两种化感物质对茄子幼苗光合作用及叶绿素荧光参数的影响

采用基质栽培,研究不同浓度的2,6-二叔丁基苯酚及邻苯二甲酸二甲酯对茄子幼苗光合作用及叶绿素荧光参数的影响.结果表明,两种化感物质使茄子叶片叶绿素含量、光合速率（P_n）、气孔导度（G_s）下降,细胞间隙CO₂浓度（C_i）先降低后升高;使茄子叶片的初始荧光(F_o)增加,PSⅡ最大光化学效率(F_v/F_m)、光系统Ⅱ光合电子传递量子效率(Ф_PSⅡ)、光化学猝灭系数(q_P)、天线转化效率(F_v^' /F_m^′)降低.2,6-二叔丁基苯酚使茄子叶片非光化学猝灭系数(q_N)先升高后降低,邻苯二甲酸二甲酯使q_N低于对照,对茄子叶片光合机构造成了伤害.     

塔里木河下游地下水位对柽柳叶绿素荧光特性的影响

选取塔里木河下游3处地下水埋深6m的监测井位作为研究点,结合典型生态监测断面的地下水位监测数据,分析不同地下水埋深处柽柳的叶绿素荧光特性和光系统的光合活性.结果表明:随着地下水埋深加大和干旱胁迫加剧,柽柳叶片的实际光化学效率、电子传输速率和光化学猝灭等参数普遍下降;非光化学猝灭和调节性能量耗散量子产量等参数显著升高,而最大光量子产量总体处于相对适宜状态.干旱胁迫下柽柳的PSII光合活性随地下水埋深增大而下降,捕获光能的过剩程度加剧,发生光抑制的几率增大,其自身良好的抗旱性和自我调节机制,使光系统II尚未发生显著光损伤.     

高温下杂交稻培矮64S／E32与其亲本的光合和抗逆参数的比较

超级稻培矮64S／E32(F1)及其亲本(父本‘E32’和母本‘培矮64S’)的剑叶在不同温度(28、35、40℃ 和45℃)恒温水浴中保温1 h,随着处理温度的升高,F1除了较其亲本有更稳定的光合色素Chl外,还有明显 增加的Car／Chl,相对高的热稳蛋白含量,高而且稳定的总的抗氧化能力。F1在高温下也有较亲本高的光合 能力。高温下,线性电子传递过程比光化学过程对温度更敏感,F1有比亲本更敏感的调节机制,Pn下降比 ΦPSⅡ、Fv／Fm下降快说明光合限制步骤可能主要是位于光合碳同化而不是光化学和光合电子传递过程。     

铝胁迫对蓼科植物生长和光合、蒸腾特性的影响

采用水培试验,设置5种铝处理浓度,研究了铝对3种蓼科植物酸模叶蓼、杠板归和辣蓼叶片光合、蒸腾和叶绿素荧光参数的影响。结果表明,高铝处理(400μmol.L-1)显著抑制3种蓼科植物地上部和根系生长,并且导致3种蓼科植物叶片叶绿素含量、Chla/Chlb、净光合速率(Pn)、水分利用效率(WUE)、PSII光合电子传递量子效率(φPSII)和光化学猝灭系数(qP)显著下降。中低铝处理(25~100μmol.L-1)时,与对照相比,酸模叶蓼生物量显著增加,杠板归显著减少,辣蓼先增加后减少。其中,酸模叶蓼和辣蓼叶绿素含量、Chla/Chlb、Pn、蒸腾速率(Tr)、胞间CO2浓度(Ci)、PSII最大光化学效率(Fv/Fm)、qP均未发生显著变化,但辣蓼WUE、φPSII和非光化学猝灭系数(NPQ)显著下降,酸模叶蓼无显著变化;而杠板归除Ci、Fv/Fm外,其余叶片光合、蒸腾及叶绿素荧光参数均出现显著下降。上述结果表明,酸模叶蓼在中低铝处理条件下可通过保持较高的叶绿素含量、Chla/Chlb、WUE、Pn、PSII反应中心光化学反应效率以及提高非辐射能量耗散来增强其对铝的耐性。     

超级高产小麦旗叶荧光动力学研究

探明超级小麦品种的旗叶光合作用与荧光动力学特性,为超级小麦品种选育利用提供理论依据。以超级小麦临麦4号为试验材料,应用CI-301PS型便携式光合作用测定系统和FMS-2便携式荧光测定仪(英国Hansatech公司)在田间试验中测定旗叶光合作用与荧光动力学参数。结果表明,与普通高产对照品种皖麦52和烟农19相比,超级小麦临麦4号的光合作用参数光合速率、光饱和点和CO2饱和点、羧化效率高,光补偿点和CO2补偿点低;光合机构系统工作参数PSII实际的光化学效率(ΦPSII)、光化学猝灭系数(qP)、PSII反应中心的激发能捕获效率(Fv/Fm)、PSⅡ潜在活性Fv/Fo和电子传递速率(ETR)值高,非光化学猝灭系数(NPQ)值低。这表明超级小麦临麦4号的光合机构系统工作能力强和工作效率高,保证旗叶光合作用的高效运行,为子粒灌浆提供充足的能量和碳水化合物。     

Photosynthetic Properties of Photosystem II in Arabidopsis thaliana lpa1 Mutant

In a previous study, we characterized a high chlorophyll fluorescence lpa1 mutant of Arabidopsis thaliana, in which approximately 20% photosystem (PS) II protein is accumulated. In the present study, analysis of fluorescence decay kinetics and thermoluminescence profiles demonstrated that the electron transfer reaction on either the donor or acceptor side of PSII remained largely unaffected in the lpa1 mutant. In the mutant, maximal photochemical efficiency (Fv/Fm, where Fm is the maximum fluorescence yield and Fv is variable fluorescence) decreased with increasing light intensity and remained almost unchanged in wild-type plants under different light conditions. The Fv/Fm values also increased when mutant plants were transferred from standard growth light to low light conditions. Analysis of PSII protein accumulation further confirmed that the amount of PSII reaction center protein is correlated with changes in Fv/Fm in lpa1 plants. Thus, the assembled PSII in the mutant was functional and also showed increased photosensitivity compared with wild-type plants.(Author for correspondence. Tel: +86 (0)10 6283 6256; Fax: +86 (0)10 8259 9384; E-mail: zhanglixin@ibcas.ac.cn)     

Expressing an RbcS Antisense Gene in Transgenic Flaveria bidentis Leads to an Increased Quantum Requirement for CO2 Fixed in Photosystems I and II

It was previously shown with concurrent measurements of gas exchange and carbon isotope discrimination that the reduction of ribulose-1,5-bisphosphate carboxylase/oxygenase by an antisense gene construct in transgenic Flaveria bidentis (a C4 species) leads to reduced CO2 assimilation rates, increased bundle-sheath CO2 concentration, and leakiness (defined as the ratio of CO2 leakage to the rate of C4 acid decarboxylation; S. von Caemmerer, A. Millegate, G.D. Farquhar, R.T. Furbank [1997] Plant Physiol 113: 469-477). Increased leakiness in the transformants should result in an increased ATP requirement per mole of CO2 fixed and a change in the ATP-to-NADPH demand. To investigate this, we compared measurements of the quantum yield of photosystem I and II ([phi]PSI and [phi]PSII) with the quantum yield of CO2 fixation ([phi]CO2) in control and transgenic F. bidentis plants in various conditions. Both [phi]PSI/[phi]CO2 and [phi]PSII/[phi]CO2 increased with a decrease in ribulose-1,5-bisphosphate carboxylase/oxygenase content, confirming an increase in leakiness. In the wild type the ratio of [phi]PSI to [phi]PSII was constant at different irradiances but increased with irradiance in the transformants, suggesting that cyclic electron transport may be higher in the transformants. To evaluate the relative contribution of cyclic or linear electron transport to extra ATP generation, we developed a model that links leakiness, ATP/NADP requirements, and quantum yields. Despite some uncertainties in the light distribution between photosystem I and II, we conclude from the increase of [phi]PSII/[phi]CO2 in the transformants that cyclic electron transport is not solely responsible for ATP generation without NADPH production.     

Chill-induced inhibition of photosynthesis: genotypic variation within Cucumis sativus

Cucumber is generally a thermophilic species; however, cultivars have been selected for higher yield during winter cultivation in unheated glasshouses in temperate regions. We tested whether photosynthesis in these varieties had greater chilling tolerance. There was no difference in the instantaneous reduction of photosynthesis at low temperature between four winter glasshouse and four summer field cultivars. After 5 d of 10 degrees C and 100 micro mol m(-2) s(-1) photon flux density, the four field cultivars had a sustained depression of photosynthesis after returning to clement conditions. This inhibition was associated with reduced rates of CO(2) fixation and photosystem II (PSII) electron transport in the light, but not with sustained PSII photoinhibition. However, photosynthesis in the glasshouse genotypes was nearly identical to the pre-chill rates. Chill impacts on light-adapted chlorophyll fluorescence parameters, such as the quantum yield of PSII electron transport (phi(PSII)), correlated well with overall photosynthesis. This demonstrates the potential for using these fast and non-invasive techniques to screen for chill-tolerant genotypes, with the potential to further improve winter cucumber yield in unheated glasshouses.     

缺铁对大豆叶片光合作用和光系统Ⅱ功能的影响

通过气体交换和叶绿素荧光测定研究了缺铁对大豆叶片碳同化和光系统Ⅱ的影响。缺铁条件下大豆光合速率(Pn)大幅下降;最大光化学效率(po)下降幅度较小;荧光诱导动力学曲线发生明显的变化,其中电子传递活性明显下降,K相(VK)相对荧光产量提高。缺铁大豆的天线转化效率(Fv'/Fm')、光化学猝灭系数(qP)和光系统Ⅱ实际光化学效率(ΦPSⅡ)降低,而非光化学猝灭(NPQ)则明显增加。此外,缺铁大豆的光后荧光上升增强。据此,认为铁缺乏伤害了光系统Ⅱ复合物供体侧和受体侧的电子传递;缺铁条件下光系统I环式电子传递的增强可能在维持激发能耗散和ATP供给方面起一定作用。     

追施氮肥时期对冬小麦旗叶叶绿素荧光特性的影响

在大田条件下,研究了不同追氮时期对小麦旗叶叶绿素荧光特性、光合速率及籽粒产量的影响.结果表明,拔节期追肥较起身期或挑旗期追肥,改善了小麦旗叶PSⅡ的活性(F_v/F_o)、光化学最大效率(F_v/F_m)、光化学猝灭系数(qP)、实际量子产量(ΦPSⅡ)及光合速率,降低了籽粒灌浆中前期非辐射能量耗散,有利于叶片所吸收的光能较充分地用于光合作用,提高了籽粒灌浆后期非辐射能量的耗散,减缓了叶片光抑制程度和衰老进程.拔节期追肥可显著增加穗粒数和千粒重,提高产量.     

Temperature Dependence of the Linkage of Quantum Yield of Photosystem II to CO2 Fixation in C4 and C3 Plants

The temperature dependence of quantum yields of electron transport from photosystem II (PSII) ([phi]II, determined from chlorophyll a fluorescence) and CO2 assimilation ([phi]CO2, apparent quantum yield for CO2 assimilation) were determined simultaneously in vivo. With C4 species representing NADP-malic enzyme, NAD-malic enzyme, and phosphoenolpyruvate carboxykinase subgroups, the ratio of [phi]II/[phi]CO2 was constant over the temperature range from 15 to 40[deg]C at high light intensity (1100 [mu]mol quanta m-2 s-1). A similar response was obtained at low light intensity (300 [mu]mol quanta m-2 s-1), except the ratio of [phi]II/[phi]CO2 increased at high temperature. When the true quantum yield for CO2 fixation ([phi]CO2*) was calculated by correcting for respiration in the light (estimated from temperature dependence of dark respiration), the ratio of [phi]II/[phi]C02* remained constant with varying temperature and under both light intensities in all C4 species examined. Because the [phi]II/[phi]CO2* ratio was the same in C4 monocots representing the three subgroups, the ratio was not affected by differences in the bio-chemical mechanism of concentrating CO2 in the bundle sheath cells. The results suggest that PSII activity is closely linked to the true rate of CO2 fixation in C4 plants. The close relationship between [phi]II and [phi]CO2* in C4 species under varying temperature and light intensity conditions is apparently due to a common low level of photorespiration and a primary requirement for reductive power in the C3 pathway. In contrast, in a C3 plant the [phi] II/[phi]CO2* ratio is higher under normal atmospheric conditions than under nonphotorespiratory conditions and it increases with rising temperature. This decrease in efficiency in utilizing energy derived from PSII for CO2 fixation is due to an increase in photorespiration. In both the C3 and C4 species, photochemistry is limited under low temperature, and thus excess energy must be dissipated by nonphotochemical means.     

不同光强下高锰对黄瓜光合作用特性的影响

采用营养液培养的方法,研究了不同光强下高锰对黄瓜植株生长、叶绿素含量、叶绿素荧光参数和光合作用的影响.结果表明,高锰处理抑制了黄瓜植株的生长,与弱光处理相比强光下抑制幅度更加显著.强光下,高锰处理显著降低叶绿素含量,但降低光强却增加其含量.强光下,高锰处理显著降低原初光能转换效率(F_v/F_m)、光合电子传递量子效率(ΦPSII)和光化学猝灭系数(qP);弱光下,高锰处理对F_v/F_m和qP无显著影响.高锰处理使净光合速率(P_n)和气孔导度(G_s)下降.尤其是在强光下下降幅度更大.高锰处理使细胞间CO₂浓度(C_i)在强光下升高,而在弱光下则下降.与C_i相反,高锰处理使气孔限制值(L_s)在强光下下降,而在弱光下上升.因此,强光下高锰胁迫使净光合速率下降可能是由非气孔限制引起的,而弱光下高锰处理使净光合速率下降可能是由气孔因子限制引起的.     

不同氮素水平下二氧化碳加富对草莓叶片光抑制的影响

用便携式调制叶绿素荧光仪和光合仪研究了强光下不同供氮水平（12、4和0.4 mmol·L^-1）和不同CO₂浓度下（700和390 μl·L^-1）丰香草莓叶片的荧光参数及净光合速率的变化.结果表明,CO₂和氮素对草莓叶片光抑制有明显的互作效应.在富CO₂下,12 mmol·L^-1供氮水平的草莓叶片净光合速率升高了62.7%,4和0.4 mmol·L^-1供氮水平则分别降低了7.4%和21.3%;12 mmol·L^-1供氮水平的F_m和F_v/F_m在强光胁迫时降辐减小,暗恢复时F_m和F_v/F_m恢复程度提高,而4和0.4 mmol·L^-1供氮水平却相反.表明氮素供应不足时草莓叶片在富CO₂环境下光合作用出现适应性下调,光抑制增强.     

华山新麦草光合特性对干旱胁迫的响应

以濒危植物华山新麦草为材料进行盆栽试验,设置3个水分梯度,研究生长指标、气体交换、叶绿素荧光参数、光合色素含量、光响应特征及丙二醛(MDA)含量.结果表明:随干旱胁迫的加剧,株高、叶宽和光合色素含量降低,根长和丙二醛(MDA)含量增加;水分胁迫导致净光合速率(PN)、气孔导度(gs)、蒸腾速率(E)、最大荧光(Fm)、光合电子传递速率(ETR)和光化学猝灭系数(qP)降低,胞间CO2浓度(Ci)、瞬时水分利用效率(WUE)、初始荧光(Fo)和非光化学淬灭系数(NPQ)升高;光系统Ⅱ最大光化学效率(Fv/Fm)不变;干旱胁迫下光响应曲线拟合结果显示,干旱胁迫造成最大光合速率和光能利用效率下降.综上表明,干旱对光系统Ⅱ的伤害是制约华山新麦草光合作用的主要原因.     

Changes in photosystem II function during senescence of wheat leaves

Analyses of chlorophyll fluorescence were undertaken to investigate the alterations in photosystem II (PSII) function during senescence of wheat ( Triticum aestivum L. cv. Shannong 229) leaves. Senescence resulted in a decrease in the apparent quantum yield of photosynthesis and the maximal CO₂ assimilation capacity. Analyses of fluorescence quenching under steady‐state photosynthesis showed that senescence also resulted in a significant decrease in the efficiency of excitation energy capture by open PSII reaction centers (F'_v/F'_m) but only a slight decrease in the maximum efficiency of PSII photochemistry (F'_v/F'_m). At the same time, a significant increase in non‐photochemical quenching (q_N) and a considerable decrease in photochemical quenching (q_P) were observed in senescing leaves. Rapid fluorescence induction kinetics indicated a decrease in the rate of Q_A reduction and an increase in the proportion of Q_B‐non‐reducing PSII reaction during senescence. The decrease in both F'_v/F'_m and q_P explained the decrease in the actual quantum yield of PSII electron transport ((φ_PSII). We suggest that the modifications in PSII function, which led to the down‐regulation of photosynthetic electron transport, would be in concert with the lower demand for ATP and NADPH in the Calvin cycle which is often inhibited in senescing leaves.     

Modifications in photosystem II photochemistry in senescent leaves of maize plants

Analyses of CO2 exchange and chlorophyll fluorescence were carried out to assess photosynthetic performance during senescence of maize leaves. Senescent leaves displayed a significant decrease in CO2 assimilatory capacity accompanied by a decrease in stomatal conductance and an increase in intercellular CO2 concentration. The analyses of fluorescence quenching under steady-state photosynthesis showed that senescence resulted in an increase in non-photochemical quenching and a decrease in photo-chemical quenching. It also resulted in a decrease in the efficiency of excitation energy capture by open PSII reaction centres and the quantum yield of PSII electron transport, but had very little effect on the maximal efficiency of PSII photochemistry. The results determined from the fast fluorescence induction kinetics indicated an increase in the proportion of QB-non-reducing PSII reaction centres and a decrease in the rate of QA reduction in senescent leaves. Theoretical analyses of fluorescence parameters under steady-state photosynthesis suggest that the increase in the non-photochemical quenching was due to an increase in the rate constant to thermal dissipation of excitation energy by PSII and that the decrease in the quantum yield of PSII electron transport was associated with a decrease in the rate constant of PSII photochemistry. Based on these results, it is suggested that the decrease in the quantum yield of PSII electron transport in senescent leaves was down-regulated by an increase in the proportion of QB-non-reducing PSII reaction centres and in the non-photochemical quenching. The photosynthetic electron transport would thus match the decreased demand for ATP and NADPH in carbon assimilation which was inhibited significantly in senescent leaves.Key words: Chlorophyll fluorescence, gas exchange, maize (Zea mays L.), photochemical and non-photochemical quenching, photosystem II photochemistry.      

Loss of the precise control of photosynthesis and increased yield of non‐radiative dissipation of excitation energy after mild heat treatment of barley leaves

The after effects of a short exposure of intact barley leaves to moderately elevated temperature (40°C, 5 min) on the induction transients and the irradiance dependencies of photosynthesis and chlorophyll fluorescence are presented. This mild heat treatment strongly reduced the oscillations in the rate of photosynthesis and in the yield of chlorophyll fluorescence. However, only a 25% irreversible inhibition of maximum photosynthetic capacity of photosystem II (PSII) measured by oxygen evolution was produced and the intrinsic quantum yield of PSII measured by the chlorophyll fluorescence ratio (F_m‐ F_o)/F_m decreased by only 15%. In contrast, the above treatment increased radiationless dissipation processes in PSII by a factor of two. In heat‐treated leaves, photosynthesis was not saturated even by strong light. Both ΔpH‐dependent quenching of excitons in PSII (including formation of zeaxanthin) and state 1/state 2 transition were found to be stimulated. Heat exposure enhanced the control of PSII activity by PSI, as evidenced by a significant increase in the quenching effect of far‐red light on the maximum yield of chlorophyll fluorescence. It was deduced that after mild heat treatment, the photosynthetic apparatus in leaves lacks the precise coordinating control of electron transport and carbon metabolism owing to the inability of PSII to support electron transport at a level adequate for carbon metabolism. This effect was not related to the small irreversible thermal damage to PSII, but was rather due to a significant increase in non‐photochemical quenching of excitation energy.     

Relationship between photosystem II activity and CO2 fixation in leaves

There is now potential to estimate photosystem II (PSII) activity in vivo from chlorophyll fluorescence measurements and thus gauge PSII activity per CO₂ fixed. A measure of the quantum yield of photosystem II, Φ_II (electron/photon absorbed by PSII), can be obtained in leaves under steady-state conditions in the light using a modulated fluorescence system. The rate of electron transport from PSII equals Φ_II times incident light intensity times the fraction of incident light absorbed by PSII. In C₄ plants, there is a linear relationship between PSII activity and CO₂ fixation, since there are no other major sinks for electrons; thus measurements of quantum yield of PSII may be used to estimate rates of photosynthesis in C₄ species. In C₃ plants, both CO₂ fixation and photorespiration are major sinks for electrons from PSII (a minimum of 4 electrons are required per CO₂, or per O₂ reacting with RuBP). The rates of PSII activity associated with photosynthesis in C₃ plants, based on estimates of the rates of carboxylation (v_o) and oxygenation (v_o) at various levels of CO₂ and O₂, largely account for the PSII activity determined from fluorescence measurements. Thus, in C₃ plants, the partitioning of electron flow between photosynthesis and photorespiration can be evaluated from analysis of fluorescence and CO₂ fixation.     

模拟酸雨胁迫下硅对髯毛箬竹光合特性的影响

以髯毛箬竹为试验材料,研究了模拟酸雨胁迫(pH 3.0)下硅对髯毛箬竹叶片叶绿素相对含量、光合作用日变化以及叶绿素荧光特性等的影响.结果表明:20和100 mg·L^-1 Na₂SiO₃预处理可以不同程度地抑制酸雨胁迫下髯毛箬竹叶片叶绿素含量的显著下降,且以100 mg·L^-1浓度处理效果最佳,叶绿素含量可提高22.7%,而高浓度(500 mg·L^-1)预处理则无缓解作用-酸雨胁迫下,髯毛箬竹光合“午休”现象加重,日平均净光合速率(P_n)、气孔导度(G_s)和气孔限制值(L_s)明显降低,而胞间CO₂浓度(C_i)增大,经过20～100 mg·L^-1硅预处理后,P_n、G_s、L_s不同程度增加,而C_i有所降低,且以100 mg·L^-1硅预处理效果最佳,日平均P_n增加39.2%.酸雨胁迫下,箬竹PSⅡ最大荧光(F_m)、最大光化学效率(F_v/F_m)、潜在活性(F_v/F_o)、有效光化学效率(F_v′/F_m′)、最大荧光产额(F_m′)、光化学淬灭系数(q_P)、非光化学淬灭系数(q_N)、PSII实际光化学效率(Φ_PSⅡ)降低,暗适应和光适应下的最小荧光产额F_o、F_o′ 则升高;而100 mg·L^-1硅预处理明显抑制了胁迫下各荧光参数的变化,F_v/F_m、F_v/F_o、F_v′/F_m′和Φ_PSⅡ分别增加35.2%、146.2%、55.0%和24.3%.说明外源适宜浓度硅预处理能有效地缓解酸雨胁迫导致的髯毛箬竹光合活性下降和光合系统损伤,从而提高胁迫下植物的光合能力.     

Photosynthetic characterization of Jerusalem artichoke during leaf expansion

Gas exchange, chlorophyll a fluorescence and modulated 820 nm reflection were investigated to explore the development of photosynthesis in Jerusalem artichoke (Helianthus tuberosus L.) leaves from initiation to full expansion. During leaf expansion, photosynthetic rate (Pn) increased and reached the maximal level when leaves were fully expanded. The same change pattern was also found in the stomatal conductance and chlorophyll content. Lower Pn could not be ascribed to the higher stomatal resistance in developing leaves, as intercellular CO₂ concentration was not significantly lower in these leaves. Lower Pn partly resulted from the lower actual photochemical efficiency of PSII in developing leaves, as more excited energy was dissipated through non-photochemical quenching. The development of primary photochemical reaction and electron transport in the donor side of PSII was completed in the initiating leaves. However, the development of electron transport in the acceptor side of PSII was not accomplished until leaves were fully expanded, indicated by the change in probability that an electron moves further than primary quinone (ψo). PSI activity changed in parallel with ψo suggesting that PSI cooperated well with PSII during leaf expansion. It should be stressed that the development of carbon fixation process was later than primary photochemical reaction but earlier than photosynthetic electron transport during leaf expansion. The later development of photosynthetic electron transport may reduce the production of reactive oxygen species from Mehler reaction, particularly under low carbon fixation.