鄂尔多斯高原碱湖的钝顶螺旋藻光合生理研究

鄂尔多斯高原碱湖的钝顶螺旋藻光合色素含量高低排列为藻胆素>叶绿素a>类胡萝卜素;各色素具有特定的吸收光谱,活体吸收光谱体现出了各色素的吸收;各色素的荧光发射主峰波长约长于活体的13￣35nm,相对荧光强度约是活体的11倍。其光合速率的日变化呈单峰曲线,13:00时达到最高;光补偿点为28￣30μmol.m-2.s-1;光饱和点为220￣235μmol.m-2.s-1;光合作用的最适温度为35℃。呼吸速率日变化随温度的升高呈缓慢上升的趋势。     

水稻亚种间杂种F1光合特性研究

用绵恢725、蜀恢527和蜀恢881三个籼型恢复系、1个美国稻Lemont和1个爪哇稻香大粒作母本,与1个日本特早熟粳稻Kitaake杂交,研究了5个杂种F1及其亲本的光合生理表现.结果表明,在高光通量密度(Photosynthetic flux density,PFD)条件下,5个杂种F1净光合速率(Pn)明显高于双亲或双亲之一,推测亲本与杂种F1之间不同的Pn同叶片中Rubsico活性有关.杂种F1的比较中,在表观量子效率(ψ)、羧化效率(CE)、CO2补偿点(T)等方面,籼粳亚种间杂种F1(绵恢725/Kitaake、蜀恢527/Kitaake、蜀恢881/Kitaake)对2个亚种内杂种F1香大粒/Kitaake(粳爪交)、Lemont/Kitaake(不同生态型的粳粳交,美国稻属于特殊粳稻)具有明显的优势,而蜀恢881含有粳型血缘,蜀恢881/Kitaake也比典型籼粳亚种间杂种F1绵恢725/Kitaake、蜀恢527/Kitaake优势稍逊一筹.5个杂种F1因为具有不同的遗传差异而表现出不同的光合优势,在这方面,典型籼粳亚种间杂交蜀恢527/Kitaake、绵恢725/Kitaake要优于其他杂交种,说明亲本间遗传差异越大,其杂种F1的光合优势越强.     

An improved analysis of forest carbon dynamics using data assimilation

There are two broad approaches to quantifying landscape C dynamics – by measuring changes in C stocks over time, or by measuring fluxes of C directly. However, these data may be patchy, and have gaps or biases. An alternative approach to generating C budgets has been to use process‐based models, constructed to simulate the key processes involved in C exchange. However, the process of model building is arguably subjective, and parameters may be poorly defined. This paper demonstrates why data assimilation (DA) techniques – which combine stock and flux observations with a dynamic model – improve estimates of, and provide insights into, ecosystem carbon (C) exchanges. We use an ensemble Kalman filter (EnKF) to link a series of measurements with a simple box model of C transformations. Measurements were collected at a young ponderosa pine stand in central Oregon over a 3‐year period, and include eddy flux and soil CO₂ efflux data, litterfall collections, stem surveys, root and soil cores, and leaf area index data. The simple C model is a mass balance model with nine unknown parameters, tracking changes in C storage among five pools; foliar, wood and fine root pools in vegetation, and also fresh litter and soil organic matter (SOM) plus coarse woody debris pools. We nested the EnKF within an optimization routine to generate estimates from the data of the unknown parameters and the five initial conditions for the pools. The efficacy of the DA process can be judged by comparing the probability distributions of estimates produced with the EnKF analysis vs. those produced with reduced data or model alone. Using the model alone, estimated net ecosystem exchange of C (NEE)=?251±197 g C m^?2 over the 3 years, compared with an estimate of ?419±29 g C m^?2 when all observations were assimilated into the model. The uncertainty on daily measurements of NEE via eddy fluxes was estimated at 0.5 g C m^?2 day^?1, but the uncertainty on assimilated estimates averaged 0.47 g C m^?2 day^?1, and only exceeded 0.5 g C m^?2 day^?1 on days where neither eddy flux nor soil efflux data were available. In generating C budgets, the assimilation process reduced the uncertainties associated with using data or model alone and the forecasts of NEE were statistically unbiased estimates. The results of the analysis emphasize the importance of time series as constraints. Occasional, rare measurements of stocks have limited use in constraining the estimates of other components of the C cycle. Long time series are particularly crucial for improving the analysis of pools with long time constants, such as SOM, woody biomass, and woody debris. Long‐running forest stem surveys, and tree ring data, offer a rich resource that could be assimilated to provide an important constraint on C cycling of slow pools. For extending estimates of NEE across regions, DA can play a further important role, by assimilating remote‐sensing data into the analysis of C cycles. We show, via sensitivity analysis, how assimilating an estimate of photosynthesis – which might be provided indirectly by remotely sensed data – improves the analysis of NEE.     

Evaluation of genotoxic effects of Apitol (cymiazole hydrochloride) in vitro by measurement of sister chromatid exchange

Apitol^®, with cymiazole hydrochloride as the active ingredient, is used in bee-keeping against the ectoparasitic mite Varroa destructor. The preparation was evaluated for genotoxicity in cultured human peripheral blood lymphocytes. Sister chromatid exchange, the mitotic index and the cell proliferation index were determined for three experimental concentrations of Apitol^® (0.001, 0.01 and 0.1 mg/ml). All concentrations significantly (p < 0.001) increased the mitotic index (MI = 7.35 ± 0.18%, 8.31 ± 0.20% and 12.33 ± 0.25%, respectively), the proliferative index (PI = 1.83 ± 0.01, 1.84 ± 0.01 and 1.88 ± 0.02, respectively) and the frequency of sister chromatid exchange (SCE = 8.19 ± 1.81, 8.78 ± 1.80 and 13.46 ± 1.88, respectively), suggesting that cymiazole hydrochloride has genotoxic potential.     

Carbon fluxes from a tropical peat swamp forest floor

A tropical ombrotrophic peatland ecosystem is one of the largest terrestrial carbon stores. Flux rates of carbon dioxide (CO₂) and methane (CH₄) were studied at various peat water table depths in a mixed‐type peat swamp forest floor in Central Kalimantan, Indonesia. Temporary gas fluxes on microtopographically differing hummock and hollow peat surfaces were combined with peat water table data to produce annual cumulative flux estimates. Hummocks formed mainly from living and dead tree roots and decaying debris maintained a relatively steady CO₂ emission rate regardless of the water table position in peat. In nearly vegetation‐free hollows, CO₂ emission rates were progressively smaller as the water table rose towards the peat surface. Methane emissions from the peat surface remained small and were detected only in water‐saturated peat. By applying long‐term peat water table data, annual gas emissions from the peat swamp forest floor were estimated to be 3493±316 g CO₂ m^?2 and less than 1.36±0.57 g CH₄ m^?2. On the basis of the carbon emitted, CO₂ is clearly a more important greenhouse gas than CH₄. CO₂ emissions from peat are the highest during the dry season, when the oxic peat layer is at its thickest because of water table lowering.     

Effects of water stress and high nocturnal temperature on photosynthesis and nitrogen level of a perennial grass Leymus chinensis

Water deficit and high temperature are important environmental factors restricting plant growth and photosynthesis. The two stresses often occur simultaneously, but their interactions on photosynthesis and nitrogen level have been less studied. In the present experiment, we measured photosynthetic parameters, stomatal density, and nitrogen levels, as well as soluble sugar content of leaves of a perennial grass, Leymus chinensis, experiencing two day/night temperature regimes of 30/20 °C and 30/25 °C, and five different soil moisture contents (the soil relative-water content ranged from 80% to 25%). Leaf relative water content, leaf biomass, whole plant biomass, the ratio between the leaf biomass and total plant biomass, and the photosynthetic rate, as well as water-use efficiency decreased at high night temperature, especially under severe water stress conditions. Stomatal index was also increased by soil water stress except very severe water stress, and high nocturnal temperature decreased the leaf stomatal index under soil water stress. Nocturnal warming decreased nitrogen concentration in the leaves and increased it in the roots, particularly when plants were subjected to severe water stress. There were significant positive correlations between the photosynthetic rate and both soluble sugar concentration and nitrogen concentration at low nocturnal temperature. It is suggested that nocturnal warming significantly exacerbates the adverse effects of soil water stress, and their synergistic interactions might reduce the plant productivity and constrain its distribution in the region dominated by L. chinensis, based on predictions of global climate change.     

Assessment of Phytotoxicity of Chromium in Flooded Soils using Embedded Selective Ion Exchange Resin Method

Chromium present in the forms of Cr(VI) or Cr(III) in soils. Since the toxicity and mobility of Cr(VI) are higher than those of Cr(III), it would be important to estimate soil Cr(VI) accurately in order to assess the phytotoxicity of Cr. Soil redox potential can influence the distribution of Cr between Cr(VI) and Cr(III) forms, and thus an in situ method which is not affected by the soil redox condition is needed for determining Cr(VI) availability in paddy fields. In this study, the Cu-saturated selective ion exchange resin (DOWEX M4159), serving as an infinite sink, was embedded in soils to extract available Cr(VI) from three representative saturated soils with different amounts of Cr(VI). The results suggested that Cr(VI) reduction occurred in the flooded soils, and the acid environment favored the adsorption and reduction of Cr(VI). There was a significant dose-response relationship between the soil resin-extractable Cr(VI) and the plant height of rice seedlings for test soils. The experimental results suggested that the embedded selective ion exchange resin method could be a suitable in situ method for assessing the phytotoxicity of Cr in flooded soils.     

The Biogeochemistry of Carbon at Hubbard Brook

The biogeochemical behavior of carbon in the forested watersheds of the Hubbard Brook Experimental Forest (HBEF) was analyzed in long-term studies. The largest pools of C in the reference watershed (W6) reside in mineral soil organic matter (43% of total ecosystem C) and living biomass (40.5%), with the remainder in surface detritus (14.5%). Repeated sampling indicated that none of these pools was changing significantly in the late-1990s, although high spatial variability precluded the detection of small changes in the soil organic matter pools, which are large; hence, net ecosystem productivity (NEP) in this 2nd growth forest was near zero (± about 20 g C/m²-yr) and probably similar in magnitude to fluvial export of organic C. Aboveground net primary productivity (ANPP) of the forest declined by 24% between the late-1950s (462 g C/m²-yr) and the late-1990s (354 g C/m²-yr), illustrating age-related decline in forest NPP, effects of multiple stresses and unusual tree mortality, or both. Application of the simulation model PnET-II predicted 14% higher ANPP than was observed for 1996–1997, probably reflecting some unknown stresses. Fine litterfall flux (171 g C/m²-yr) has not changed much since the late-1960s. Because of high annual variation, C flux in woody litterfall (including tree mortality) was not tightly constrained but averaged about 90 g C/m²-yr. Carbon flux to soil organic matter in root turnover (128 g C/m²-yr) was only about half as large as aboveground detritus. Balancing the soil C budget requires that large amounts of C (80 g C/m²-yr) were transported from roots to rhizosphere carbon flux. Total soil respiration (TSR) ranged from 540 to 800 g C/m²-yr across eight stands and decreased with increasing elevation within the northern hardwood forest near W6. The watershed-wide TSR was estimated as 660 g C/m²-yr. Empirical measurements indicated that 58% of TSR occurred in the surface organic horizons and that root respiration comprised about 40% of TSR, most of the rest being microbial. Carbon flux directly associated with other heterotrophs in the HBEF was minor; for example, we estimated respiration of soil microarthropods, rodents, birds and moose at about 3, 5, 1 and 0.8 g C/m²-yr, respectively, or in total less than 2% of NPP. Hence, the effects of other heterotrophs on C flux were primarily indirect, with the exception of occasional irruptions of folivorous insects. Hydrologic fluxes of C were significant in the watershed C budget, especially in comparison with NEP. Although atmospheric inputs (1.7 g C/m²-yr) and streamflow outputs (2.7 g C/m²-yr) were small, larger quantities of C were transported within the ecosystem and a more substantial fraction of dissolved C was transported from the soil as inorganic C and evaded from the stream as CO₂ (4.0 g C/m²-yr). Carbon pools and fluxes change rapidly in response to catastrophic disturbances such as forest harvest or major windthrow events. These changes are dominated by living vegetation and dead wood pools, including roots. If biomass removal does not accompany large-scale disturbance, the ecosystem is a large net source of C to the atmosphere (500–1200 g C/m²-yr) for about a decade following disturbance and becomes a net sink about 15–20 years after disturbance; it remains a net sink of about 200–300 g C/m²-yr for about 40 years before rapidly approaching steady state. Shifts in NPP and NEP associated with common small-scale or diffuse forest disturbances (e.g., forest declines, pathogen irruptions, ice storms) are brief and much less dramatic. Spatial and temporal patterns in C pools and fluxes in the mature forest at the HBEF reflect variation in environmental factors. Temperature and growing-season length undoubtedly constrain C fluxes at the HBEF; however, temperature effects on leaf respiration may largely offset the effects of growing season length on photosynthesis. Occasional severe droughts also affect C flux by reducing both photosynthesis and soil respiration. In younger stands nutrient availability strongly limits NPP, but the role of soil nutrient availability in limiting C flux in the mature forest is not known. A portion of the elevational variation of ANPP within the HBEF probably is associated with soil resource limitation; moreover, sites on more fertile soils exhibit 20–25% higher biomass and ANPP than the forest-wide average. Several prominent biotic influences on C pools and fluxes also are clear. Biomass and NPP of both the young and mature forest depend upon tree species composition as well as environment. Similarly, litter decay differs among tree species and forest types, and forest floor C accumulation is twice as great in the spruce–fir–birch forests at higher elevations than in the northern hardwood forests, partly because of inherently slow litter decay and partly because of cold temperatures. This contributes to spatial patterns in soil solution and streamwater dissolved organic carbon across the Hubbard Brook Valley. Wood decay varies markedly both among species and within species because of biochemical differences and probably differences in the decay fungi colonizing wood. Although C biogeochemistry at the HBEF is representative of mountainous terrain in the region, other sites will depart from the patterns described at the HBEF, due to differences in site history, especially agricultural use and fires during earlier logging periods. Our understanding of the C cycle in northern hardwood forests is most limited in the area of soil pool size changes, woody litter deposition and rhizosphere C flux processes.     

Auswahl von GC-Phasen und Optimierung von Trichothecen-Trennungen mittels Computersimulation

Gas chromatography combines high resolution with good sensitivity (ECD) for the simultaneous analysis of trichothecenes. With the aid of computer-supported GC simulation based on thermodynamic retention indices, optimized GC methods for 4 different phase polarities have been developed. The verification with polar and unpolar columns in 2 GCs under optimized separation conditions provides highly reliable results.

Presented at the 26^th Mykotoxin-Workshop in Herrsching, Germany, May 17–19, 2004     

Seasonal production of moulting hormone in the barnacle Semibalanus balanoides

An analytical procedure for the quantification of ecdysteroids (crustacean moulting hormone) in barnacles was devised so that minimum sample size could be used. A combination of solvent partitions, Sephadex chromatography, silylation and gas chromatography with electron capture detection was devised, enabling ecdysteroids to be determined down to 20 pg. This was used to determine the amount of moulting hormone in a population of barnacles over a 30 month period. Levels varied from barely detectable in winter months to a maximum value of 1.5 μg kg^− 1 of wet weight of barnacles in September. Polar conjugates of 20-hydroxyecdysone were detected only during the winter months. The number of barnacles moulting at any time corresponded roughly to the titre of hormone present at that time.