Kinetic Mechanisms of Biological Regulation in Photosynthetic Organisms

Principles of regulation on different levels of photosynthetic apparatus are discussed. Mathematical models of isolated photosynthetic reaction centers and general system of energy transduction in chloroplast are developed. A general approach to model these complex metabolic systems is suggested. Regulatory mechanisms in plant cell are correlated with the different patterns of fluorescence induction curve at different internal physiological states of the cells and external (environmental) conditions. Light regulation inside photosynthetic reaction centers, diffusion processes in thylakoid membrane, generation of transmembrane electrochemical potential, coupling with processes of CO₂ fixation in Calvin Cycle are considered as stages of control of energy transformation in chloroplasts in their connection with kinetic patterns of fluorescence induction curves and other spectrophotometric data.     

The Effects of Increased Illumination and Shading on the Low-Light-Induced Decline in Photosynthesis in Cotton Leaves

An experiment was carried out to study whether low-light-induced damage to the photosynthetic system in leaves of cotton (Gossypium hirsutum cv. Deltapine) which are below the compensation point in the canopy can be arrested and reversed by increased illumination. In addition it was intended to find out whether the photosynthetic system in leaves of shade plants show a greater resistance to low-light-induced damage than leaves of plants from more exposed habitats. The plants were grown at high density, and increased illumination to the shade leaves in the canopy was achieved by thinning the stand. Thinning was carried out at two stages and its effects on the decline in the photosynthetic capacity of the 4th leaf were followed. An early thinning was carried out shortly after the 4th leaf dropped below the compensation point and a late thinning 2 weeks later. Comparison was also made between the low-light-induced damage to the photosynthetic capacity of the 4th leaf in plants grown under two light regimes during the progressive increase in self-shading of the 4th leaf within the canopy. It was observed that both types of thinning arrested the low-light-induced damage to the photosynthetic system in shade leaves. The decline in photosynthetic capacity of the 4th leaf was stopped after both early and late thinning. The dry weight of the shoot system in the early and late thinned plants was not significantly different. It was double that of the control plants. The plants thinned early did not have higher shoot weight than the late thinned plants since there was a rapid shedding of flowers and fruits after early thinning. The 4th leaf in the early thinned plants showed a 30% increase in chlorophyll content and dry weight per unit leaf area. It is suggested that shedding of flowers and fruits, and increases in chlorophyll and dry weight per unit leaf area in the early thinned plants were caused by a change in the hormonal balance of the plants. The photosynthetic system in leaves of shade plants showed a greater resistance to damage by low light intensity than the photosynthetic system in leaves of plants grown at higher light intensities.     

Employing Rhodobacter sphaeroides to functionally express and purify human G protein-coupled receptors

G protein-coupled receptors (GPCRs) represent the largest class of cell surface receptors and play crucial roles in many cellular and physiological processes. Functional production of recombinant GPCRs is one of the main bottlenecks to obtaining structural information. Here, we report the use of a novel bacterial expression system based on the photosynthetic bacterium Rhodobacter sphaeroides for the production of human recombinant GPCRs. The advantage of employing R. sphaeroides as a host lies in the fact that it provides much more membrane surface per cell compared to other typical expression hosts. The system was tailored to overexpress recombinant receptors under the control of the moderately strong and highly regulated superoperonic photosynthetic promoter pufQ. We tested this system for the expression of some class A GPCRs, namely, the human adenosine A2a receptor (A2aR), the human angiotensin AT1a receptor (AT1aR) and the human bradykinin B2 receptor (B2R). Several different constructs were examined and functional production of the recombinant receptors was achieved. The best-expressed receptor, AT1aR, was solubilized and affinity-purified. To the best of our knowledge, this is the first report of successful use of a bacterial host--R. sphaeroides--to produce functional recombinant GPCRs under the control of a photosynthetic gene promoter.     

锌胁迫对两种柑橘幼苗光合特性日变化及其相关性的影响

通过砂培试验,采用C I-340型便携式光合测定系统研究了不同锌处理（0.05mg/L Zn为对照,0.5mg/L Zn为锌过量,0mg/L Zn为锌缺乏）对‘不知火’和‘椪柑’幼苗叶片光合特性日变化及其相关性的影响。结果表明,在锌胁迫条件下,‘不知火’叶片的净光合速率（Pn）日变化呈单峰曲线,对照为双峰曲线,而‘椪柑’与对照呈现相似的单峰型变化,且锌胁迫下两者平均的Pn均显著低于对照。简单相关分析表明,‘不知火’在锌胁迫下叶片Pn与光合有效辐射（PAR）、蒸腾速率（Tr）均呈显著的正相关,其对照Pn与各因子之间并无显著相关性,各锌处理下的‘椪柑’叶片Pn均与Gs呈显著正相关。逐步多元回归的分析结果与简单相关分析结果存在出入。还就锌胁迫对两品种柑橘的光合特性及其相关性的影响进行了讨论。     

Principles of redox control in photosynthesis gene expression

Light is one of the most important environmental factors influencing gene expression in photosynthetic organisms. In particular, genes for components of the photosynthetic machinery show light-dependent expression. In recent years, it has become clear that photosynthesis itself contributes important signals to this light control of gene expression by means of changes in the reduction/oxidation (redox) state of signalling molecules. Such changes in redox state are induced by changes in quality and quantity of the incident light. Redox signalling mechanisms therefore provide photosynthesis with the possibility of acclimational changes in the structure of the photosynthetic apparatus via a feedback control of photosynthesis gene expression. The great variety of these signalling mechanisms is summarised under the term 'redox control'. In some cases, oxygen acts as a different environmental, light-independent stimulus of photosynthetic gene expression, providing an additional redox signal and a different kind of redox control. In this review, we summarise present knowledge about such redox control mechanisms and analyse common properties as well as differences in the various signalling pathways. We suggest that there is an urgent need for a clear distinction between different kinds of redox control. Accordingly, we propose a categorisation into perceptional and transductional redox control. These categories are defined and examples given. The generalisation and comparability of results obtained in different physiological test systems and species are critically discussed.     

A Study on Ultrastructure,Development and Function of Plastids of Cuscuta australis R.Br

This paper deals with the distribution, category, ultrastructure and lammelar changes ofplastids in the stem of the dodder at four development stages. The qualitative assay wasmade oil the photosynthetic capacity of each period with spectrofluorimeter. The results are asfollows: The dodder is a semi-parasitic plant because it contains chlorophyll and chloroplasts whichare capable of photosynthesis. Chloroplasts exist only in phloem parenchyma, and containwell developed lammelar system during the development of haustoria. In this plant, the lammelar system has a rather unusual arrangement, similar to that of semi-parasite Viscum albumbut different from that of the typical seed plants. “Green amyloplasts” (GA) were observedin cortical parenchyma. The photosynthetic and parasitic ability of the dodder is the strongestin the seedling stage when the best effective control on dodder can be obtained.     

施氮对不同抗旱性冬小麦叶片光合与呼吸的调控

在大田条件下对两个不同抗旱特性的冬小麦品种全生育期叶片光合气体交换参数、光合色素含量和呼吸值及其对氮素水平的响应进行了研究.结果表明,施氮180 kg·hm^-2处理旱地品种叶片气孔导度、总光合色素含量、光合速率较不施氮处理在全生育期分别提高了43.75%、18.54%和49.66%,水地品种分别提高了12.12%、20.88%和29.25%;而旱地品种总呼吸速率降低了4.8%,水地品种降低了4.5%.适量施氮,增强了小麦叶片的气体交换能力,提高了光合色素含量,并降低了呼吸速率,从而提高了小麦叶片光合碳同化能力.小麦品种间光合的差异主要由非气孔因素引起.旱地品种呼吸速率较低,吸收的光能较多地用于光合碳同化作用.不施氮处理叶片光合速率较高的生育时期其呼吸速率也高,而施氮处理叶片光合速率高的生育时期呼吸值较低.施氮增加了光能向光合碳同化方向的分配.施氮对提高冬小麦抗旱能力有积极作用,其机理在于氮素改善了叶片气体交换状况,提高了光合色素含量,并优化了叶片对光能吸收的分配.     

Light and the correlation of chloroplast development and coupling of phosphorylation to electron transport

Coupling of phosphorylation to electron transport was examined by measuring the photosynthetic control ratio for broken wheat plastids isolated from seedlings at different greening stages. The photosynthetic control ratio progressively increased during greening and tight coupling was noted after granal stacking and thylakoid elongation. ADP impaired nonphosphorylating (state 2) electron transport rates of plastids at extremely early stages of greening and interfered with photosynthetic control measurements. Partially developed plastids exhibited low nonphosphorylating electron flow rates but did not exhibit high phosphorylating or uncoupled electron transport rates to the same extent as nearly developed plastids. Prolamellar body dispersal, primary thylakoid production, and the development of photosynthetic control were stimulated equally by 48 minutes of low irradiance, in cycles of 2 minutes every 2 hours, or by 9 hours of continuous light of moderate irradiance. Wheat plastids that greened for 6 hours in continuous light of moderate intensity did not exhibit photosynthetic control or much differentiation beyond the etioplast stage. It is concluded that plastid differentiation and the development of photosynthetic control early in greening under continuous light were limited by developmental time (dark time) rather than by either light intensity or duration.     

光合细菌对小麦生长和光合功能的影响

【目的】探明光合细菌对小麦生长、产量及光合功能的影响。【方法】以尧麦16为材料,在不同生长时期施用光合细菌,研究光合细菌对小麦生长、产量及光合功能的影响。【结果】光合细菌培养液的不同成分可提高小麦旗叶SPAD值、光合速率及干物质积累。拔节期施用后,混合菌液对叶片SPAD含量促进作用最大,较不施用对照提高33.6%,小麦干物质积累较对照增加25.7%,单株籽粒重量增效为14.3%。单菌株实验处理中沼泽红假单胞菌促进作用最强,干物质积累和单株籽粒重量较培养基稀释液对照增效均为13.1%。不同施用时期的结果表明沼泽红假单胞菌对灌浆期和拔节期小麦促进效应最强,其中静息细胞可延长叶片功能期,使光合产物持续增加;无细胞培养液通过促进小麦营养生长,进而提高小麦产量。【结论】光合细菌可促进小麦生长,有效提高小麦生育过程中相关光合功能;施用时期应为小麦拔节期和灌浆期;光合细菌对小麦生长和产量促进作用是静息细胞和代谢活性物质综合作用的结果。     

Structural and functional diversification of the light-harvesting complexes in photosynthetic eukaryotes

Eukaryotes acquired photosynthetic metabolism over a billion years ago, and during that time the light-harvesting antennae have undergone significant structural and functional divergence. The antenna systems are generally used to harvest and transfer excitation energy into the reaction centers to drive photosynthesis, but also have the dual role of energy dissipation. Phycobilisomes formed the first antenna system in oxygenic photoautotrophs, and this soluble protein complex continues to be the dominant antenna in extant cyanobacteria, glaucophytes, and red algae. However, phycobilisomes were lost multiple times during eukaryotic evolution in favor of a thylakoid membrane-integral light-harvesting complex (LHC) antenna system found in the majority of eukaryotic taxa. While photosynthesis spread across different eukaryotic kingdoms via endosymbiosis, the antenna systems underwent extensive modification as photosynthetic groups optimized their light-harvesting capacity and ability to acclimate to changing environmental conditions. This review discusses the different classes of LHCs within photosynthetic eukaryotes and examines LHC diversification in different groups in a structural and functional context.     

Physiological and biochemical responses of resistant and susceptible wheat to injury by Russian wheat aphid

We examined the physiological and biochemical responses of resistant ('Halt' and 'Prairie Red') and susceptible ('TAM 107') wheat, Triticum aestivum L., to injury by the Russian wheat aphid, Diuraphis noxia (Mordvilko). Photosynthetic capacity was evaluated by measuring assimilation/internal CO2 (A/Ci) curves, chlorophyll fluorescence, chlorophyll, and nonstructural carbohydrate content. Total protein and peroxidase specific activity also were determined. No significant differences were detected in chlorophyll concentration between aphid-infested and control TAM 107 plants. The aphid-infested resistant cultivars had similar or significantly higher chlorophyll concentrations compared with their respective control plants. Measurements over time showed that infested Halt plants had delays in photosynthetic senescence, Prairie Red plants had photosynthetic rate changes that were similar to control plants, and TAM 107 plants displayed accelerated photosynthetic senescence patterns. The photochemical and nonphotochemical quenching coefficients were significantly higher in infested Halt plants compared with their respective control plants on day 3. Infested TAM 107 plants had significantly higher photochemical quenching compared with control plants at all times evaluated, and they had significantly higher nonphotochemical quenching on day 3. Throughout the experiment, infested Prairie Red plants exhibited photochemical and nonphotochemical quenching coefficient values that were not significantly different from control plants. Total protein content was not significantly different between aphid-infested and control plants for all cultivars. Differences between physiological responses of infested susceptible and resistant cultivars, particularly temporal changes in photosynthetic activity, imply that resistant Halt and Prairie Red wheat tolerate some impacts of aphid injury on photosynthetic integrity.     

Relationship between salt tolerance and photosynthetic machinery performance in citrus

In citrus, salt stress has been related to the build up of chloride ions in plant tissues that affect photosynthesis, growth and yield. We investigated the effects of salt stress on the stability of the photosynthetic machinery with respect to the relative salt tolerance of different citrus genotypes including: Swingle Citrumelo, Carrizo citrange, C35 citrange, Cleopatra mandarin and Forner-Alcaide #5. Under identical salt-stress conditions, Forner-Alcaide #5 and Cleopatra mandarin accumulated less chloride ions in leaves than the other genotypes and showed a better plant performance. Chlorophyll fluorescence parameters indicated severe impairments of photosynthetic activity in salt-sensitive Citrumelo and citranges but Cleopatra and Forner-Alcaide #5 were less affected. In addition, differences in photosynthetic responses between these two moderately tolerant genotypes suggested different strategies to cope with salinity. The high tolerance to salinity shown by Forner-Alcaide #5 can be associated to the ability of keeping an active photosynthetic system at elevated saline conditions whereas the tolerance of Cleopatra was linked to rapid reductions of net photosynthetic rate, stomatal conductance, performance of PSII and photosynthetic efficiency.     

遮荫处理对不同苗龄交让木的生长和光合特性的影响

运用生理生态研究方法,选取不同苗龄(二年生和五年生)的交让木的幼苗,对其光合色素、光合特性和株高增量等指标进行测试分析。结果表明,遮荫后二年生和五年生交让木的叶绿素和类乎萝卜素含量上升,Chl.a/Chl.b下降,光饱和点和补偿点下降。和对照的全光照条件相比,二年生交让木在遮荫处理下株高增量较大,最大净光合速率较高,光合优势明显;而五年生交让木表现相反趋势。揭示了不同苗龄交让木的生长及光合特性,为其科学栽培管理措施的制定提供了理论依据。     

间作对氮调控玉米光合速率和光合氮利用效率的影响

研究间作后作物光合碳同化和光合氮利用效率(PNUE)对氮投入的响应, 对阐释间作产量优势的氮调控效应, 指导间作氮肥管理有重要意义。本研究设置玉米(Zea mays)单作、玉米间作两种种植模式的4个氮水平(N0, 0 kg·hm ^-2; N1, 125 kg·hm ^-2; N2, 250 kg·hm ^-2; N3, 375 kg·hm ^-2), 分析间作与施氮量对玉米叶片特征、光合参数、PNUE和产量的影响。结果表明: 与单作相比, 间作显著增加玉米叶片的叶干质量和比叶质量; 各施氮水平(除N3)下, 间作中靠近马铃薯(Solanum tuberosum)侧的玉米叶面积均显著高于单作玉米。单间作对比发现, 间作提高了玉米光饱和点和暗呼吸速率。单作、间作靠玉米侧(I-M)、间作靠马铃薯侧(I-P)的玉米PNUE均随施氮量增加而降低, 降幅以I-P最大; 施氮量低于250 kg·hm ^-2时, 相同施氮量下的玉米PNUE和净光合速率(P_n)均以I-P最高, I-M和单作次之。间作显著提高了玉米产量(土地当量比>1)。该研究中当施氮量≤250 kg·hm ^-2时, 间作I-P的玉米叶片P_n和PNUE显著提高可能是间作玉米产量提高的重要原因。     

Effects of intercropping on photosynthetic rate and net photosynthetic nitrogen use efficiency of maize under nitrogen addition

研究间作后作物光合碳同化和光合氮利用效率(PNUE)对氮投入的响应, 对阐释间作产量优势的氮调控效应, 指导间作氮肥管理有重要意义。本研究设置玉米(Zea mays)单作、玉米间作两种种植模式的4个氮水平(N0, 0 kg·hm ^-2; N1, 125 kg·hm ^-2; N2, 250 kg·hm ^-2; N3, 375 kg·hm ^-2), 分析间作与施氮量对玉米叶片特征、光合参数、PNUE和产量的影响。结果表明: 与单作相比, 间作显著增加玉米叶片的叶干质量和比叶质量; 各施氮水平(除N3)下, 间作中靠近马铃薯(Solanum tuberosum)侧的玉米叶面积均显著高于单作玉米。单间作对比发现, 间作提高了玉米光饱和点和暗呼吸速率。单作、间作靠玉米侧(I-M)、间作靠马铃薯侧(I-P)的玉米PNUE均随施氮量增加而降低, 降幅以I-P最大; 施氮量低于250 kg·hm ^-2时, 相同施氮量下的玉米PNUE和净光合速率(P_n)均以I-P最高, I-M和单作次之。间作显著提高了玉米产量(土地当量比>1)。该研究中当施氮量≤250 kg·hm ^-2时, 间作I-P的玉米叶片P_n和PNUE显著提高可能是间作玉米产量提高的重要原因。     

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。     

不同施肥条件下冷、暖型小麦旗叶光合生理特性的研究

以2类4个小麦品种为试验材料,通过田间小区试验,比较了灌浆结实期冷、暖型小麦在不施肥(CK)、单施磷肥(P)、单施氮肥(N)和氮磷配施(NP)等4种施肥条件下旗叶的光合生理特性。结果表明,不同施肥条件下,冷型小麦的旗叶叶面积、叶绿素含量、可溶性蛋白质含量及净光合速率均高于暖型小麦。其中,在不施肥和单施磷肥条件下,两类小麦之间各项生理指标的差异均达显著或极显著水平;在施用氮肥(单施氮肥和氮磷配施)条件下,两类小麦之间的差异有所减小,但冷型小麦仍然高于暖型小麦。冷型小麦旗叶优良的光合生理特性具有不随施肥条件的改变而发生根本性变化的特点,对土壤肥力状况有较强的适应性;而暖型小麦对土壤氮素营养要求较高。     

微生态制剂对海水养殖系统硝化功能建立过程的影响

比较分析投加不同微生态制剂的海水养殖系统硝化功能建立的过程,为实际应用提供依据。利用海水素构建4个海水养殖系统,通过投加硝化细菌、光合细菌、枯草芽胞杆菌3种微生态制剂以及纤维毛球作为生物膜载体,比较分析不同养殖系统硝化功能的建立过程及硝化强度差异。投加硝化细菌+光合细菌和硝化细菌+枯草芽胞杆菌系统硝化功能建立时间分别为108 h和96 h,氨氮初始质量浓度为6 mg/L时,氨氧化强度分别为1.69 mg/(L·d)和1.36 mg/(L·d);添加纤维毛球的生物膜系统与生物絮团系统硝化功能建立时间分别为96 h和120 h,氨氮初始质量浓度为6 mg/L时,氨氧化强度分别为1.36 mg/(L·d)和0.98 mg/(L·d);投加碳源系统和对照系统硝化功能建立时间分别为84 h和96 h,氨氮初始质量浓度为6 mg/L时,氨氧化强度分别为1.18 mg/(L·d)和1.36 mg/(L·d)。硝化细菌+枯草芽胞杆菌系统硝化功能建立时间更短,但系统硝化强度低于硝化细菌+光合细菌系统;生物膜系统硝化强度高于生物絮团系统且硝化功能建立更快;添加碳源能够加快系统硝化功能建立过程,但降低了硝化细菌+枯草芽胞杆菌系统的硝化强度。     

Photosynthetic productivity of conical helical tubular photobioreactors incorporating Chlorella sp. under various culture medium flow conditions

The characteristics of the flow of culture medium significantly affects the photosynthetic productivity of bioreactors incorporating microalgae. Therefore, in order to optimize the performance of a conical helical tubular photobioreactor (CHTP) designed to be useful in practical applications, we characterized the flow pattern of the culture medium through the reactor. The effects of medium flow conditions on the photosynthetic productivity of Chlorella sp. were investigated using several different CHTP units with 0.50-m2 installation areas which were designed to vary the direction and rate of flow driven by airlift. In addition, the performance of two- and four-unit systems constructed by combining individual CHTP units was evaluated. We found that when medium flowed from the bottom to the top of the photostage, it exhibited smoother flow of culture medium than when flowing from top to bottom, which led to higher photosynthetic productivity by the former. Consistent with theoretical calculations, varying the lengths of vertical flow passages caused flow rates to vary, and higher flow rates meant smoother circulation of medium and better photosynthetic performance. Flow of medium through a four-unit CHTP system was similar to that in single units, enabling a photosynthetic productivity of 31.0 g-dry biomass per m2-installation area per day to be achieved, which corresponded to a photosynthetic efficiency of 7.50% (photosynthetically active radiation (PAR; 400-700 nm)). This high photosynthetic performance was possible because smoother medium flow attained in single units was also attained in the four-unit system.     

The impact of the phytochromes on photosynthetic processes

This review describes the phytochrome system in higher plants and cyanobacteria and its role in regulation of photosynthetic processes and stress protection of the photosynthetic apparatus. A relationship between the content of the different phytochromes, the changes in the ratios of the physiologically active forms of phytochromes to their total pool and the resulting influence on photosynthetic processes is reviewed. The role of the phytochromes in the regulation of the expression of genes encoding key photosynthetic proteins, antioxidant enzymes and other components involved in stress signaling is elucidated.