杨梅光合作用的低温光抑制

利用便携式调制叶绿素荧光仪和光合作用测定系统研究了短期低温光照对杨梅幼树光合作用的影响。结果表明,低温光照处理后,杨梅叶片的Pn（净光合速率）、Gs（气孔导度）、Fv／Fm（最大的光系统Ⅱ光化学效率）、qP（光化学猝灭系数）和①PSⅡ（光系统Ⅱ的量子产量）下降,Ci／Ca（细胞间隙CO2浓度／环境CO2浓度）、Fo（初始荧光）、qN（非光化学猝灭系数）和（Fi—Fo）／（Fp—Fo）（失活的PSⅡ反应中心数量）上升。此外在同一水平低温下,中等强光（350μmol m^-2s^-1）加剧了PSⅡ反应中心的失活或破坏并且需要更长时间来恢复。这些结果说明低温和有光照条件下引起的杨梅光合作用下降是由于光合机构活性下降所致,即主要是PSⅡ反应中心的失活或破坏：我们推测QA^-（还原态质体醌A）和非还原QB（质体醌B）数量的积累可能是导致PSⅡ反应中心失活或破坏的原因,在低温光抑制过程中非辐射能量耗散对保护光合机构起着重要作用。     

水分胁迫下大丽花光合及叶绿素荧光的日变化特性

以大丽花品种‘粉西施’为试验材料,采用盆栽方法,研究了不同土壤含水量处理对‘粉西施’叶片光合及荧光特性日变化的影响。结果表明:随着水分胁迫程度的加深,大丽花叶片的Pn、Tr和Gs日平均值均降低,Ci日平均值在轻度和中度胁迫下降低,在重度胁迫下升高;在轻度和中度水分胁迫下大丽花Pn降低的主要原因是气孔限制,而重度水分胁迫下是非气孔因素;Pn在水分胁迫下的日变化曲线由单峰型变成双峰型,出现"午休"现象,且Tr和Gs在水分胁迫下的日变化曲线和Pn一致,但Ci日变化较平稳,与Pn相反。随着水分胁迫程度的加深,大丽花叶片的初始荧光(F0)日平均值升高,日变化曲线呈倒"V"型,PSⅡ反应中心可能破坏或可逆失活;Fm、Fv/Fm和ΦPSⅡ日平均值均降低,日变化曲线呈"V"型。水分胁迫使大丽花光抑制程度加深,抑制了PSⅡ的光化学活性,致使用于光化学反应的光能及实际光化学效率降低。研究结果发现,大丽花品种‘粉西施’在不同水分胁迫下都产生了光合作用的光抑制而使净光合速率降低;光合机构可适应轻度和中度水分胁迫而发生可逆失活,没有受到不可恢复的伤害,而重度水分胁迫降低了叶片的光合机构活性,加剧了光抑制程度,严重限制了光合作用;适宜大丽花生长的土壤含水量应为田间最大持水量的30%以上。     

低温胁迫对广玉兰幼苗光合及叶绿素荧光特性的影响

以广玉兰幼苗为材料,对其进行0,-4℃、-8℃,-12℃和-16℃ 5个梯度低温处理,研究了广玉兰幼苗的光合作用与叶绿素荧光特性变化.结果表明:随着温度降低,广玉兰幼苗叶片的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(G3)、叶肉细胞间隙CO2浓度(Ci)、叶绿素含量均逐步降低,最大光化学效率(Fv/Fm)、潜在光化学效率(Fv/F0)、最大量子产额(Yield)、光合电子传递速率(ETR)、光化学猝灭系数(qp)也均同时下降,而初始荧光(F0)、非光化学猝灭系数(qN)则逐步上升.可见,低温胁迫除导致光合作用的气孔抑制外,还直接损伤光合机构使PSⅡ反应中心失活,引起其光能原初捕捉能力和光能同化率减弱,增加了通过热辐射消耗的光能比例,最终导致广玉兰幼苗光合作用能力减弱.     

在盐胁迫下光抑制及其恢复进程对冬小科光合功能的影响

研究了盐和强光双重胁迫以及在弱光下恢复对冬小麦（Triticum aestivum L.）光合功能的影响。结果表明,单纯用低浓度盐（200mmol/L NaCl）胁迫时,对反向PSⅡ光合功能的Fv/Fo、Fv/Fm和qP等参数没有什么影响,但巳十分明显地抑制光合碳同化能力,而高盐（400mmol/L NaCl）胁迫损伤PSⅡ功能,从而加剧对碳同化功能的抑制,说明光合作用对不同盐浓度的响应不同。研究结果还表明,盐胁迫能加剧强光对光合功能的损伤,使之受到更加严重的光抑制。在低盐浓度下,光抑制初期形成形成QB-非还原性PSⅡ反应中心,在随后的光抑制进程和弱光下恢复期间,能有效的被用来合成有活性的PSⅡ和修复可逆性失活的PSⅡ反应中心。而高盐和强光双重胁迫使PSⅡ遭受严重破坏,QB-非还原性PSⅡ反应中心只有在光抑制初期可部分地用于修复可逆性失活的PSⅡ,随着光抑制的进程,它们不能用于合成有活性PSⅡ和修复受严重破坏的PSⅡ,结果导致它们的含量在弱光下恢复时继续增加。     

气温升高与干旱胁迫对宁夏枸杞光合作用的影响

以宁夏枸杞1年生苗木为材料,采用开顶式生长室模拟增温环境,设置两个温度水平(正常环境温度,增温=正常环境温度+2.5—3.7℃)和3个土壤水分水平(正常水分条件(田间最大持水量的70%—75%)、中度干旱处理(田间最大持水量的50%—55%)和重度干旱处理(田间最大持水量的35%—40%)),研究气温升高和干旱胁迫对宁夏枸杞光合作用的影响。结果表明:(1)在增温条件下,中度和重度干旱处理下的净光合速率比对照(正常供水)分别下降17.5%、48.9%,气孔导度平均下降了3.9%,水分利用效率仅为正常环境温度下的57.8%。(2)在气温升高和干旱胁迫交互作用下,枸杞叶片的净光合速率、气孔导度、胞间CO2浓度显著下降的同时,增温处理又加剧了枸杞植株的蒸腾耗水,从而导致枸杞叶片水分的利用效率和CO2同化能力降低。(3)气温升高和干旱胁迫交互作用降低了枸杞的PSⅡ活性中心的光能转换效率、使光合机构和PSⅡ反应中心受到损伤,从而导致枸杞光合作用效率下降。(4)气温升高加剧了干旱胁迫对宁夏枸杞叶片净光合速率和水分利用效率的减小作用,即气温升高加剧了干旱胁迫对宁夏枸杞光合作用的抑制作用。     

模拟酸雨对龙眼叶片PSⅡ反应中心和自由基代谢的影响

酸雨对植物光合机构的伤害机理一直是生态学研究的热点之一,为了探讨叶面酸化导致的PSⅡ反应中心损伤和光合机构自由基累积之间的内在联系,以1年生龙眼(Dimocarpus longana Lour.)实生小苗为研究对象,采用盆栽试验,研究了模拟酸雨胁迫对龙眼叶片叶绿素荧光参数和自由基代谢的影响.结果表明:酸雨胁迫改变了龙眼叶片的快速叶绿素荧光诱导动力学曲线形状,伤害PSⅡ反应中心;pH2.5酸雨胁迫5d后最大光化学效率(Fv/Fm)、PSⅡ反应中心活性(1/F0-1/FM)、反应中心含量(RC/CSo)急剧下降;有活性反应中心的关闭程度(VJ)、失活反应中心的比例(Non-QA和Non-QB)显著增加,QA迅速还原;放氧复合体(OEC)被破坏;PSⅡ受体侧电子传递体数(Sm)、电子转化效率(ψ0)和电子传递速率((φ)E0)明显降低,叶面酸化导致光系统线性电子传递受损.pH2.5酸雨胁迫5d后叶片超氧阴离子自由基(O2(-))、过氧化氢(H2O2)和丙二醛(MDA)含量显著增加;抗坏血酸(AsA)和谷胱甘肽(GSH)转化为氧化型,还原型减少;超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDAR)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性下降,叶绿体内自由基不能被及时清除,过多的自由基损伤光合器官,导致龙眼叶片PSⅡ受伤害.模拟酸雨胁迫伤害龙眼叶片PSⅡ反应中心供体侧和受体侧的电子传递体,造成同化力不足,清除自由基能力下降,导致叶绿体自由基累积,光合机构受到伤害.     

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。     

在盐胁迫下光抑制及其恢复进程对冬小麦光合功能的影响(英文)

研究了盐和强光双重胁迫以及在弱光下恢复对冬小麦 (TriticumaestivumL .)光合功能的影响。结果表明 ,单纯用低浓度盐 (2 0 0mmol/LNaCl)胁迫时 ,对反映PSⅡ光合功能的Fv/Fo、Fv/Fm和qP等参数没有什么影响 ,但已十分明显地抑制光合碳同化能力 ,而高盐 (4 0 0mmol/LNaCl)胁迫损伤PSⅡ功能 ,从而加剧对碳同化功能的抑制 ,说明光合作用对不同盐浓度的响应不同。研究结果还表明 ,盐胁迫能加剧强光对光合功能的损伤 ,使之受到更加严重的光抑制。在低盐浓度下 ,光抑制初期形成的QB_非还原性PSⅡ反应中心 ,在随后的光抑制进程和弱光下恢复期间 ,能有效的被用来合成有活性的PSⅡ和修复可逆性失活的PSⅡ反应中心。而高盐和强光双重胁迫使PSⅡ遭受严重破坏 ,QB_非还原性PSⅡ反应中心只有在光抑制初期可部分地用于修复可逆性失活的PSⅡ ,随着光抑制的进程 ,它们不能用于合成有活性PSⅡ和修复受严重破坏的PSⅡ ,结果导致它们的含量在弱光下恢复时继续增加     

等渗盐分与水分胁迫对三角叶滨藜和玉米光合作用的影响

以溶液培养的三角叶滨藜(Atriplex triangularis)和玉米(Zeamays)为材料,测定了等渗的盐分和水分胁迫对2种植物光合作用的短期影响。结果表明:等渗的水分和盐分胁迫均会造成三角叶滨藜和玉米净光合速率(Pn)的降低,而且随着胁迫程度的增强,水分胁迫引起Pn下降的幅度要明显高于等渗的盐分胁迫;在较低渗透胁迫强度下,2种胁迫导致光合速率下降的主要原因是气孔限制;但在环境溶液渗透势为-1.0MPa时,水分胁迫对光合作用的影响逐渐转化成非气孔限制,而盐胁迫仍然是气孔限制起主要作用;由此可见,等渗透势的水分胁迫对2种植物光合系统的影响要明显大于盐分胁迫。     

增强UV-B辐射对柚树苗生长和生理特性效应研究

增强的UV-B辐射明显降低柚树苗的株高,叶面积,比叶面积,增加叶片厚度和叶肉密度.柚树苗叶片叶绿素,可溶性蛋白含量和硝酸还原酶活性降低,可溶性糖含量上升.不同品种柚苗对UV-B辐射反应存在差异,酸柚抗性较强.经UV-B增强处理后,叶片Pn值下降,Rd先上升后恢复原有水平.Fv/Fm,ΦPSⅡ,qP均有不同程度的降低,而qN和KD升高,表明增强UV-B导致PSⅡ失活,PSⅡ原初光化学效率、开放PSⅡ中心数目和非环式电子传递效率下降.部分激发能通过非光化学荧光猝灭形式耗散.UV-B辐射使叶片膜脂过氧化产物MDA含量大幅度上升.SOD和APX活性在处理初期提高,随后下降,初步推测:增强UV-B辐射诱导膜脂过氧化作用,攻击光合作用中心靶点并导致PSⅡ失活,进而降低植物光合能力和物质代谢强度,最终导致柚树苗生长受到抑制.     

Effects of gamma-aminobutyric acid on the photosynthesis and chlorophyll fluorescence parameters of muskmelon seedlings under hypoxia stress

By the method of hydroponic culture, this paper studied the effects of exogenous gamma-aminobutyric acid (GABA) on the photosynthetic pigment contents, photosynthesis, and chlorophyll fluorescence parameters of muskmelon seedlings under hypoxia stress. Hypoxia stress induced a significant decrease of photosynthetic pigment contents, resulting in the decrease of photosynthesis. Applying GABA could significantly increase the photosynthetic pigment contents, net photosynthetic rate (P(n)), stomatal conductance (G(s)), intercellular CO2 concentration (C(i)), carboxylation efficiency (CE), maximal photochemical efficiency of PS II (F(v)/F(m)), photochemical quenching (q(P)), apparent photosynthetic electron transfer rate (ETR), and quantum yield of PS II electron transport (phi(PS II)), and decrease the stomatal limitation value (L(s)), minimal fluorescence (F(o)), and non-photochemical quenching (NPQ) under both hypoxic and normal conditions. The alleviation effect of GABA on photosynthetic characteristics was more obvious under hypoxia stress. However, simultaneously applying GABA and VGB could significantly decrease the alleviation effect of GABA under hypoxia stress.     

紫细菌光合机构及光合作用基因的表达调控

紫细菌是研究细菌光合作用的重要生物。介绍了紫细菌光合机构捕光色素蛋白复合体Ⅰ(light-harvesting I)、捕光色素蛋白复合体Ⅱ(light-harvesting II)和光化学反应中心(reaction center)的结构, 并探讨了其光合作用基因的转录调控机制, 重点阐述了PpsR/AppA系统对紫细菌光合作用基因的转录调控。     

紫细菌光合机构及光合作用基因的表达调控

紫细菌是研究细菌光合作用的重要生物.介绍了紫细菌光合机构捕光色素蛋白复合体Ⅰ(light-harvestingⅠ)、捕光色素蛋白复合体Ⅱ(1ight-harvesting Ⅱ)和光化学反应中心(reaction center)的结构,并探讨了其光合作用基因的转录调控机制,重点阐述了PpsR/AppA系统对紫细菌光合作用基因的转录调控.     

Effects of Photoinhibition and Its Recovery on Photosynthetic Functions of Winter Wheat Under Salt Stress

Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat ( Triticum aestivum L.) under salt stress were studied. The results showed that several parameters associated with PSⅡ functions, e.g. Fv/Fo 、 Fv/Fm and qP were not influenced by lower salt concentration (200 mmol/L NaCl) while CO2 assimilation rate decreased significantly. When exposed to higher salt concentration (400 mmol/L NaCl), PSⅡ functions were significantly inhibited which led to the decrease of carbon assimilation. These results suggest that different concentrations of salt stress affected photosynthesis by different modes. Salt stress made photosynthesis more sensitive to strong light and led to more serious photoinhibition. Under lower concentration of salt stress, the QB-non-reductive PSⅡ reaction centers formed at the beginning of photoinhibition could be effectively used to compose active PSⅡ reaction center (RC) and repair the reversible inactivated PSⅡ RC. Under higher concentration of salt stress, PSⅡ reaction centers were seriously damaged during photoinhibition, the QB-non-reductive PSⅡ RC could only be partly effective at the early time of photoinhibition, thus led to the accumulation of QB-non-reductive PSⅡ RC in the course of restoration under dim light.     

Inhibition of photosynthesis and energy dissipation induced by water and high light stresses in rice

Photoprotection mechanisms of rice plants were studied when its seedlings were subjected to the combined stress of water and high light. The imposition of water stress, induced by PEG 6000 which was applied to roots, resulted in substantial inhibition of stomatal conductance and net photosynthesis under all irradiance treatments. Under high light stress, the rapid decline of photosynthesis with the development of water stress was accompanied by decreases in the maximum velocity of RuBP carboxylation by Rubisco (V(cmax)), the capacity for ribulose-1,5-bisphosphate regeneration (J(max)), Rubisco and stromal FBPase activities, and the quantum efficiency of photosystem II, in the absence of any stomatal limitation of CO(2) supply. Water stress significantly reduced the energy flux via linear electron transport (J(PSII)), but increased light-dependent and DeltapH- and xanthophyll-mediated thermal dissipation (J(NPQ)). It is concluded that the drought-induced inhibition of photosynthesis under different irradiances in the rice was due to both diffusive and metabolic limitations. Metabolic limitation of photosynthesis may be related to the adverse effects of some metabolic processes and the oxidative damage to the chloroplast. Meanwhile, an enhanced thermal dissipation is an important process to minimize the adverse effects of drought and high irradiance when CO(2) assimilation is suppressed.     

Effects of drought on photosynthesis in Mediterranean plants grown under enhanced UV-B radiation

The effects of drought on the photosynthetic characteristics of three Mediterranean plants (olive, Olea europea L.; rosemary, Rosmarinus officinalis L.; lavender, Lavandula stoechas L.) exposed to elevated UV-B irradiation in a glasshouse were investigated over a period of weeks. Drought conditions were imposed on 2-year-old plants by withholding water. During the onset of water stress, analyses of the response of net carbon assimilation of leaves to their intercellular CO2 concentration were used to examine the potential limitations imposed by stomata, carboxylation velocity and capacity for regeneration of ribulose 1,5-bisphosphate on photosynthesis. Measurements of chlorophyll fluorescence were used to determine changes in the efficiency of light utilization for electron transport, the occurrence of photoinhibition of photosystem II photochemistry and the possibility of stomatal patchiness across leaves. The first stages of water stress produced decreases in the light-saturated rate of CO2 assimilation which were accompanied by decreases in the maximum carboxylation velocity and the capacity for regeneration of ribulose 1,5-bisphosphate in the absence of any significant photodamage to photosystem II. Leaves of rosemary and lavender were more sensitive than those of olive during the first stages of the drought treatment and also exhibited increases in stomatal limitation. With increasing water stress, significant decreases in the maximum quantum efficiency of photosystem II photochemistry occurred in lavender and rosemary, and stomatal limitation was increased in olive. No indication of any heterogeneity of photosynthesis was found in any leaves. Drought treatment significantly decreased leaf area in all species, an important factor in drought-induced decreases in photosynthetic productivity. Exposure of plants to elevated UV-B radiation (0.47 W m(-2)) prior to and during the drought treatment had no significant effects on the growth or photosynthetic activities of the plants. Consequently, it is predicted that increasing UV-B due to future stratospheric ozone depletion is unlikely to have any significant impact on the photosynthetic productivity of olive, lavender and rosemary in the field.     

不同干旱胁迫下欧李光合及叶绿素荧光参数的响应

采用人为控制土壤含水量的方法对欧李进行轻度和重度干旱的处理,测定叶片的气体交换和叶绿素荧光参数的日变化。结果表明,干旱胁迫下欧李叶片净光合速率、蒸腾速率、水分利用效率、气孔导度、PSII最大光化学效率、光化学量子效率显著下降,但胞间CO2浓度、非光化学猝灭系数以及叶黄素循脱环氧化状态（Z＋0.5A）/（V＋A＋Z）和Z含量升高。两干旱处理植株的影响程度存在差异。这表明在长时间干旱条件下,欧李叶片光合作用的降低受到气孔与非气孔因素的双重影响,叶黄素循环的启动增加了胁迫条件下的热耗散能力以保护光合机构免受干旱胁迫的进一步伤害。     

Responses of the photosynthetic electron transport system to excess light energy caused by water deficit in wild watermelon

In plants, drought stress coupled with high levels of illumination causes not only dehydration of tissues, but also oxidative damage resulting from excess absorbed light energy. In this study, we analyzed the regulation of electron transport under drought/high-light stress conditions in wild watermelon, a xerophyte that shows strong resistance to this type of stress. Under drought/high-light conditions that completely suppressed CO(2) fixation, the linear electron flow was diminished between photosystem (PS) II and PS I, there was no photoinhibitory damage to PS II and PS I and no decrease in the abundance of the two PSs. Proteome analyses revealed changes in the abundance of protein spots representing the Rieske-type iron-sulfur protein (ISP) and I and K subunits of NAD(P)H dehydrogenase in response to drought stress. Two-dimensional electrophoresis and immunoblot analyses revealed new ISP protein spots with more acidic isoelectric points in plants under drought stress. Our findings suggest that the modified ISPs depress the linear electron transport activity under stress conditions to protect PS I from photoinhibition. The qualitative changes in photosynthetic proteins may switch the photosynthetic electron transport from normal photosynthesis mode to stress-tolerance mode.     

Effects of Reddening of Cotton (Gossypium hirsutum L.) Leaves on Functional Activity of Photosynthetic Apparatus

Strong inhibition of rates of CO₂ assimilation and transpiration, stomatal conductance, and water use efficiency as well as photosystem 2 (PS2) photochemical activity were related to the severity of reddening. The inhibition of photosynthesis in red cotton leaves was due to both decreased photochemical activity and stomatal limitation. Lowered photosynthetic capacity could be one of the main factors of reduced yield in reddening cotton.