生长调节剂对黄连木光合生理指标和荧光参数的影响

以黄连木幼苗为试材,采用叶片喷施的方法,研究了生长调节剂多效唑和矮壮素对黄连木叶片解剖结构、色素含量、光合生理指标和叶绿素荧光参数的影响,以揭示生长调节剂对黄连木光合特性的影响及其内在机制。结果显示:随着两种生长调节剂处理浓度的增加,黄连木幼苗叶片厚度、栅栏组织厚度、海绵组织厚度、色素含量、净光合速率(Pn)、PSⅡ原初光能转化效率(Fv/Fm)、PSⅡ的潜在活性(Fv/F0)、叶片单位面积吸收的能量(ABS/CS)和捕获的能量(TRo/CS)以及电子传递的能量(ETo/CS)均呈先增大后减小的趋势,并均在800mg/L多效唑和500mg/L矮壮素处理时达到最大值,且显著提高了黄连木叶片的净光合速率。研究发现,黄连木幼苗叶片栅/海比例增大和叶绿素含量的增加使叶片对光能的捕获和吸收能力提高,而PSⅡ反应中心开放比例的增大与其活性的增强保证了叶片对光能的高效传递,同时降低了能量的热耗散,是提高苗木光合速率和保证苗木光合作用高效进行的内在机制。     

Growth parameters and photosynthetic pigments in leaf segments of Zea mays exposed to cadmium, as related to protection mechanisms

The influence of cadmium on growth parameters and photosynthetic pigment content was studied in maize leaf segments differing in tissue maturity. Experiments were carried out with maize seedlings Zea mays L. cv. Hidosil treated with 25, 50, 100, 150 and 200 microM Cd for 14 days under low light conditions. Tissue age-dependent decrease of fresh mass, dry mass and area of the leaf segments was correlated with Cd concentration in the growth medium. Cd induced changes in chlorophyll and carotenoid contents, and the specific areas and densities of the leaf segments were dependent on age and metal concentration. Results are discussed with respect to the protection mechanisms in the leaf segments.     

Modulation of Exogenous Glutathione in Phytochelatins and Photosynthetic Performance Against Cd Stress in the Two Rice Genotypes Differing in Cd Tolerance

Greenhouse hydroponic experiments were conducted using Cd-sensitive (Xiushui63) and tolerant (Bing97252) rice genotypes to evaluate genotypic differences in response of photosynthesis and phytochelatins to Cd toxicity in the presence of exogenous glutathione (GSH). Plant height, chlorophyll content, net photosynthetic rate (Pn), and biomass decreased in 5 and 50 μM Cd treatments, and Cd-sensitive genotype showed more severe reduction than the tolerant one. Cadmium stress caused decrease in maximal photochemical efficiency of PSII (Fv/Fm) and effective PSII quantum yield [Y(II)] and increase in quantum yield of regulated energy dissipation [Y(NPQ)], with changes in Cd-sensitive genotype being more evident. Cadmium-induced phytochelatins (PCs), GSH, and cysteine accumulation was observed in roots of both genotypes, with markedly higher level in PCs and GSH on day 5 in Bing97252 compared with that measured in Xiushui63. Exogenous GSH significantly alleviated growth inhibition in Xiushui63 under 5 μM Cd and in both genotypes in 50 μM Cd. External GSH significantly increased chlorophyll content, Pn, Fv/Fm, and Y(II) of plants exposed to Cd, but decreased Y(NPQ) and the coefficient of non-photochemical quenching (qN). GSH addition significantly increased root GSH content in plants under Cd exposure (except day 5 of 50 μM Cd) and induced up-regulation in PCs of 5 μM-Cd-treated Bing97252 throughout the 15-day and Xiushui63 of 5-day exposure. The results suggest that genotypic difference in the tolerance to Cd stress was positively linked to the capacity in elevation of GSH and PCs, and that alleviation of Cd toxicity by GSH is related to significant improvement in chlorophyll content, photosynthetic performance, and root GSH levels.     

Photosynthetic electron transport is differentially affected during early stages of cultivar/race-specific interactions between potato andPhytophthora infestans

The influence of the early stages of fungal infection on chloroplast metabolism was studied in cultivar/race-specific interactions between potato (Solanum tuberosum L. cv. Datura) and the late-blight fungusPhytophthora infestans. The accumulation of several mRNAs encoding components of the photosynthetic apparatus was not affected, either in compatible or in incompatible interactions. However, within 3 h after inoculation of potato leaves with fungal spores, a change in the photochemistry of photosystem II was detectable by measuring chlorophylla fluorescence. Characteristic fluorescence parameters, such as maximum fluorescence yield (F_m), variable fluorescence yield (F_v) and photochemical efficiency (F_v/F_m), were specifically reduced in the compatible host/pathogen interaction. Analyses of photochemical and nonphotochemical fluorescence quenching showed an increase in the photochemical fraction. The amounts of two selected thylakoid membrane proteins and of total chlorophyll remained unchanged during this process, suggesting that the functional modification of the electron-transport system was not correlated with a change in the composition of the photosynthetic apparatus. The alterations of photosynthetic electron transport represent a rapidly detectable and sensitive physiological marker for compatible interactions in the potato/Phytophthora infestans pathosystem.     

早熟桃夏季叶色转红过程中的光化学响应特征

比较研究了‘早美’和‘春蕾’2个早熟桃品种夏季叶色转红对太阳光能的利用和光系统Ⅱ的叶绿素荧光特征的影响。结果表明：早熟桃叶片色素组成的变化会显著影响其光合和叶绿素荧光特性。叶色转红后,早熟桃净光合速率（Pn）日均值、PSII最大光化学效率（Fv/Fm）、PSII实际光化学效率（ФPSII）均上升,无显著光抑制,而绿叶对照‘红花碧桃’的电子传递速率（ETR）、Fv／Fm和ФPSII值均显著下降,7月光合明显受抑制。叶色转红程度较深的‘早美’在夏季高温强光下表现优于‘春蕾’和对照。淬灭分析表明：叶片花色素苷的积累能在短时间内增加PSII天线色素吸收的光能用于光化学反应的份额（P）与用于反应中心热耗散的相对份额（D）。转红后的叶片光化学淬灭系数（qp）显著高于绿叶,PSII光化学效率较高,但耗散过剩激发能的能力显著低于绿叶对照。     

高温对仁用杏光合特性及PSⅡ光化学活性的影响

为探讨高温胁迫下仁用杏叶片的光合适应机制,以科尔沁沙地生长的4年生'超仁'仁用杏为试材,设置环境温度为25℃、30℃、40℃和50℃处理,利用气体交换技术和快速叶绿素荧光诱导动力学曲线分析技术(JIP-test),研究了仁用杏叶片光合特性和PSⅡ光化学活性.结果表明:在一定温度范围内,随着温度升高,仁用杏通过提高光合色素含量和比例来维持光能的吸收、传递和转换能力,从而保证光合机构正常运转;当高温超过叶片自身生理调节限度后,叶绿素发生分解、净光合速率(Pn)明显下降、胞间CO2浓度(Ci)上升,说明光合作用的下降是由叶肉因素造成的.温度40℃导致单位面积有活性反应中心数量(RC/CSo)显著下降;而50℃高温下荧光诱导曲线中K点(Wk)和J点(Vj)明显增加,高温对仁用杏叶片放氧复合体(OEC)、受体侧和PsⅡ反应中心造成了伤害.此外,50℃高温还导致初始荧光(Fo)显著升高,为对照的2.26倍,PSⅡ最大光化学效率(Fv/Fm)和光化学性能指数(PI/ABS)分别下降为对照的37.9%和10.3%.高温损害了PSⅡ供体侧和受体侧的功能,造成光合效率下降,这是高温胁迫对仁用杏叶片光合机构伤害的主要机制之一.     

外源NO对NaHCO3胁迫下黑麦草幼苗光合生理响应的调节

采用营养液砂培方法,研究了外源一氧化氮(NO)对100 mmol/L NaHCO3胁迫下黑麦草幼苗叶片叶绿素含量、光合气体交换和叶绿素荧光参数、光能分配及叶黄素循环的影响。结果表明:(1)外施60μmol/L NO供体硝普钠(SNP)显著缓解了NaHCO3胁迫下叶绿素含量、净光合速率(Pn)、气孔导度(Gs)和气孔限制值(Ls)的下降及胞间CO2浓度(Ci)的升高,提高了光系统Ⅱ(PSⅡ)的潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)和光化学猝灭(qP),降低了初始荧光(Fo)和非光化学猝灭(NPQ)。(2)NaHCO3胁迫下,外施SNP显著抑制了天线转换效率(Fv’/Fm’)的下降,降低了光系统间激发能分配的不平衡性(β/α-1)和天线热耗散的比例(D),提高了吸收光能中用于光化学反应的比例(P),而对PSⅡ反应中心的过剩光能(Ex)无明显影响。(3)外施SNP显著降低了NaHCO3胁迫下叶黄素循环库(V+A+Z)下降和叶黄素循环脱环氧化状态(A+Z)/(V+A+Z)上升的幅度。但SNP对NaHCO3胁迫的缓解效应可被NO清除剂血红蛋白(Hb)部分或完全地逆转,SNP的分解产物NaNO2处理对NaHCO3胁迫无明显改善。表明外源NO可能通过提高光化学效率,缓解了碱胁迫引起的光抑制对光合机构的破坏,从而提高黑麦草的光合效率。     

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.     

施氮和大气CO2浓度升高对小麦旗叶光合电子传递和分配的影响

采用开顶式气室盆栽培养小麦,设计2个大气CO2浓度(正常:400 μmol.mol-1;高:760 μmol·mol-1)、2个氮素水平(0和200 mg·kg-1土)的组合处理,通过测定小麦抽穗期旗叶氮素和叶绿素浓度、光合速率(Pn)-胞间CO2浓度(C1)响应曲线及荧光动力学参数,来测算小麦叶片光合电子传递速率等,研究了高大气CO2浓度下施氮对小麦旗叶光合能量分配的影响.结果表明:与正常大气CO2浓度相比,高大气CO2浓度下小麦叶片氮浓度和叶绿素浓度降低,高氮处理的小麦叶片叶绿素a/b升高.施氮后小麦叶片PSⅡ最大光化学效率(Fv/Fm)、PSⅡ反应中心最大量子产额(Fv'/Fm')、PSⅡ反应中心的开放比例(qr)和PSⅡ反应中心实际光化学效率(φPSⅡ)在大气CO2浓度升高后无明显变化,虽然叶片非光化学猝灭系数(NPQ)显著降低,但PSⅡ总电子传递速率(JF)无明显增加;不施氮处理的Fv'/Fm'、φPSⅡ和NPQ在高大气CO2浓度下显著降低,尽管Fv/Fm和qp无明显变化,JF仍显著下降.施氮后小麦叶片JF增加,参与光化学反应的非环式电子流传递速率(Jc)明显升高.大气CO2浓度升高使参与光呼吸的非环式电子流传递速率(J0)、Rubisco氧化速率(V0)、光合电子的光呼吸/光化学传递速率比(J0/Jc)和Rubisco氧化/羧化比(V0/Vc)降低,但使Jc和Rubisco羧化速率(Vc)增加.因此,高大气CO2浓度下小麦叶片氮浓度和叶绿素浓度降低,而增施氮素使通过PSⅡ反应中心的电子流速率显著增加,促进了光合电子流向光化学方向的传递,使更多的电子进入Rubisco羧化过程,Pn显著升高.     

Glycine betaine accumulation,ionic and water relations of red-beet at contrasting levels of sodium supply

Exposure of plants to sodium (Na) and salinity may increase glycine betaine accumulation in tissues. To study this, red-beet cvs. Scarlet Supreme and Ruby Queen, were grown for 42 days in a growth chamber using a re-circulating nutrient film technique with 0.25 mmol/L K and either 4.75 mmol/L (control) or 54.75 mmol/L (saline) Na (as NaCl). Plants were harvested at weekly intervals and measurements were taken on leaf water relations, leaf photosynthetic rates, chlorophyll fluorescence, chlorophyll levels, glycine betaine levels, and tissue elemental composition. Glycine betaine accumulation increased under salinity and this accumulation correlated with higher tissue levels of Na in both cultivars. Na accounted for 80 to 90% of the total cation uptake under the saline treatment. At final harvest (42 days), K concentrations in laminae ranged from approximately 65-95 micromoles g-1 dry matter (DM), whereas Na in shoot tissue ranged from approximately 3000-4000 micromoles g-1. Leaf sap osmotic potential at full turgor [psi(s100)] increased as lamina Na content increased. Glycine betaine levels of leaf laminae showed a linear relationship with leaf sap [psi(s100)]. Chlorophyll levels, leaf photosynthetic rates, and chlorophyll fluorescence were not affected by Na levels. These results suggest that the metabolic tolerance to high levels of tissue Na in red-beet could be due to its ability to synthesize and regulate glycine betaine production, and to control partitioning of Na and glycine betaine between the vacuole and the cytoplasm.     

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。     

不同供镁水平对两菊芋品种幼苗生物量、光合和叶绿素荧光特性的影响

采用砂培方式研究了不同供镁水平对"南芋1号(Nanyu No.1)"和"青芋2号(Qingyu No.2)"幼苗生物量、光合特性和叶绿素荧光特性的影响。结果表明:缺镁使菊芋叶片叶绿素含量显著降低,干物质积累减少,净光合速率、蒸腾速率和光合电子传递速率显著下降、CO2同化受抑制,同时Fv/Fm、ΦPSII、qP和qN也显著下降,加重了叶片受到光抑制的程度;随着供镁水平的增加,菊芋的干物质积累,叶绿素含量,光合参数和各系列荧光参数均呈现先增加后降低的趋势;南芋1号和青芋2号在镁离子浓度分别为3和6mmol.L-1,叶片的净光合速率、Fo、Fm、Fo’、Fm’、Fv/Fm、ΦPSII、ETR达到最高值,叶绿素a、b及总叶绿素含量也最多,干物质积累量最大;南芋1号的各系列荧光参数、光合参数、叶绿素含量和干物质积累量均显著高于青芋2号。     

水分胁迫与复水对地枫皮生理生态特性的影响

以岩溶特有药用植物地枫皮为材料,研究土壤水分胁迫及复水条件下,其叶片光合参数、叶绿素荧光参数及光合色素含量的变化特性,进而探讨其对水分胁迫的生理生态适应性。结果表明:停止供水10 d,水分胁迫地枫皮叶片的P_n(净光合速率)、C_i(胞间CO_2浓度)、G_s(气孔导度)和L_s(气孔限制值)均下降,气孔限制是P_n降低的主要原因;停止供水15 d,水分胁迫地枫皮叶片的P_n日变化呈逐渐下降趋势,上午9:30以后全天的P_n值均接近零,非气孔限制成为P_n下降的主要因素;而对照地枫皮叶片的P_n日变化呈"双峰型",中午P_n下降的主要原因依然是气孔限制。水分胁迫下,地枫皮叶片叶绿素含量降低和Chl_(a/b)升高,减少了叶片对光能的捕获,减轻了光合机构遭受光氧化的破坏,而Car/Chl_(a+b)升高增强了光保护能力。水分胁迫下,地枫皮叶片的初始荧光(F_o)显著增大,最大荧光(F_m)、光系统Ⅱ(PSⅡ)潜在活性(F_v/F_o)和最大光化学效率(F_v/F_m)均显著降低,表明水分胁迫对地枫皮叶片的PSⅡ反应中心和电子传递造成了一定的破坏,从而使其PSⅡ的潜在活性和最大光化学效率降低。复水5 d后,地枫皮的上述生理生态参数均能恢复到对照水平,表明其复水后的生理修复能力很强。     

镉胁迫对不同甘蓝基因型光合特性和养分吸收的影响

以2个耐镉(Cd)性不同的甘蓝品种为材料,研究了不同Cd浓度(0、20、50、100μmol.L-1)对甘蓝植株生长、叶片光合特性和养分吸收的影响.结果表明:Cd敏感品种在低浓度Cd(20μmol.L-1)处理下生长受到明显抑制,叶片净光合速率(Pn)、气孔导度(Gs)、PSⅡ光化学效率(Fv/Fm)、PSⅡ光合电子传递量子效率(ΦPSⅡ)及地上部、根系干质量显著降低;Cd耐性品种在高浓度Cd(50和100μmol.L-1)处理下生长和光合特性受到显著影响;Cd胁迫降低了甘蓝叶片叶绿素a和b含量,尤其对叶绿素a的影响较大,进而抑制了叶片光合能力.Cd胁迫显著降低了植株对Mn的吸收,抑制了Mg和Fe从根部向地上部的转运,且Cd敏感品种受抑制幅度更大;Cd胁迫促进了Cd耐性品种对P和S的吸收,而Cd敏感品种相反.因此,Cd胁迫下甘蓝敏感品种叶片Mn、Fe、Mg、S和P含量的降低是影响其叶片光合作用,进而抑制植株生长的重要生理原因.     

Oxalate Accumulation as Regulated by Nitrogen Forms and Its Relationship to Photosynthesis in Rice （Oryza sativa L.）

Four-leaf rice seedlings (Oryza sativa L.), which had been cultivated in Kimura B complete nutrient solution, were treated with two nitrogen forms by replacing the nitrogen element in the complete solution with sole nitrate or ammonium (2.86 mmol/L). Nitrate-N nutrition tended to increase oxalate content in all parts of the plant, including the leaves, stems, roots, and root exudates, whereas ammonium had the opposite effect. Consequently, marked differences in oxalate content were observed between the two treatments throughout the time tested (0-12 d), with maximal differences of approximately 12-fold at 6d after treatment. Photosynthetic/respiratory parameters were examined over time simultaneously with changes in oxalate content. Net photosynthetic rate, chlorophyll fluorescence parameters (i.e. maximal photochemical efficiency (Fv/Fm) and photochemical quantum yields of photosystem (PS)II (ΦPSⅡ)), and respiratory rate were not significantly different between plants treated with the two nitrogen forms, although ammonium-fed plants had apparently higher leaf chlorophyll content than nitrate-fed plants. Leaf glucose content was altered little, but the content of fructose, sucrose, and total soluble sugar was significantly higher in the leaves of ammonium-fed plants than nitrate-fed plants. The results indicate that nitrate/ammonium may serve as efficient regulators of oxalate accumulation owing to regulation of metabolism in rice leaves rather than oxalate downward transfer and root excretion, and that photosynthetic metabolism is not directly correlated with the regulation of oxalate accumulation in rice plants.     

不同性别桑树幼苗对镉与酸雨复合处理的生长响应及镉积累差异

为研究不同性别桑树在镉(Cd)与酸雨(AR)复合处理条件下的生长与镉积累差异,本试验以‘强桑1号’(雌株)和‘农桑14号’(雄株)两种不同性别桑树为材料,研究重金属镉(100 mg·kg^-1干土)和模拟酸雨(pH 3.0)处理下,两者生物量积累和分配、最大净光合速率(A_max)和叶绿素荧光参数,以及Cd积累与分配的差异.试验共设置无Cd和AR(对照)、单独Cd、单独AR、Cd+AR复合4个处理.结果表明:单独Cd处理虽然显著增加了雌株和雄株根茎叶中Cd含量,而且雌株各部分Cd含量显著高于雄株,但是只有雄株根、茎和总生物量、最大净光合速率显著下降,而雌株除了A_max显著下降外,各部分生物量积累下降均不显著,且两者的最大光化学效率(F_v/F_m)、光化学淬灭系数(q_P)和非光化学淬灭系数(q_N)均未发生显著变化.复合处理下,雄株和雌株的总生物量、A_max均显著降低,与单独镉处理相比,雌株根和叶中的Cd含量显著升高,但雄株没有明显变化,两者的F_v/F_m、q_P没有显著变化,但q_N均显著降低.短时间处理下桑树雌株对单独镉胁迫的耐受性高于雄株,但是酸雨的加入会降低雌株对镉的耐受性,可能是因为酸雨促进雌株根系对镉的吸收,并导致叶片积累了更多的镉.     

Photosynthesis in the basal growing zone of barley leaves

Cell proliferation, elongation, determination and differentiation mainly take place in the basal 5 mm of a barley leaf, the so-called basiplast. A considerable portion of cDNAs randomly selected from a basiplast cDNA library represented photosynthetic genes such as CP29, RUBISCO-SSU and type I-LHCP II. Therefore, we became interested in the role of the basiplast in establishing photosynthesis. (1) Northern blot analysis revealed expression of photosynthetic genes in the basiplast, although at a low level. Analysis of basiplasts at different developmental stages of the leaves revealed maximal expression of photosynthetic genes during early leaf development. The activity of these genes shows that plastid differentiation involves the development of the photosynthetic apparatus even at this early state of leaf cell expansion. (2) This conclusion was supported by the fact that chlorophylls and carotenoids are synthesized in the basiplast. The qualitative pattern of pigment composition was largely similar to that of fully differentiated green leaves. (3) The transition from proplastids to chloroplasts progressed in the basal 5 mm of the leaf, so that the number of grana lamellae per thylakoid stack increased with distance from the meristem from zero to about five. (4) Photosynthetic function was studied by chlorophyll a-fluorescence measurements. In dark-adapted 8-day-old primary leaves, the fluorescence ratio (F_P-F_o)/F_P was little decreased in basiplasts as compared to leaf blades. During steady state photosynthesis, the ratio (F_M-F_o)/F_M was high in leaf blade (0.5), but low in the sheath (0.25) and in the basiplast (0.18), indicating the existence of functional, albeit low light-adapted chloroplasts in the basiplast. (5) Further on, chlorophyll a fluorescence analysis in relation to seedling age revealed efficient photosynthetic performance in the basiplast of 3- to 6-day-old seedlings which later-on differentiates into leaf blade as compared to the basiplast of 7- to 12-day-old seedlings which develops into leaf sheath and finally ceases to grow. The leaf age dependent changes in basiplast photosynthesis were reflected by changes in pigment contents and LHCP II expression both of which also revealed a maximum in the basiplast of 4-day-old seedlings.Abbreviations bas 1 basiplast-associated gene 1 encoding a peroxide reductase - cab chlorophyll a/b binding protein - CP 29 29 kDa chlorophyll binding protein - DIG digoxigenin - EMIP epidermal major intrinsic protein - LHCP II light harvesting complex of Photosystem II - LSU large subunit of Rubisco - NPQ non photochemical chlorophyll a fluorescence quenching - PSI/PS II Photosystem I/II - PQ photochemical chlorophyll a fluorescence quenching - Rubisco Ribulose-1,5-bisphosphate carboxylase - SSU small subunit of Rubisco     

A Fragrant Solution to Soil Remediation

The ability of scented geraniums (Pelargonium sp. ‘Frensham’) plants to tolerate, uptake, and accumulate lead was assessed compared with two well-established metal accumulators, Indian mustard (Brassica juncea) and sunflower (Helianthus annuus), under greenhouse conditions. The efficiency of the photosynthetic apparatus and the number and size of active photosynthetic reaction centers (expressed as chlorophyll a fluorescence ratios of variable fluorescence to maximal fluorescence [Fv/Fm] and variable fluorescence to unquenchable portion of fluorescence [Fv/Fo], respectively) were affected to varying degrees at all metal concentrations in all the plants tested. Lead exposure did not significantly affect the efficiency of photosystem II activity or the number and size of the photosynthetic reaction centers in scented geraniums, but the ratios decreased significantly in Indian mustard and sunflower plants following lead exposure. In addition to tolerating high levels of lead, the scented geraniums accumulated in excess of 3000 mg of lead per kg DW of shoot and above 60,000 mg of lead per kg DW of root tissue. Additionally, scented geraniums exposed to a mixture of metals (lead + cadmium + nickel) had the ability to uptake in excess of 4.72% Pb + 0.44% Cd + 0.52% Ni per kg of root DW, as well as 0.17% Pb + 0.07% Cd + 0.14% Ni per kg of shoot DW within 14 d, indicated the potential for existence of more than one functional tolerance and metal uptake mechanism(s). The cellular localization of lead was assessed using transmission electron microscopy coupled with an X-ray microanalyzer. Lead accumulation was observed in the apoplasm and in the cytoplasm, vacuoles, and as distinct globules (potentially as lead-lignin or lead-phosphate complexes) on the cell membrane and cell wall. We conclude that the ability of scented geraniums to tolerate high lead accumulation in its biomass is due, in part, to limiting damage to photosynthetic apparatus and metal detoxification by formation of metal complexes.     

施氮和供水对混播和单播白羊草叶片叶绿素荧光特性的影响

为明确干旱条件下混播和施氮对白羊草〔Bothriochloa ischaemum(Linn.)Keng〕叶片叶绿素荧光参数的影响,采用盆栽法并设置不同混播比例〔白羊草与柳枝稷(Panicum virgatum Linn.)混播比例分别为8:0、6:2、4:4和2:6〕、施氮水平(即不施氮和1kg干土施01g纯氮)和供水条件(即正常供水和干旱胁迫6d后复水),对白羊草叶片叶绿素荧光参数的变化进行比较分析;在此基础上,采用一般线性模型分析这3个因素及其交互作用对白羊草叶绿素荧光参数的影响效应.结果显示:正常供水条件下,各处理组白羊草的最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)、表观光合电子传递速率(ETR)、光化学淬灭系数(qP)和非光化学淬灭系数(NPQ)均无明显变化.干旱及复水条件下,不施氮处理组白羊草的Fv/Fm值在干旱胁迫6 d(即土壤相对含水量最低)时降至最低值,并在复水2 d后恢复至与正常供水条件下相近的水平,而施氮处理组的Fv/Fm值则一直保持与正常供水条件下相近的水平;不论施氮与否,各处理组白羊草的ΦPSⅡ、ETR、qP和NPQ值基本上均表现为在干旱胁迫6 d时达到最高值,并在复水2 d后恢复至正常供水条件下各参数值的90%以上.总体上看,混播白羊草的qP和ETR值均高于单播白羊草,而其NPQ值则低于后者.统计分析结果表明:混播比例、施氮水平和供水条件3个因素间的交互作用对白羊草的ΦPSⅡ、qP和ETR值无显著影响,施氮水平对NPQ值的单独作用、施氮水平和混播比例的交互作用对Fv/Fm值以及施氮水平和供水条件的交互作用对ETR值也无显著影响,但这3个因素的单独作用及两两因素间的交互作用对白羊草其余叶绿素荧光参数均有显著或极显著影响.研究结果表明:一定程度的干旱胁迫有利于提高白羊草叶片PSⅡ反应中心的开放程度、光合电子传递速率和热耗散过剩光能的能力;在干旱胁迫条件下,施氮有助于白羊草叶片维持PSⅡ反应中心的活性和光化学效率;并且,与柳枝稷适度混播可改善白羊草叶片的光合性能,提高其种间竞争适应性.     

长期施氮对旱地小麦灌浆期叶绿素荧光参数的影响

探讨了长期施氮对黄土旱塬冬小麦灌浆期叶绿紊荧光的影响．结果表明,PSⅡ反应中心的实际光化学效率(φPSⅡ)随叶片水分胁迫的加剧而降低,施氮可明显提高φPsⅡ．施氮量为0kg·hm^-2、90kg·hm^-2和180kg·hm^-2三个处理中午时叶片的φPSⅡ分别为0．197、0．279和0．283,与上午相比分别降低了57．7％、56．4％和40．2％;下午各处理的φPSⅡ均得以恢复,0kg·hm^-2和90kg·hm^-2处理分别恢复到上午的87．3％和81．5％,180kg·hm^-2处理则完全恢复,并稍高于上午．施氮可提高PSⅡ的最大光化学量子效率(Fv／Fm)、光化学猝灭系数(qP)和非光化学猝灭系数(qNP)等荧光参数,表明施氮一方面提高了光能转换效率和PSⅡ的潜在活性,另一方面增强了过剩光能的非光化学耗散,有利于保护光合机构免受环境胁迫的破坏．但90kg·hm^-2和180kg·hm^-2施氮处理之间对光合的促进作用差异不显著,表明过量施氮无助于光合性能的提高,作物的光合能力并不随施氮量而同比例的改善。