利用叶绿素荧光评估草原植物羊草缺磷缺氮状况北大核心CSCD

羊草(Leymus chinensis)是北方草原的重要牧草。准确评估其营养状况,对维护羊草草原的生产力具有重要意义。以羊草幼苗为材料,利用能同时表征2个光系统光化学活性的叶绿素荧光检测技术,对缺氮和缺磷处理下的叶片光化学活性进行分析。结果表明,缺氮处理20天后羊草叶片叶绿素含量降低近50%。同期缺磷及缺氮处理对PSⅡ功能的影响总体大于PSⅠ。与对照相比,缺氮叶片的Φ(Ⅱ)和Φ(Ⅰ)分别比对照降低了30.3%与38.5%;ETR(Ⅱ)与ETR(Ⅰ)分别降低30.8%和28.9%。缺磷处理组Φ(Ⅱ)和ETR(Ⅱ)的降低幅度约为缺氮的1/2。这些定量研究结果对及时有效地诊断和区分羊草植物氮磷缺乏状况具有重要的参考价值。     

东北羊草草原主要植物热值

 对羊草(Aneurolepidium chinense)草原55种植物热值进行分析,高热值植物占总数的20％,中热值植物占58.18％,低热值植物占21.82％,55种植物全株平均热值为17949.45J·g-1。因含能物质在各器官的分配不同,同一植物不同器官的热值也存在着差异。务器官的平均热值花19399.28J·g-1>茎18022.58J·g-1>叶17885.17J·g-1>根17206.05J·g-1。不同科植物全株和各器官平均热值存在较大差异,即使同属植物也存在一定差异。菊科、禾本科和豆科3大科植物全株平均热值无明显差异,但豆科植物根的热值明显高于禾本科和菊科根的热值。     

东北羊草草原耐盐碱植物的研究

东北羊草草原的耐盐碱植物主要有１０种,分别属于藜科、禾本科和菊科,其生态分布与土壤中的ｐＨ值和电导率有密切关系。在１０种耐盐碱植物中,碱蓬、刺沙蓬、角碱蓬、翅碱蓬、碱蒿和碱地肤具有较大的细胞膜透性和对Ｎａ＋、Ｋ＋的富集能力,是重要的耐盐碱植物,在治理退化草原的过程中,有重要的应用价值。     

不同频率氮添加对内蒙古典型草原植物叶绿素的影响

大气氮沉降会影响植物功能性状的变异和进化,进而作用于植物个体和生态系统功能。研究草地生态系统植物功能性状在不同氮添加模式下的响应差异,对更准确地评估植物对环境变化的适应性至关重要。基于内蒙古草原野外长期氮沉降模拟实验平台,研究氮添加频率对优势物种羊草和冰草叶绿素含量的影响,结果表明每年一次氮添加使羊草叶绿素含量增加最多(15.21%),而每月一次氮添加对冰草叶绿素含量影响最大(增加了14.74%)。氮添加尤其是每年一次氮添加显著增加了土壤铵态氮、硝态氮和无机氮含量,并使土壤pH显著降低。这些结果表明:羊草叶绿素含量对低频率氮添加响应更明显,而高频率氮添加对冰草叶绿素含量的影响更显著,这两类物种间养分吸收策略存在明显差异。启示低频率氮添加可能高估了氮沉降对羊草叶绿素含量的影响,而低估了对冰草叶绿素含量的影响,这对准确预测植物叶片功能性状对大气氮沉降的变异具有重要意义,并将有助于应用到植物功能性状预测生态系统功能和过程响应未来全球变化的模型中。     

羊草草原群落植物种群结构的研究

中国科学院内蒙古草原生态系统定位研究站的宗旨是研究草原生态系统的结构、功能及其提高生产力的途径,羊草草原作为内蒙古典型草原区分布范围最广、面积最大的群系类型,研究羊草草原群落植物种群结构就有着明显的重要意义。     

利用调制荧光仪在线监测叶绿素荧光

介绍了利用便携式调制荧光仪PAM-2100在线监测叶绿素荧光的技术。该技术不影响植物的自然光合状态,司以在线监测Ft、F′m、Y、rETR、qP、qN或NPQ、PAR和叶温等指标。以凤眼莲为例进行了在线监测,每隔5min监测一次,共进行了225min的监测。结果表明叶绿索荧光参数的变化依赖于PAR的变化。Ft、rETR、qN和NPQ的变化与PAR的变化趋势一致,F′m、Y和qP的变化与PAR的变化相反。通过对风眼莲的在线监测,说明该技术是可靠的,具有简单、快速、灵敏等特点。随着新型调制荧光仪的出现,该技术可能在植物生态学领域得到广泛应用。     

富集钙磷的草原植物

在家畜营养中,钙磷的生理功能具有十分重要和密切的关系,它们常以磷酸钙的形式存在于骨骼中,其含量可占家畜矿物质总量的65％以上。对许多种家畜来说,不仅对钙磷含量的高低有一定要求,而且要求二者保持一定比例。一般来说,钙磷的正常比例多在2:1—1:1之间。假如家畜饲料中长期缺乏钙磷,或者这种比例不当,许多家畜表现出异食癖,奶牛产奶量下降,且易罗致软骨病。放牧家畜所需要的钙磷主要来自天然牧草,所以草原植物中钙磷的含量对家畜营养十分重要。     

内蒙古羊草草原群落主要植物的热值动态

对内蒙古羊草草原主要植物种群的干重热值动态研究表明,热值随植物种类,植物部位,取样时植物所处物候期及气候条件的不同而变化,羊草草原主要植物种群地上部分热值的变动范围在15703－18141J／g之间,其中灌木小叶锦鸡儿（Caragang microphylla)的热值最高,禾草类植物的热值多数较高,而大多数杂类草的热值相对较低,主要植物种群地下部分热值的分布范围为15051－16410J/g。其中根茎型草地下部分热值较高。不同种类植物地下部分热值差异并不与地上部分一致,根茎型禾草地上、地下部分热值差异较小,而须根型植物差异较在,不同种群的植物地上部分热值随植物候期的不同而波动,其变化规律是与植物种群本身的生物学特性相联系的,不同植物种群热值的年际小 规律有所不同,羊草（Leymus chinensis)、大针茅（Stipa grandis)和洽草（Koeloria cristata)的年际热值波动相关显著。但与生长季降水量和生长季累积日照时数之间无明显相关性,在某种程度上,植物热值的 种内变化反映了植物生长状况的差异。     

氮沉降和磷添加对杉木光合及叶绿素荧光特征的影响

为探讨杉木(Cunninghamia lanceolata)光合及叶绿素荧光参数在大气氮沉降和磷添加情况下的变化, 实验以10 龄杉木为研究对象, 共设9 个处理水平: 低氮(N30: 30 kg·ha-1·a-1), 高氮(N60: 60 kg·ha-1·a-1), 低磷(P20: 20 mg·kg-1), 高磷(P40: 40 mg·kg-1), 低氮低磷(N30 + P20), 低氮高磷(N30 + P40), 高氮低磷(N60 + P20), 高氮高磷(N60 + P40)和对照处理组(CK)。结果表明: 在夏季, 氮磷添加对杉木的最大净光合速率(Pn max)无显著影响。单独添加氮、磷都抑制了杉木的最大荧光产量(Fm)、初始荧光产量(F0)、PSII 潜在活性(Fv/F0)值; 单独添加磷促进了杉木的叶色值(SPAD); 在磷添加情况下, 低氮增加了杉木的Fm, 高氮增加了杉木的SPAD 值, 降低了杉木的非光化学淬灭系数(qN)值。在秋季, 单独添加氮促进了杉木的最大净光合速率。单独添加氮、磷抑制了杉木的SPAD 值。在磷添加情况下, 氮沉降增加了杉木的SPAD值, 降低了杉木的F0 值。夏季杉木叶片N 含量与SPAD呈显著正相关(p<0.01), 秋季杉木叶片N 含量与SPAD和光化学淬灭系数(qP)呈显著负相关(p<0.05), 而与Fm 和F0 呈显著正相关(p<0.05)。     

氮沉降强度和频率对羊草叶绿素含量的影响

氮沉降强度和沉降频率是决定其对陆地生态系统影响的重要决定因素。我们结合当前世界上各地区的氮沉降状况,设计了包括9个氮沉降梯度的长期控制实验,并将氮沉降分为两种沉降频率（一年2次和每月1次）、草原管理方式分为封育和割草两种。本文主要基于上述实验平台的优势植物（羊草）叶片叶绿素含量来探讨氮沉降方式（强度和频度）和草原管理方式（封育和打草）对草地生态系统结构和功能的影响。实验结果表明：1）氮沉降显著增加了植物叶片叶绿素含量（P < 0.001）;2）每月一次模拟氮沉降处理的植物叶绿素含量显著低于一年两次氮沉降的处理（P = 0.026）;3）在相同的氮沉降强度处理下,打草地相对于封育草地具有更高的叶绿素含量（P = 0.012）;4）羊草叶绿素含量与其叶片氮浓度显著正相关（P < 0.001）;5）羊草叶绿素含量与该植株高度极显著正相关（P < 0.001）。根据上述结果我们可以看出一年一次或一年两次的模拟氮沉降（类似于施肥处理或低频率的氮素添加实验）可能会夸大真实氮沉降对草地生态系统结构和功能的影响,今后在外推类似实验结论时应更加谨慎。此外,氮沉降下打草管理有利于增加了植物叶片叶绿素含量,可提高植物的光合作用,因此在未来氮沉降加剧状况下,打草可以保持或提高内蒙古草地生产力,有利于该地区草地的可持续利用。     

Leaf Gas Exchange and Chlorophyll Fluorescence Parameters in Phaseolus Vulgaris as Affected by Nitrogen and Phosphorus Deficiency

The effects of N and P deficiency, isolated or in combination, on leaf gas exchange and fast chlorophyll (Chl) fluorescence emission were studied in common bean cv. Negrito. 10-d-old plants grown in aerated nutrient solution were supplied with high N (HN, 7.5 mol m⁻³) or low N (LN, 0.5 mol m⁻³), and also with high P (HP, 0.5 mol m⁻³) or low P (LP, 0.005 mol m⁻³). Regardless of the external P supply, in LN plants the initial fluorescence (F₀) increased 12 % in parallel to a quenching of about 14 % in maximum fluorescence (F_m). As a consequence, the variable to maximum fluorescence ratio (F_v/F_m) decreased by about 7 %, and the variable to initial fluorescence ratio (F_v/F₀) was lowered by 25 % in relation to control plants. In LP plants, F_v/F_m remained unchanged whilst F_v/F₀ decreased slightly as a result of 5 % decline in F_m. Under N deficiency, the net photosynthetic rate (P _N) halved at 6 d after imposition of treatment and so remained afterwards. As compared to LN plants, P _N declined in LP plants latter and to a less extent. From 12 d of P deprivation onwards. P _N fell down progressively to display rates similar to those of LN plants only at the end of the experiment. The greater P _N in LP plants was not reflected in larger biomass accumulation in relation to LN beans. In general, P and N limitation affected photosynthesis parameters and growth without showing any synergistic or additive effect between deficiency of both nutrients. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Nitrogen Deficiency on Gas Exchange,Chlorophyll Fluorescence,and Antioxidant Enzymes in Leaves of Rice Plants

Gas exchange, chlorophyll (Chl) fluorescence, and contents of photosynthetic pigments, soluble proteins (ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO), and antioxidant enzymes were characterized in the fully expanded 6^th leaves in rice seedlings grown on either complete (CK) or on nitrogen-deficient nutrient (N-deficiency) solutions during a 20-chase period. Compared with the control plants, the lower photosynthetic capacity at saturation irradiance (P _max) was accompanied by an increase in intercellular CO₂ concentration (C_i), indicating that in N-deficient plants the decline in P _max was not due to stomatal limitation but due to the reduced carboxylation efficiency. The fluorescence parameters _PS2, F_v/F_m, electron transport rate (ETR), and q_P showed the same tendency as P _max in N-deficient plants. Correspondingly, a higher q_N paralleled the rise of the ratio of carotenoid (Car) to Chl contents. However, F_v/F_m was still diminished, suggesting that photoinhibition did occur in the photosystem 2 (PS2) reaction centres. In addition, the activities of antioxidant enzymes on a fresh mass basis were gradually lowered, leading to the aggravation of membrane lipid peroxidation with the proceeding N-deficiency. The accumulation of malonyldialdehyde resulted in the lessening of Chl and soluble protein content. Analyses of regression showed PS2 excitation pressure (1 - q_P) was linearly correlated with the content of Chl and inversely with soluble protein (particularly RuBPCO) content. There was a lag phase in the increase of PS2 excitation pressure compared to the decrease of RuBPCO content. Therefore, the increased excitation pressure under N-deficiency is probably the result of saturation of the electron transport chain due to the limitation of the use of reductants by the Calvin cycle. Rice plants responded to N-deficiency and high irradiance by decreasing light-harvesting capacity and by increasing thermal dissipation of absorbed energy.     

Sensitive Detection of Phosphorus Deficiency in Plants Using Chlorophyll a Fluorescence

Phosphorus (P) is a finite natural resource and an essential plant macronutrient with major impact on crop productivity and global food security. Here, we demonstrate that time-resolved chlorophyll a fluorescence is a unique tool to monitor bioactive P in plants and can be used to detect latent P deficiency. When plants suffer from P deficiency, the shape of the time-dependent fluorescence transients is altered distinctively, as the so-called I step gradually straightens and eventually disappears. This effect is shown to be fully reversible, as P resupply leads to a rapid restoration of the I step. The fading I step suggests that the electron transport at photosystem I (PSI) is affected in P-deficient plants. This is corroborated by the observation that differences at the I step in chlorophyll a fluorescence transients from healthy and P-deficient plants can be completely eliminated through prior reduction of PSI by far-red illumination. Moreover, it is observed that the barley (Hordeum vulgare) mutant Viridis-zb⁶³, which is devoid of PSI activity, similarly does not display the I step. Among the essential plant nutrients, the effect of P deficiency is shown to be specific and sufficiently sensitive to enable rapid in situ determination of latent P deficiency across different plant species, thereby providing a unique tool for timely remediation of P deficiency in agriculture.The world population is estimated to exceed 9 billion people by 2050. This means that agriculture on a global scale has to increase food production by 70% to 100%, and, at the same time, handle the consequences of global climate changes and reduce its environmental footprint (Food and Agriculture Organization of the United Nations, 2009; Godfray et al., 2010; Foley et al., 2011). A major challenge related to this is the supply and use of phosphorus (P) to support future plant production (Cordell et al., 2009; Gilbert, 2009; MacDonald et al., 2011).P is an essential plant nutrient, which means that plants require P in adequate amounts to fulfill a complete lifecycle. It has been estimated that 30% of the world’s agricultural soils are P deficient and need fertilizer addition to ensure yield and quality (MacDonald et al., 2011). However, phosphate rock, the main source of P fertilizers, is a finite natural resource, and the known rock phosphate reserves are estimated to last as little as 50 years in the gloomiest forecasts (Gilbert, 2009; Edixhoven et al., 2013). This makes P a potential strategic natural resource similar to oil, as very few countries control the vast majority of the known reserves (Gilbert, 2009; Elser and Bennett, 2011; Edixhoven et al., 2013). Presently, an immense overuse of P is found in some parts of the world, causing eutrophication of lakes and seas, while P depletion results in severe yield limitations elsewhere (MacDonald et al., 2011; Obersteiner et al., 2013). An essential aspect of solving both of these problems is to increase P use efficiency in agriculture, thus reducing the negative environmental impact of agriculture and helping to ensure a sustainable use of P resources while increasing the worldwide food production (Schröder et al., 2011; Veneklaas et al., 2012).Here, we present a unique analytical principle based on chlorophyll a fluorescence that allows rapid, nondestructive, onsite assessment of plant P status by recording the so-called OJIP transient of a dark-adapted leaf.When a chlorophyll molecule absorbs light, one of three events will occur: The light may be used to drive photosynthesis, it can be dissipated as heat, or it can be reemitted as fluorescence. Less than 10% of light absorbed by the plant causes emission of chlorophyll a fluorescence (Govindjee, 2004; Stirbet and Govindjee, 2011). When a dark-adapted leaf is exposed to saturating actinic light, the resulting time-dependent fluorescence forms a so-called Kautsky curve (Kautsky and Hirsch, 1931; McAlister and Myers, 1940). Within 300 ms, the fluorescence increases from a minimum level (F₀) to the maximum level. If measured with a sufficiently high time resolution, a polyphasic transient with four distinct steps, designated as O, J, I, and P, is observed. After reaching maximum intensity at the P step, the fluorescence intensity declines until it reaches a steady state within a few minutes (Harbinson and Rosenqvist, 2003; Govindjee, 2004).The physiological mechanisms underlying the polyphasic OJIP transient are still not clarified, but it is believed that the J and I steps represent dynamic bottlenecks in the photosynthetic electron transport chain. The first rise (2 ms) from O to J is referred to as the photochemical phase due to its dependence on the intensity of the incoming light. This phase is assumed to reflect the reduction of the primary quinone electron acceptor in PSII (Stirbet and Govindjee, 2011). The reduction of the primary quinone electron acceptor results in a decreased electron trapping efficiency and therefore an increase in the dissipation of absorbed light energy by fluorescence and heat. The second part, from J over I to P, is called the thermal phase due to its temperature sensitivity. This phase is much slower than the first, and it is believed that the J-I phase primarily reflects a sequential reduction of the remaining plastoquinone pool of PSII and that the I-P phase reflects the subsequent electron flow through cytochrome b₆f to electron sinks at the PSI acceptor side (Stirbet and Govindjee, 2011). Thus, the OJIP transient resembles a titration of the photochemical quantum yield and reflects the complex electron transport properties of PSII and PSI.Consistent with their known influence on photosynthesis, deficiencies of essential plant nutrients such as Fe, Cu, Mg, Mn, and S have previously been shown to affect OJIP transients (Kastori et al., 2000; Mallick and Mohn, 2003; Larbi et al., 2004; Husted et al., 2009; Tang et al., 2012; Yang et al., 2012). As a consequence, several attempts have been made to identify nutrient imbalances and disorders using one or several parameters derived from the transients, but apart from Mn (Husted et al., 2009; Schmidt et al., 2013), attempts have not been successful in terms of sensitivity and specificity. This includes P, which previously has been reported to have an effect on OJIP transients, yet the reported effects seem mutually contradictory and nonspecific to P (Ripley et al., 2004; Weng et al., 2008; Jiang et al., 2009; Lin et al., 2009).Here, we present the unique finding that increasing levels of P deficiency affect the shape of the OJIP transient around the I step at 20 to 50 ms and causes the I step to gradually straighten and disappear. It is demonstrated that this effect is fully reversible and, among the essential plant nutrients, specific for P deficiency using both monocotyledons (barley [Hordeum vulgare]) and dicotyledons (tomato [Solanum lycopersicum]) plant species. Furthermore, it is shown that it is possible to determine whether a plant is P sufficient or deficient and to quantitatively predict the P concentration in leaf tissue using multivariate analysis of the OJIP transients.     

Assessment of Photosynthetic Performance of Prochloron in Lissoclinum patella in hospite by Chlorophyll Fluorescence Measurements

Two new PAM fluorometers (pulse amplitude modulated) were usedin an investigation of photosynthetic performance of Prochloronresident as a symbiont in the ascidian Lissoclinum patella,growing in a coral reef of Heron Island on the Great BarrierReef. With a new DIVING-PAM in situ measurements of effectivePSII quantum yield (     

State Transitions in the Green Alga Scenedesmus Obliquus Probed by Time-Resolved Chlorophyll Fluorescence Spectroscopy and Global Data Analysis

Decay-associated fluorescence spectra of the green alga Scenedesmus obliquus have been measured by single-photon timing with picosecond resolution in various states of light adaptation. The data have been analyzed by applying a global data analysis procedure. The amplitudes of the decay-associated spectra allow a determination of the relative antenna sizes of the photosystems. We arrive at the following conclusions: (a) The fluorescence kinetics of algal cells with open PS II centers (F₀ level) have to be described by a sum of three exponential components. These decay components are attributed to photosystem (PS) I (τ ≈ 85 ps, λ_max^em ≈ 695-700 nm), open PS II α-centers (τ ≈ 300 ps, λ_max^em = 685 nm), and open PS II β-centers (τ ≈ 600 ps, λ_max^em = 685 nm). A fourth component of very low amplitude (τ ≈ 2.2-2.3 ns, λ_max^em = 685 nm) derives from dead chlorophyll. (b) At the F_max level of fluorescence there are also three decay components. They originate from PS I with properties identical to those at the F₀ level, from closed PS II α-centers (τ ≈ 2.2 ns, λ_max^em = 685 nm) and from closed PS β-centers (τ ≈ 1.2 ns, λ_max^em = 685 nm). (c) The major effect of light-induced state transitions on the fluorescence kinetics involves a change in the relative antenna size of α- and β-units brought about by the reversible migration of light-harvesting complexes between α-centers and β-centers. (d) A transition to state II does not measurably increase the direct absorption cross-section (antenna size) of PS I. Our data can be rationalized in terms of a model of the antenna organization that relates the effects of state transitions and light-harvesting complex phosphorylation with the concepts of PS II α,β-heterogeneity. We discuss why our results are in disagreement with those of a recent lifetime study of Chlorella by M. Hodges and I. Moya (1986, Biochim. Biophys. Acta., 849:193-202).     

Photosynthesis and Chlorophyll Fluorescence in Two Hybrids of Sorghum under Different Nitrogen and Water Regimes

In two hybrids of sorghum (Sorghum bicolor Moench.), C51 and C42, high nitrogen concentration (HN) increased net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) of well watered (HW) plants. Water stressing (LW plants) resulted in low PN, gs, and E in both hybrids, but the values were still higher in HN plants as compared to low nitrogen-grown (LN) plants. Intercellular CO2 concentration (Ci) increased in droughted plants. This increase was much higher in LN plants as compared to HN plants. Instantaneous water use efficiency was lower in LN plants as a consequence of a greater effect of water stress on photosynthesis. Leaf water potential was reduced by water stress in all treatments. Analysis of chlorophyll a fluorescence at room temperature showed that photosystem 2 (PS2) was rather tolerant to the water stress imposed. Water stress caused a slight decrease in the efficiency of excitation capture by open PS2 reaction centres (Fv/Fm). The in vivo quantum yield of PS2 photochemistry (PS2) and the photochemical quenching coefficient (qP) were slightly reduced, while the nonphotochemical quenching coefficient (qN) was increased under the water stress. However, in hybrid C42 these characters were little or not affected by the water stress.     

氮素水平对不同品种茶树光合及叶绿素荧光特性的影响

为探明氮素水平对不同品种茶树的光合系统的影响机制,以‘福鼎大白茶’、‘保靖黄金茶1号’、‘白毫早’两年生茶苗为材料,设置不施氮N_0(0g)、低氮N_1(11g)、中氮N_2(22g)和高氮N_3(33g)4个氮素[(NH_4)_2SO_4]水平的盆栽实验,研究了铵态氮对3个品种茶树的生长势、叶片叶绿素含量、光合参数与叶绿素荧光参数的影响。结果表明:(1)施氮处理能够显著促进茶树的生长,提高茶树叶片叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr),降低胞间CO_2浓度(Ci),并以N_2处理最好,但水分利用率(WUE)在3个品种茶树间表现不同。(2)在N_2处理下,3个茶树品种的叶片光系统Ⅱ(PSⅡ)暗适应下的最大光化学效率(F_v/F_m)、光化学猝灭系数(qP)、PSⅡ的相对电子传递速率(rETR)亦增加最大,非光化学淬灭系数(NPQ)降低。(3)茶树叶片叶绿素含量与光合参数间存在着一定的联系,并且具有品种特异性。研究发现,适量施氮能够显著增加茶树叶绿素含量、气孔导度、光合活性,从而使得各品种茶树净光合速率增加;氮素水平对各茶树品种的光合及荧光特性影响存在差异,水分利用率亦具有品种特异性;生产中应综合叶绿素含量、光合作用参数、叶绿素荧光参数,可快速、直观地评价不同品种茶树对氮素营养的内在需求,为茶园施肥管理提供指导。     

超氧阴离子诱导的叶绿素荧光猝灭

分别通过黄嘌呤(X)与黄嘌呤氧化酶(XO)反应和甲基紫金(MV)的作用,观察了O·-2诱导莴苣叶绿体的叶绿素荧光猝灭过程.结果表明,O-·2的产生明显使光化学猝灭(qP)和非光化学猝灭(qN)增加.叶绿体内SOD被DDC抑制后,X+XO诱导的叶绿素荧光猝灭过程中,qP下降,qN上升;MV诱导的叶绿素荧光猝灭过程中,qP上升幅度不大,qN增加不明显.当碳代谢被碘乙酰胺(JAA)抑制后, qP下降,qN上升.解偶联剂NH4Cl增加质子跨类囊体膜的通透性,导致qP增加和qN降低,加入MV后qP和qN增加不明显.分析认为,-·2的产生和及时被清除对保持光合电子传递和增加跨膜ΔpH有很重要的作用,有利于叶绿体吸收的光能得到转化和耗散,在一定程度上减轻过量光能引起的光抑制损伤.     

不同水氮梯度下典型挺水植物叶绿素荧光的响应特性

叶绿素荧光测量分析可以揭示植物叶片光化学效率的变化,已越来越多地应用于植物生态监测。以再生水为主要补给水源的北京门城湖湿地公园为研究区,选取典型湿地挺水植物芦苇(Phragmites australis)、香蒲(Typha angustifolia)和茭白(Zizania latifolia)为研究对象,通过野外测量叶片尺度的叶绿素荧光参数和室内测定对应样点的水体总氮含量指标,研究了再生水补给条件下,不同水氮梯度植物叶绿素荧光的响应特性。结果表明,3种典型挺水植物的初始荧光(Fo)与最大荧光(Fm)随着水体总氮含量的增加呈现上升的趋势;PSII的量子效率(F_v/F_m)与实际量子效率(ΦPSII)受水氮含量的影响先升高,达到15–20 mg·L~(–1)区间时,则与之持平;光化学淬灭(qP)参数则呈现先升高后降低的变化趋势,而非光化学淬灭(NPQ)参数的变化没有明显的规律。当水氮含量为15–20 mg·L~(–1)时,光化学反应减弱,光合作用出现抑制。不同类型植物的荧光参数也有所不同,处于生长期(6月)植物的光合作用显著强于生长成熟期(9月)。