Cyanide-resistant respiration in photosynthetic organs of freshwater aquatic plants

The rate and sensitivity to inhibitors (KCN and salicylhydroxamic acid[SHAM]) of respiratory oxygen uptake has been investigated in photosynthetic organs of several freshwater aquatic plant species: six angiosperms, two bryophytes, and an alga. The oxygen uptake rates on a dry weight basis of angiosperm leaves were generally higher than those of the corresponding stems. Leaves also had a higher chlorophyll content than stems. Respiration of leaves and stems of aquatic angiosperms was generally cyanide-resistant, the percentage of resistance being higher than 50% with very few exceptions. The cyanide resistance of respiration of whole shoots of two aquatic bryophytes and an alga was lower and ranged between 25 and 50%. These results suggested that the photosynthetic tissues of aquatic plants have a considerable alternative pathway capacity. The angiosperm leaves generally showed the largest alternative path capacity. In all cases, the respiration rate of the aquatic plants studied was inhibited by SHAM alone by about 13 to 31%. These results were used for calculating the actual activities of the cytochrome and alternative pathways. These activities were generally higher in the leaves of angiosperms. The basal oxygen uptake rate of Myriophyllum spicatum leaves was not stimulated by sucrose, malate or glycine in the absence of the uncoupler carbonylcyanide-m-chlorophenylhydrazone (CCCP), but was greatly increased by CCCP, either in the presence or in the absence of substrates. These results suggest that respiration was limited by the adenylate system, and not by substrate availability. The increase in the respiratory rate by CCCP was due to a large increase in the activities of both the cytochrome and alternative pathways. The respiration rate of M. spicatum leaves in the presence of substrates was little inhibited by SHAM alone, but the SHAM-resistant rate (that is, the cytochrome path) was greatly stimulated by the further addition of CCCP. Similarly, the cyanide-resistant rate of O₂ uptake was also increased by the uncoupler.     

Relationship between photosynthetic and respiratory carbon metabolism in freshwater phytoplankton

Measurements of algal carbon metabolism in the light and the dark were conducted in (1) short-term (3-h) light and dark incubations, (2) a diel (24-h) experiment, and (3) a longer-term (4-d) carbon accumulation experiment to examine the relationship between photosynthetic rates, photosynthetic carbon metabolism in the light, and respiration and carbon metabolism in the ensuing dark period in natural assemblages of freshwater phytoplankton. High rates of photosynthesis and polysaccharide synthesis in the light were followed by high rates of respiration and polysaccharide utilization in the dark. Polysaccharide was the major respiratory substrate in the dark, and small molecular weight metabolites, lipids, and protein were less important sources of metabolic energy. The protein pool accumulated carbon during dark incubations, but more slowly than during active photosynthesis in the light. Because the intracellular macromolecular pools turn over at very different rates (polysaccharide > protein and lipid), patterns of short-term photosynthetic carbon metabolism are not necessarily indicative of the biochemical composition of the phytoplankton.     

曼陀罗光合特性研究

采用LI-6400型便携式光合测定仪对潜在能源植物曼陀罗(Datura stramonium L.)在6月份至9月份的光合特性指标(净光合速率、光合有效辐射强度和气孔导度)的日变化以及净光合速率和叶绿素含量的月平均值变化进行了研究,并采用非直角双曲线对曼陀罗叶片净光合速率的光响应曲线和C02响应曲线进行了拟合.结果表明:实验期间(6月份至9月份),光合有效辐射强度和曼陀罗叶片净光合速率的日变化均呈"单峰型",峰值出现在11:00左右;7月份的净光合速率峰值最高,为19.01μmol·m-2·s-1;气孔导度日变化呈"双峰型",最大峰值和次峰值分别出现在12:00和14:00.不同月份的净光合速率月平均值有极显著差异(P＜0.01),其中7月份的净光合速率月平均值最大,为9.41 μmol·m-2·s-1;不同月份叶绿素的月平均含量变化与净光合速率月平均值的变化相似,7月份叶绿素的月平均含量也最高,但叶绿素a、b及总叶绿素月平均含量有一定差异.曼陀罗叶片净光合速率的光响应曲线和CO2响应曲线相似,在光合有效辐射强度和CO2浓度较低的条件下呈线性升高,至饱和点后缓慢升高并趋于稳定;曼陀罗叶片的光补偿点为22.42 μmol·m-2·s-1,光饱和点为689.26 μmol·m-2·s-1;CO2补偿点为74.06μmol·mol-1,CO2饱和点为1 331.97μmol·mol-1.研究结果说明,曼陀罗为具有一定耐阴能力的阳性植物,但CO2同化能力较弱.     

A freshwater cyanophage whose genome indicates close relationships to photosynthetic marine cyanomyophages

Bacteriophage S-CRM01 has been isolated from a freshwater strain of Synechococcus and shown to be present in the upper Klamath River valley in northern California and Oregon. The genome of this lytic T4-like phage has a 178,563 bp circular genetic map with 297 predicted protein-coding genes and 33 tRNA genes that represent all 20-amino-acid specificities. Analyses based on gene sequence and gene content indicate a close phylogenetic relationship to the 'photosynthetic' marine cyanomyophages infecting Synechococcus and Prochlorococcus. Such relatedness suggests that freshwater and marine phages can draw on a common gene pool. The genome can be considered as being comprised of three regions. Region 1 is populated predominantly with structural genes, recognized as such by homology to other T4-like phages and by identification in a proteomic analysis of purified virions. Region 2 contains most of the genes with roles in replication, recombination, nucleotide metabolism and regulation of gene expression, as well as 5 of the 6 signature genes of the photosynthetic cyanomyophages (hli03, hsp20, mazG, phoH and psbA; cobS is present in Region 3). Much of Regions 1 and 2 are syntenic with marine cyanomyophage genomes, except that a segment encompassing Region 2 is inverted. Region 3 contains a high proportion (85%) of genes that are unique to S-CRM01, as well as most of the tRNA genes. Regions 1 and 2 contain many predicted late promoters, with a combination of CTAAATA and ATAAATA core sequences. Two predicted genes that are unusual in phage genomes are homologues of cellular spoT and nusG.     

温光型核雄不育小麦育性转换的温度敏感期和临界温度研究

多年人工气候箱和田间分期播种试验表明,小麦温光型隐性核雄不育两用系C49S育性温度敏感期较长,从花粉母细胞形成期到成熟花粉期都有一定程度的敏感性,其中最敏感的时期有两个,即花粉母细胞减数分裂期和小孢子中期,当减数分裂期温度与小孢子中期温度均较低时,C49S表现为高度不育,当其温度均较高时,C49S表现为高度可育;C49S高度不育的临界温度是减数分裂期平均最低温度(Tmin₁)、小孢子中期平均温度(T₂)和平均最低温度(Tmin₂),分别为8.5℃、13.5℃和10.5℃;C49S高度可育的临界温度是Tmin₁11.5℃、T₂15.0℃、Tmin₂12.5℃;对温光型核雄不育两用系在小麦杂种优势利用中的应用价值、条件及风险进行了综合评价.     

Seasonal and spatial patterns in phytoplankton photosynthetic parameters in a tidal freshwater river

The photosynthetic response to irradiance wasquantified for phytoplankton from the tidalfreshwater Potomac River biweekly to monthly over aperiod of six years. Samples were collected from twoshallow embayments and portions of the deeper rivermainstem. Photosynthetic rate was measured in thelaboratory at in situ temperature over a range ofirradiance levels and photosynthetic parameters werecalculated using nonlinear regression.P^B _max,the maximum photosynthetic ratestandardized to chlorophyll a, increased withtemperature up to 25 °C with a Q₁₀ of 2.02. Above 25 °C, P^B _max was essentiallyconstant with temperature. Lesser correlationbetween P^B _max and ambient irradiance couldbe explained by the correlation of irradiance withtemperature. , the slope of the P–I curve atlow light, was correlated with both ambientirradiance and temperature. Highest valueswere found in late summer when high temperature andintermediate ambient irradiance were observed. Spring and early summer were characterized by low. Despite low light penetration, I_k and values were indicative of sun limitationpossibly due to intermittent high light levelsexperienced during mixing. I_k showed a clearseasonal trend directly related to days from summersolstice. Spatial patterns were minimal except thatI_k was consistently lower in one shallowembayment than in the other two areas. Seasonalpatterns in photosynthetic parameters correspondedroughly to changes from a spring diatom populationto summer cyanobacterial assemblage.     

栲树冠层光合生理特性的空间异质性

森林冠层在能量传输、光合有效辐射和微气象等方面的差异可导致冠层光合生产力空间分布的变化.叶片光合生理特性在空间上的差异对精确估算森林冠层的初级生产力十分重要.本文以亚热带常绿阔叶林优势种---栲树(Castanopsis fargesii)为对象,研究叶片光合生理特性在冠层空间上的变化.结果表明:1)在垂直方向上,冠层北向叶的饱和光合速率(Amax)、光饱和点(LSP)和CO2羧化效率(CCE)均表现为上部>中部>底部,且依次平均降低19.4%、18.1%和37.1%;光补偿点(LCP)、光下暗呼吸(Rd)以及冠层南向叶的饱和光合速率、光饱和点和CO2羧化效率均表现为上部>底部>中部,上部比中部和底部高出12.3%~71.4%;表观量子效率(AQY)表现为底部>上部>中部,底部分别是顶部和中部叶的1.2和1.3倍;2)在水平方向上,冠层上部和底部南向叶的饱和光合速率、光饱和点和CO2羧化效率比北向叶高0.9%~31.5%;冠层中部北向叶的饱和光合速率等6个参数比南向叶高9.6%~63.2%.因此,在冠层水平上模拟和估算植物生产力时,必须考虑冠层光合生理特性的空间差异.     

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Different sources of nitrogen pose diverse effects to algal community, but the mechanism of inhibitory effects of nitrogen sources on freshwater diatoms is not fully understood. The purpose of this study was to compare biomass, photosynthetic activity, and morphological structure of three common freshwater diatoms (Cyclotella meneghiniana, Nitzschia sp., and Gomphonema parvulum) under different nitrogen sources (NO₃ ^? or NH₄ ⁺). The sorption characteristic of each diatom was investigated, and chlorophyll a (Chl-a) content and oxygen evolution rate were analyzed to investigate stress of different nitrogen sources on each diatom in the batch experiments. Ammonium lowered the growth rate of C. meneghiniana and Nitzschia sp. when it was supplied in addition to growth-saturating nitrate concentrations, suggesting a combined effect of inhibition of nitrate uptake and direct ammonium stress. Oxygen evolution rate of Nitzschia sp. showed that the direct ammonium stress on the photosynthetic activity can be alleviated by coexistence of nitrate in the nitrogen enriched treatment, but not for C. meneghiniana and G. parvulum, which may be caused by a different nitrate transporter system within algal cells. Transmission electron microscopy was used to assess the toxicity of ammonium on ultrastructural chloroplast of each diatom. Ultrastructural changes in chloroplasts showed undefined electron-dense granules and lipid droplets, but the membrane integrity of cell was maintained, suggesting an adaptation to adjustment to ammonia stress. Results showed that Cyclotella meneghiniana and Nitzschia sp. were more sensitive to ammonium stress than Gomphonema parvulum on growth, but the mechanism remains unclear.     

辽东栎冠层光合生理特性的空间异质性

冠层作为林木与环境因子相互作用最为直接的部分,研究冠层光合作用是分析森林生产力的基础。以北京东灵山辽东栎为对象,利用Li-6400便携式光合仪测定了不同冠层不同方向部位叶片的光合速率和光响应曲线,研究了叶片光合生理特性在冠层空间上的变化。结果表明：在不同冠层和不同方向上,饱和光合速率、光补偿点、光下暗呼吸和表观量子效率均存在差异,随着冠层下降以及从南至北,大多数光合生理特性指标表现出递减趋势。进一步的通径分析结果得出,光强、水气压亏缺、温度是影响不同层次光合速率的主要因子。冠层光合特性的空间异质性研究,对于在冠层水平上揭示植物固碳能力和估算植物生产力具有很重要的意义。     

Fluorescence characteristics of a natural assemblage of freshwater picocyanobacteria

The fluorescence characteristics of a freshwater assemblageof picocyanobacteria weredetermined in a mesotrophic lake usingmicrospectrofluorometry. In Jack's Lake. Ontario. 72–98%of the assemblage was comprised of cells with a single excitationpeak for chlorophyll (Chl) a (emission at 680 nm) at 565 ±3)nm. theexcitation spectra for Chl a resembling the spectralcomposition of downwelling irradiance. The assemblage was, therefore,dominated by a single phycobiliproteinpigment type, similarto type 2 phycoerythrin (PE) marine Synechococcus strains. Theshape of excitation spectra did not change significantly withdepth down to 0.6% of incident irradiance or between samplingdates, although the relative intensity of the PE excitationpeak was generally greater for populations below the thermoclinecompared to surface populations during summer stratification.Two separate populations of PE-containing picocyanobacteria,distinguished based on their morphology and plane of division,could be further separated based on their emission spectra (usingblue excitation): a Synechocystis type cell (PE-Sys) consistentlyhad a more pronounced peak at 665 nm from allophycocyanin comparedto a Synechococcus (PE-Syn) type cell. In addition, the ratioof the PE to Chl a peak emissions was higher in PE-Sys and increasedsignificantly with depth below the thermocline. While nitrogenwas limiting in the lake in summer, experimental additions ofnitrogen did not significantly affect this ratio in surfacewater populations, but increased the ratio in PE-Syn populationsat the base of the photic zone. For surface assemblages of picocyanobacteria,high irradiance may be more-important in regulating fluorescencecharacteristics than nitrogen stress. ¹Deceased September 7, 1993     

台湾桤木引种的光合生理特性研究

以台湾桤木 Alnusformosana 引种2年生苗木为研究对象,探讨了台湾桤木的光合生理生态特性.结果表明: 1 叶片净光合速率 Pn 具有明显的日变化.中部叶Pn日变化在生长中期表现为双峰曲线型,高峰分别出现在9:00和15:00左右,峰值分别为15.03μmol·m-2·s-1和12.97μmol·m-2·s-1;在生长初期和末期为单峰曲线型.不同部位叶片Pn大小为:中部叶>顶部叶>基部叶. 2 不同部位叶片Pn表现出不同的季节变化特征.中部叶和顶部叶一年有两个高峰,高峰均出现在6月和8月;基部叶只有一个高峰,出现在6月.光合作用具有较广的温度适应范围.自然条件下叶片最大净光合速率为17.67μmol·m-2·s-1;人工条件下为20.2μmol·m-2·s-1,在新的环境条件下表现出较强的光合适应能力. 3 叶片LCP为33.32～67.47μmol·m-2·s-1,LSP为1332～1656μmol·m-2·s-1,具有较低的光补偿点和较高的光饱和点,表现出较强的弱光利用能力和强光利用潜力. 4 台湾桤木CO2补偿点为54.17～74.98μmol·mol-1,CO2饱和点在800μmol·mol-1左右;羧化效率为0.0270～0.0468.表现出较大光合作用潜力和较广的生存适应能力. 5 通径系数分析表明,Cond、Ci、Vpdl和RH是影响叶片光合速率变化最主要的直接作用因子.     

东北帽儿山地区白桦种群光-光合特性的比较研究

运用LI-6400光合作用测定系统,对东北帽儿山地区白桦(Betula platyphylla)种群的光-光合特性进行了比较研究.结果表明:白桦有性种群的实际光合能力和潜在光合能力均大于白桦无性种群(中生生境)(P＜0.05);中生生境白桦的光合能力大于湿生生境(有性种群)(P＜0.05);无论是有性种群还是无性种群,不同年龄(幼苗、幼树、成树)的白桦光合能力均以幼苗阶段最低且光补偿点最高(P＜0.05).     

遮荫条件下草莓的光合特性变化

对宝交早生和硕丰两个草莓品种遮荫处理后测定其光合特性变化结果表明,遮荫处理使两个草莓品种叶片光合速率显著降低,分别下降了20%和47%,而表观量子效率分别提高了13%和8%.叶片中叶绿素含量升高而可溶性蛋白含量显著降低.光系统Ⅱ电子传递活性(PSⅡ活性)分别下降了22.5%和53.7%.1,5二磷酸核酮糖羧化酶(Rubisco)活性分别降低了19.6%和35.3%.进一步讨论了草莓光饱和速率下降的生理基础.     

紫茎泽兰光合特性对生长环境光强的适应

测定了不同光强下生长的紫茎泽兰叶片最大净光合速率(Pmax)、叶绿素荧光参数、光合色素含量和比叶重(SLW),探讨了其光适应能力及生理生态学机制．强光下(100％相对光强)紫茎泽兰发生了轻度光抑制,Pmax、SLW、类胡萝卜素含量和日间热耗散升高,但热耗散能力没有提高．强光下紫茎泽兰通过：1)加强日间热耗散和活性氧清除能力以及光系统Ⅱ反应中心可逆失活来耗散过剩光能;2)增大P～以增加光能利用;3)提高SLW,降低单位干重叶绿素含量以减少光能吸收3个途径避免了光合机构光破坏．弱光下(36％、12．5％和4．5％相对光强)紫茎泽兰日间热耗散很小,SLW降低,但P～较高,这有利于其增加光能吸收和利用效率．紫茎泽兰能在很大的光强范围内有效地维持光合系统正常运转,这可能是其表现较强入侵性的原因之一．     

地毯草的光合特性研究

地毯草是一种典型的暖季型草坪草。用Li 6400便携式光合分析仪测定地毯草的光合特性。地毯草的光合日进程呈单峰型,无"午休"现象且受非气孔限制,最大净光合速率出现在14∶00,变化趋势与光合有效辐射(PAR)、气温(Ta)、蒸腾速率(Tr)等因子相同,与空气相对湿度(RH)、胞间CO2浓度(Ci)等相反;其光饱合点超过2000μmol.m 2s 1,最大净光合速率达22μmol.m 2s 1,暗呼吸速率为1.34μmol.m 2s 1,CO2补偿点为0.97μmol.mol 1,光补偿点为22.2μmol.m 2s 1,羧化效率为0.2539μmol.m 2s 1,表观光量子效率高达0.0592μmol.mol 1;表明地毯草是一种具有较强耐荫性的C4型阳性的暖季型草坪草,除了在园林中可以广泛用作草坪地被外还可以在一些较荫湿的特殊地带作为绿化和防护之用。     

The photosynthetic characteristics of papyrus in a tropical swamp

Summary Photosynthesis and transpiration was measured in the large emergent C₄ sedge Cyperus papyrus (papyrus) which occupies wide areas of wetland on the African continent. The maximum observed value of net assimilation was 35 mol CO₂ m^-2 s^-1 at full sunlight but light saturation of photosynthesis did not occur. The quantum yield of photosynthesis obtained from the initial slope of the light response curves (0.06 mol mol^-1 incident light) was relatively high and close to previously recorded values for some C₄ grasses. Measurements made over two days showed that stomatal conductance was sensitive to the ambient air vapour pressure deficit (VPD) and was consistently lower on the day when VPD's were higher. There was, however, no marked midday closure of the stomata. Photosynthesis was also reduced on the day when VPD's were higher. The relationship between net photosynthesis and stomatal conductance was close to linear over the range of measurement conditions, with the result that intercellular CO₂ concentrations (C _i ) did not vary markedly. There was some evidence that C _i decreased at high VPD's. The regulation of stomatal movement in papyrus appears to minimise excessive water loss while not severely limiting photosynthesis. The significance of this strategy for a wetland species with plentiful supplies of water is discussed.     

胡萝卜光自养型愈伤组织的诱导培养及其光合特性

经诱导得到胡萝卜光自养型愈伤组织。以叶绿素为单位计算,获得的光自养型愈伤组织的光合活力达到甚至超过了整体植株叶片水平。同时测定愈伤组织光自养过程中光合特性的变化,结果表明其叶绿素含量逐渐上升、暗呼吸速率和Ch1a/Ch1b比值逐渐下降。并且用电子显微镜观察到愈伤组织中叶绿体结构逐渐发育的过程。