋白核小球藻的pH补偿点和无机碳亲和力的提高, 诱导胞外CA活性及α-CA基因的表达; 该藻主要以HCO₃^-为无机碳源, 其对无机碳的利用受光照的调节。     

水稻田稗草叶片光合作用对开放式空气CO2浓度增高(FACE)的适应

于分蘖、拔节和抽穗3个时期在空气CO₂浓度(380μmol·mol^-1)下测定稻田中稗草叶片的净光合速率(Pn),发现在开放式CO₂浓度增高(FACE)条件下生长的稗草叶片后2个时期的Pn显著低于普通空气中生长的对照,比对照下降约20%,说明FACE条件下稗草叶片光合作用对高CO₂浓度发生了明显的适应.同时,叶片的气孔导度(Gs)和胞间CO₂浓度(Ci)的下降更为明显.与对照相比,叶片可溶性蛋白含量明显降低,拔节期只有对照的62.4%;高CO₂浓度下生长的稗草叶片Rubisco含量也降低,分蘖期和拔节期分别为对照的87%和84%,但其差异未达到显著水平.可以认为,长期生长在高CO₂浓度下的C₄植物稗草叶片光合作用的适应是叶片气孔部分关闭和可溶性蛋白含量下降的结果.     

The quenching of chlorophyll a fluorescence as a consequence of the transport of inorganic carbon by the cyanobacterium Synechococcus UTEX 625

The chlorophyll a fluorescence yield of the cyanobacterium Synechococcus UTEX 625 decreased upon the initiation of inorganic carbon transport. The fluorescence yield recovered upon the depletion of inorganic carbon from the medium or upon the addition of DCMU. The inhibition of photosynthetic CO₂ fixation by iodoacetamide did not prevent this reduction of fluorescence yield. Similar results were obtained for both Na⁺-stimulated HCO₃⁻ transport and for the transport (presumably of CO₂) that is stimulated by carbonic anhydrase. A transient lowering of the fluorescence yield was also observed when cell suspensions were pulsed with CO₂. In cells not inhibited with iodoacetamide, a very close quantitative relationship existed between the net rate of O₂ evolution and the maximum extent of fluorescence quenching seen as a function of the inorganic carbon concentration. The fluorescence quenching, however, was not due to CO₂ fixation but rather to the transport of inorganic carbon or the accumulation of the internal pool of inorganic carbon. If quenching is due to the latter it is not surprising that the extent of quenching corresponds to the maximum rate of photosynthesis as the rate of photosynthesis also depends on the size of the internal pool. The results with DCMU suggest that the quenching is Q quenching and transport must provide a mechanism for the oxidation of Q other than CO₂ fixation.     

CARBONIC ANHYDRASE ACTIVITY IN THE BLOOM-FORMING DINOFLAGELLATE PERIDINIUM GATUNENSE

The response of carbonic anhydrase (CA) activity in Peridinium gatunense Nygaard, the natural bloom-forming dinoflagellate in Lake Kinneret, to diel and seasonal variations in environmental conditions was characterized under controlled laboratory experiments. Simulated diel cycles demonstrated large changes in the ambient concentration of dissolved CO₂ and parallel changes in CA activity. The CA activity depended on the total concentrations of inorganic carbon (C₁) and in particular on the dissolved CO₂. Lowering the C₁ concentrations resulted in a large increase in CA activity within several hours. Light and photosynthesis were both required for the induction of CA activity. Under CO₂ -limited conditions, the dependence of the photosynthetic rate on CA (estimated from the ratio of photosynthetic rates in the presence or absence of CA inhibitors) was greater in P. gatunense than in other eukaryotic microalgae. This points to the ecological significance of CA in photosynthetic carbon uptake mechanisms of a large, dominant alga in a natural ecosystem .     

Rate limiting factors in leaf photosynthesis. II. Electron transport

Increased scattering of a weak 535 nm measuring beam which indicates the light-dependent formation of a transthylakoid proton gradient in leaves was used to examine the role of the electron-transport chain in limiting photosynthetic carbon assimilation. The proton gradient is supported by electron flux and indicates thylakoid energization. In CO₂-free air, half saturation of thylakoid energization was observed at intensities of red light ranging from 2 to 50 W·m⁻² in different plant species. The differences were attributed to different carbohydrate availability for energy-consuming photorespiratory processes when external CO₂ was absent. Thylakoid energization of shade leaves (Asarum, Fagus) was saturated at lower light intensities than that of sun leaves (Phaseolus, Fagus). When photorespiratory carbohydrate oxidation was suppressed by decreasing the O₂ concentration from 21 to 2% in the absence of CO₂, thylakoid energization saturated at lower light intensities than in CO₂-free air. CO₂ decreased thylakoid energization particularly at low light intensities. Under high intensity illumination, however, thylakoid energization was remarkably high even in the presence of saturating CO₂. Apparently, electron transport was capable of maintaining the energy status of the photosynthetic apparatus at a high level even when photosynthetic carbon fluxes were maximal. This suggests that electron transport is less important in limiting photosynthesis than previously thought.     

水稻叶片光合作用对开放式空气CO2浓度增高(FACE)的响应与适应

利用便携式光合气体分析系统(LI-6400),比较测定了高CO₂浓度(FACE,free-airCO₂enrichment)和普通空气CO₂浓度下生长的水稻叶片的净光合速率、水分利用率、表观量子效率和RuBP羧化效率等光合参数.在各自生长CO₂浓度(380vs580μmol·mol^-1)下测定时,高CO₂浓度(580μmol·mol^-1)下生长的水稻叶片的净光合速率、碳同化的表观量子效率和水分利用率明显高于普通空气(380μmol·mol^-1)下生长的水稻叶片.但是,随着FACE处理时间的延长,高CO₂浓度对净光合速率的促进作用逐渐减小.在相同CO₂浓度下测定时,FACE条件下生长的水稻叶片净光合速率和羧化效率明显比普通空气下生长的对照低.尽管高CO₂浓度下生长的水稻叶片的气孔导度明显低于普通空气中生长的水稻叶片,但两者胞间CO₂浓度差异不显著,因此高CO₂浓度下生长的水稻叶片光合下调似乎不是由气孔导度降低造成的.