剌槐种子萌发过程的微量热法研究

用微量热法测定了剌槐种子的萌发热谱，发现其产热规律与其吸水规律和呼吸规律相关，并获得了衡量种子活力４个参数。     

Methods for the investigation of metabolic activities and shifts in the microbial community in a soil treated with a fungicide

Samples from a sandy agricultural soil were treated with increasing amounts of a fungicide (Sportak). The effects on the soil microflora were investigated over several weeks by monitoring basal and substrate-induced respiration and basal and substrate-induced heat output. The microbial biomass, metabolic quotient (qCO₂), relative heat output (rqheat), lag phase of substrate use, and calorimetric: respirometric ratio were used as ecophysiological parametèrs. As structural and community-specific parameters, we recorded tryptophan contents and auxin metabolism, and calculated the ratios of fungal to bacterial respiration by antibiotic inhibition of substrate-induced respiration. Sportak either inhibited or stimulated the microbiota, depending on the length of exposure to the fungicide and the amount applied. Mineralization of dead biomass was reflected in increased soil tryptophan contents after the Sportak application. A shortened lag phase demonstrated inhibition and a prolonged lag phase stimulation of substrate use. This changed with the experimental phase. The rqheat and the calorimetric: respirometric ratio proved to be suitable parameters for the detection of stress metabolism (repair processes) in soil microbiota, because thermodynamic processes and catabolic and anabolic metabolism are taken into account at the same time. Following the application of Sportak, indole 3-acetic acid biosynthesis decreased while indole-3-ethanol biosynthesis increased, probably as a result of a transitional community shift from K-strategists towards r-strategists. It was not the fungicide but the formulation (mainly xylol) that damaged the organisms. A shift in the ratio of fungi to bacteria was also observed, suggesting that the bacteria were probably more sensitive to xylol than the fungi.     

微量热法在土壤微生物研究中的应用进展

一切生命过程都伴随着热效应。微量热法可对这些热效应进行精确的跟踪,并表征其过程。微量热法已广泛应用于医药、生化等研究领域,但在土壤微生物研究中却鲜有应用。本文简要介绍微量热法的原理和实验方法,综述其在土壤微生物研究中的应用现状并展望其应用前景,以期为土壤微生物研究提供新的思路和技术。     

种子萌发热功率—时间曲线的测定及热动力学研究

用自研制的热导式微热量计测定了8902s、珍汕97雄性不育稻种和刺槐树种萌发热功率-时间曲线。种子萌发热功率-时间曲线呈现浸透、活化和生长生理三阶段。用动力学方法计算了种子萌发生长速率常数（K）、生长限制因子（S）、衰减速率常数（β）以及种子萌发生长物质单位增长量的热功率（Po），并建立了相应的种子萌发生长热动力学经验式。     

Pattern of microbial indicators in forest soils along an European transect

Microbial biomass C and activity were determined in six forest soils along a gradient in physical and chemical climate in Europe. Both parameters were measured microcalorimetrically. The upper 22 cm of the soils were sampled in undisturbed columns (24 cm deep). Measurements were made in homogenized samples of the different surface organic horizons (Ol, Of, Oh) and the mineral horizons (Ah, Aeh, Bv) down to 22 cm.On a mass basis values for both the biomass and the activity showed an exponential decrease with depth in all soils. Expressed on a volume basis these relationships varied with soil pH. in the strongly acidified soils most of the microbial biomass and activity was located in the forest floor. In less acidified soils both parameters were highest in the mineral soil.Further relationships between biomass and activity and between soil chemical properties showed significant positive correlations with exchangeable Ca²⁺, Mg²⁺, Ca/Al and negative correlations with Al³⁺. There were no significant correlations with exchangeable cations in less acidified soils. It was calculated that the microbial biomass is more affected by soil chemistry than activity. The caloric quotient (qW) is a good parameter for determining the ecophysiological state of microorganisms in acidified soils.     

Microcalorimetric evaluation of soil microbiological properties under plant residues and dogmatic water gradients in Red soil

A study of 6 months duration was carried out to investigate the effect of water regimes and organic amendments on the soil microbial biomass and microbial population under Red soil collected from Hunan Providence, China. The soil microbial biomass and population were measured with traditional methods and results obtained by conventional methods, corroborated with microcalorimetry. The incorporation of rice (Oryza sativa L.) straw (RS) and green manure (GM), especially at high rates, enhanced the soil microbial activities. We observed that the use of GM exhibited more significant stimulating effects on microbial activities than RS. Similarly, water regimes, 25% (W1) and 200% (W2) of water holding capacity, also had significant effects on microbial activities. Comparing the effects of water levels, we noticed that W2 had a significant negative influence on soil microbial biomass and population. To compare the results of conventional methods and to check the sensitivity of microcalorimetry, the thermodynamic parameters, microbial growth rate constant (k), total heat evolution (Q), peak height (P_max) and peak time (t_max) were calculated. Highest P_max, k and Q were observed in GM treatments at water regime W1, while highest t_max values were recorded in CK (control) and RS treatments at W2. The microcalorimetric parameters, P_max, k and Q were positively correlated, whereas t_max negatively linked with microbial biomass and population at p < 0.01. Our results suggest that microcalorimetry successfully verified the results obtained from customary methods and microcalorimetric parameters P_max, t_max, Q and k proved that they are highly sensitive to microbial properties and could be used as indices of microbial community shifts and activities in soil ecosystems.     

Soil microbial activity measured by microcalorimetry in response to long-term fertilization regimes and available phosphorous on heat evolution

Microcalorimetric technique was used to investigate the effects of balanced versus nutrient-deficiency fertilization on soil microbial activity in a long-term (19-year) fertilizer experiment. The number of microorganisms in soils was measured by viable cell count, and the power-time curves were recorded for soil samples supplemented with glucose and ammonium sulphate, also with or without sodium dihydrogen phosphate for P-deficiency fertilization. Both the bacterial and the fungal populations were significantly higher (P < 0.05) under balanced fertilization than under nutrient-deficiency fertilization. The microbial activity presented by heat dissipation per cell unit indicated that microorganisms under balanced fertilizer treatments had more efficient metabolism, while decreased microbial activity under nutrient-deficiency treatments was firstly due to soil available P, followed by N and K (P < 0.05). In addition, microbial growth in soils under P-deficiency fertilization was stimulated by adding available P, while the lower growth rate, less peak heat, and longer peak time all indicated the low activity of soil microorganisms. We emphasize the importance of balanced fertilization, as well as the role of available P, in maintaining and promoting soil microbial activity.     

Microcalorimetric study of changes in the microbial activity in a humic Cambisol after reforestation with eucalyptus in Galicia (NW Spain)

The microcalorimetric technique was used to analyse the influence of successive reforestations with Eucalyptus globulus Labill, a fast growing species, on the microbial activity in soil. With this aim, samples of similar origin soils, humic-eutrophic Cambisol, were collected from two adjacent land plots. One of the plots, to be taken as the reference, was not subjected to man activities for the last 100 years. The other plot was subjected to two reforestations in the last 20 years. For collection of the two samples, 100 m² homogeneous and perfectly defined zones were chosen in each of the adjacent land plots to obtain final representative bulk samples of 400 g each.The study was carried out using the microbial population as a bioindicator of the productive potential in soil. The experiments were carried out using 1 g soil samples that were treated with 1.25 mg glucose and stored at 4 °C for 3 months. The analysis was complemented by the determination of physical, chemical, and biological properties and environmental parameters.The study was performed over 1 year and samples were seasonally collected (spring, summer, autumn and winter) in the same zone situated in Viveiro (Galicia, NW Spain) with the objective of checking the influence of environmental conditions on the microbial activity in the two soils studied.From the measured results, it can be observed that soils subjected to reforestations suffer not only important changes in physical structure, such as an increase in bulk density, from 600 to 660 kg m⁻³, a reduction in hydraulic conductivity, from 8.85×10⁻³ to 4.4×10⁻³ m s⁻¹, or a decrease in the C-to-N ratio, from 13 to 8, but also they have lower microbial activity, for example 2.84 J g⁻¹ in the reforested soil versus 6.14 J g⁻¹ in the reference soil, in spring, thus presenting a lower productive potential that suggests the use of both amendments and adequate management techniques to ensure a sustainable exploitation, thus avoiding future degradation of soil.     

微量热技术在生命科学及秸秆降解腐熟研究中的应用

综述了微量热技术的特点、工作原理以及其在生命科学中的应用和进展,并重点阐述了其在秸秆降解腐熟中的应用。