叶龄及树冠不同部位光强对黄花梨光合速率的影响

笔者以黄花梨为试材,研究了叶龄及树冠不同部位光强对其光合速率的影响。结果表明:黄花梨叶片在展叶后约11天即有少量光合产物输出,25天时,单叶净光合速率接近最大值;密植梨树高光合叶幕厚度约125cm左右。     

矮嵩草草甸植物蒸腾强度的初步研究

 此项研究工作于1986年5—9月植物生长季节内,在海北高寒草甸生态系统定位站进行。用钴纸法测定了矮嵩草等10种植物的蒸腾强度、垂穗披碱草等3种植物的蒸腾日进程和不同植被覆盖地段的蒸腾—蒸发量,在测定时记录了气温、湿度等有关气象资料,以便分析。研究结果表明：1．矮嵩草等10种植物的蒸腾强度随植物种和所处的物候期而变化,植物生长早期蒸腾强度较低,进入生殖阶段,蒸腾强度明显提高。2．垂穗披碱草等3种植物蒸腾强度日进程呈明显的单峰型曲线,在中午或午后出现峰值,没有午休现象。这同气孔一直开着有关,是矮嵩草草甸植物蒸腾的特征之一。 3．不同植被覆盖地段的蒸腾—蒸发表明,有植被覆盖的地段的蒸腾—蒸发量较裸地的蒸发量为高。     

鲢、鳙在天然条件下的摄食强度(Ⅱ)武汉东湖鲢、鳙周年摄食强度的研究

武汉东湖的鲢(Hypophthalmichthy molitrix)鳙(Aristichthys nobilis)在天然条件下摄食强度具季节性变化。摄食强度高峰处于夏季,低谷处于冬季。在实验条件下,按周年采样期间水温变化范围,测定鱼的肠管排空率。食物通过鱼肠管时间(Y_p—h)与水温(X_t—℃)的关系为: 鲢Y_p=270.63 X_t~(0.6408) 鳙Y_p=280.46 X_t~(0.6642) 根据修正后Bajkov公式(D=C (24.A)/n),估算鱼的日粮。鱼日粮(Y_D)与水温(X_t)关系为: 鲢Y_D=0.2683e~(0.1503X_t) 鳙Y_D=0.0075X_t~(2.2715) 计算鱼在天然条件下周年月粮及年粮。鲢、鳙对天然饵料年消耗量分别为18.924公斤及17.39公斤,饵料系数分别为18.02及13.38。     

Zn buffering capacity and Zn accumulation in Swiss chard for some sludge-amended soils

Zinc sorption by soils can greatly affect its availability to plants. This study was conducted to determine the relationship between the Zn sorption capacity and plant Zn accumulation in five sludge-amended soils using Swiss chard (Beta vulgaris L.) as an indicator plant. Zinc sorption as a function of Zn concentration and pH was determined for the soils which received no sludge amendment; also DTPA (diethylenetriaminepentaacetic acid) extractable Zn was determined in all soils. Whereas the responses of DTPA-Zn and plant Zn to pH and the quantities of Zn sorbed were similar, the logarithm of DTPA-Zn accounted for only 82% of the variability in the logarithm of Zn accumulation by the plants. The variability was better explained when pH was included with DTPA-Zn in stepwise multiple regressions. The Zn buffering capacity, defined as the ratio of the change in quantity of Zn sorbed ( Zn_s) to the change in Zn solution concentration (Zn₁) (or Zn_s/Zn₁), and the estimated quantity of Zn sorbed were used as a basis to measure Zn intensity. Zinc intensity, which reflects Zn solution concentration, was the predominant factor controlling Zn accumulation by Swiss chard, judging from the good fit of the values of both parameters to the Michaelis-Menten equation. The maximum Zn accumulation was approximately 9 mmol kg^–1.Scientific paper no. 8901-29, Department of Agronomy and Soils, College of Agriculture and Home Economics Research Center. Washington State University, Pullman, WA 99164, USA.Scientific paper no. 8901-29, Department of Agronomy and Soils, College of Agriculture and Home Economics Research Center. Washington State University, Pullman, WA 99164, USA.     

Water-storage capacity ofThuja,Tsuga andAcer stems measured by dehydration isotherms

Water-storage capacity was measured inThuja occidentalis L.,Tsuga canadensis (L.) Carr., andAcer saccharum Marsh. during the dehydration of stem segments 1.5–2.5 cm in diameter. Stem water potential was measured with a temperature-corrected stem hygrometer and cavitations were detected acoustically. Water loss was measured by weight change. Dehydration isotherms consistently displayed three phases. The first phase, from water potential (Ψ) 0 to about −0.2 MPa, had a high capacitance (C>0.4kg water lost· (1 of tissue)⁻¹· MPa⁻¹) and we have attributed this high C to capillary water as defined by Zimmermann (1983, Xylem structure and the ascent of sap, Springer-Verlag). The second phase from Ψ=−0.5 to about −2.0 had the lowest C values (<0.02 kg·l⁻¹·MPa⁻¹) and was accompanied by a few cavitation events. This phase may have been a transition zone between capillary storage and water released by cavitation events as well as water drawn from living cells of the bark. The third phase also had a high C (about 0.07–0.22kg·l⁻¹·MPa⁻¹) and was associated with many cavitation events while Ψ declined below about −2.5 MPa; we presume the high capacitance was the consequence of water released by cavitation events. We discuss the ecological adaptive advantage of these three phases of water-storage in trees. In moist environments, water withdrawn from capillary storage may be an important fraction of transpiration, but may be of little adaptive advantage. For most of the growth season trees draw mainly on elastic storage, but stem elastic storage is less than leaf elastic storage and therefore unlikely to be important. In very dry environments, water relased by cavitation events might be important to the short-term survival of trees.     

Effects of light, temperature, gibberellin (GA3) and their interaction on coleoptile and leaf elongation of tall, semi-dwarf and dwarf wheat

Near-isogenic wheat lines differing in height-reducing (Rht) alleles, in each of two cultivars, were used to investigate the effects of light intensity and of their interaction with temperature and GA₃ application, on the elongation of the coleoptile and the first seedling leaf. Darkness caused a conspicuous increase in the lengths of the coleoptile and of the sheath and lamina of the first leaf, in GA₃ treated and untreated seedlings of all genotypes grown at 11 and 25°C. The genotype effects and the effects of light intensity and GA₃ application on leaf length were ascribed entirely to their effects on the rate of leaf elongation since the duration of leaf elongation was not affected by these factors. Temperature elevation from 11 to 25°C caused a 55% shortening of the duration of leaf elongation and a concomitant increase in elongation rate, which diminished with increased genotypic dwarfness. Accordingly, temperature elevation resulted in a significant reduction in leaf-length of the light-grown dwarf genotypes and the dark-grown dwarf and semi-dwarf genotypes. It is suggested that this temperature × light × genotype interaction effect is due to environmental dependent upper limits of elongation rate set by the Rht alleles.Abbreviations PAR Photosynthetic Active Radiation     

Effect of maximal arm exercise on skin blood flux in the paralyzed lower limbs in persons with spinal cord injury

The purpose of the present study was to examine the effect of maximal arm exercise on the skin blood circulation of the paralyzed lower limbs in persons with spinal cord injury (PSCI). Eight male PSCI with complete lesions located between T3 and L1 performed graded maximal arm-cranking exercise (MACE) to exhaustion. The skin blood flux at the thigh (SBFT) and that at the calf (SBFC) were monitored using laser-Doppler flowmeter at rest and for 15 s immediately after the MACE. The subject's mean peak oxygen uptake and peak heart rate was 1.41 ± 0.22 1·min⁻¹ and 171.6 ± 19.2 beats·min⁻¹, respectively. No PSCI showed any increase in either SBFT or SBFC after the MACE, when compared with the values at rest. These results suggest that the blood circulation of the skin in the paralyzed lower limbs in PSCI is unaffected by the MACE.     

Fluorescence correlation spectroscopy with high count rate and low background: analysis of translational diffusion

An epi-illuminated microscope configuration for use in fluorescence correlation spectroscopy in bulk solutions has been analyzed. For determining the effective sample dimensions the spatial distribution of the molecule detection efficiency has been computed and conditions for achieving quasi-cylindrical sample shape have been derived. Model experiments on translational diffusion of rhodamine 6G have been carried out using strong focusing of the laser beam, small pinhole size and an avalanche photodiode in single photon counting mode as the detector. A considerable decrease in background light intensity and measurement time has been observed. The background light is 40 times weaker than the fluorescence signal from one molecule of Rh6G, and the correlation function with signal-to-noise ratio of 150 can be collected in 1 second. The effect of the shape of the sample volume on the autocorrelation function has been discussed. Correspondence to: R. Rigler     

Extra-weak chemiluminescence of drugs XV. Method for determining stability of Toki-shakuyaku-san extract granules

The purpose of the study was to evaluate the quality of Toki-shakuyaku-san extract granules (TJ-23) using chemiluminescence (CL). A linear relationship was obtained between the log value of the CL of TJ-23 and the reaction temperature. An excellent correlation (r= 0.999) was found between the slope of this curve (ΔA) and the colour intensity due to the browning reaction occurring at the early stage of the Maillard reaction.     

Summer drought exposure,stand structure,and soil properties jointly control the growth of European beech along a steep precipitation gradient in northern Germany

Increasing exposure to climate warming-related drought and heat threatens forest vitality in many regions on earth, with the trees' vulnerability likely depending on local climatic aridity, recent climate trends, edaphic conditions, and the drought acclimatization and adaptation of populations. Studies exploring tree species' vulnerability to climate change often have a local focus or model the species' entire distribution range, which hampers the separation of climatic and edaphic drivers of drought and heat vulnerability. We compared recent radial growth trends and the sensitivity of growth to drought and heat in central populations of a widespread and naturally dominant tree species in Europe, European beech (Fagus sylvatica), at 30 forest sites across a steep precipitation gradient (500–850 mm year⁻¹) of short length to assess the species' adaptive potential. Size-standardized basal area increment remained more constant during the period of accelerated warming since the early 1980s in populations with >360 mm growing season precipitation (April–September), while growth trends were negative at sites with <360 mm. Climatic drought in June appeared as the most influential climatic factor affecting radial growth, with a stronger effect at drier sites. A decadal decrease in the climatic water balance of the summer was identified as the most important factor leading to growth decline, which is amplified by higher stem densities. Inter-annual growth variability has increased since the early 1980s, and variability is generally higher at drier and sandier sites. Similarly, within-population growth synchrony is higher at sandier sites and has increased with a decrease in the June climatic water balance. Our results caution against predicting the drought vulnerability of trees solely from climate projections, as soil properties emerged as an important modulating factor. We conclude that beech is facing recent growth decline at drier sites in the centre of its distribution range, driven by climate change-related climate aridification.