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1.
Modelling crop growth and biomass partitioning to shoots and roots in relation to nitrogen and water availability,using a maximization principle 总被引:1,自引:0,他引:1
Many crop models relate the allocation of dry matter between shoots and roots exclusively to the crop development stage. Such models may not take into account the effects of changes in environment on allocation, unless the allocation parameters are altered. In this paper a crop model with a dynamic allocation parameter for dry matter between shoots and roots is described. The basis of the model is that a plant allocates dry matter such that its growth is maximized. Consequently, the demand and supply of carbon, nitrogen, and water is maintained in balance. This model supports the hypothesis that a functional equilibrium exists between shoots and roots.This paper explains the mathematical computation procedure of the crop model. Moreover, an analysis was made of the ability of a crop model to simulate plant dry matter production and allocation of dry matter between plant organs. The model was tested using data from a greenhouse experiment in which spring wheat (Triticum aestivum L.) was grown under different soil moisture and nitrogen (N) levels.Generally, the model simulations agreed well with data recorded for total plant dry matter. For validation data the coefficient of determination (r2) between simulated and measured shoot dry weight was 0.96. For the validation treatments r2 was slightly lower, 0.94. In addition to dry matter production the model succeeded satisfactorily in simulating the dry weight of different plant organs. The response of simulated root to shoot ratio to the level of soil moisture was mainly in accordance with the measured data. In contrast, the simulated ratio seemed to be insensitive to the changes in the levels soil N concentration used in the experiment.The data used in the present study were not extensive, and more data are needed to validate the model. However, the results showed that the model responses to the changes in soil N and water level were realistic and mostly agreed with the data. Thus, we suggest that the model and the method employed to allocate dry matter between roots and shoots are useful when modelling the growth of crops under N and water limited conditions. 相似文献
2.
Summary The CO2 exchange of the Empetrum nigrum-Sphagnum fuscum community of a raised bog was studied in the laboratory at different temperature (from 5 to 30° C) and irradiance (up to 128 W m-2) combinations during one growing season. The total CO2 exchange was divided into three components, namely those due to Empetrum nigrum, Sphagnum fuscum, and peat, respectively. At the optimum temperature (10 to 15° C) the maximum net CO2 exchange of Empetrum nigrum was c. 200 and that of Sphagnum fuscum c. 250 mg CO2 m-2h-1. The total respiration in peat increased exponentially from 50 to 350 mg CO2 m-2h-1 with increasing temperature from 5 to 30° C. About 40% of the CO2 fixed by the community in optimal temperature and irradiation conditions was released immediately. 相似文献
3.
The estimation of parameters in several dynamic models, which describe growth and substrate consumption, has been carried out using a modified Gauss-Newton-type method. The four models considered are Monod, Contois, linear specific growth rate, and an enzyme kinetic model. The initial values of the differential equations are included in the parameter vector which will be estimated. The efficiency of the method and the confidence limits of the parameters were studied using simulated measurement noise. The experimental results describe Trichoderma viride growing on glucose as the main carbon source. 相似文献
4.
5.
Juha Karjalainen Olli Urpanen Tapio Keskinen Hannu Huuskonen Jouko Sarvala Pentti Valkeajrvi Timo J. Marjomki 《Ecology and evolution》2016,6(3):779-790
Fish are known for their high phenotypic plasticity in life‐history traits in relation to environmental variability, and this is particularly pronounced among salmonids in the Northern Hemisphere. Resource limitation leads to trade‐offs in phenotypic plasticity between life‐history traits related to the reproduction, growth, and survival of individual fish, which have consequences for the age and size distributions of populations, as well as their dynamics and productivity. We studied the effect of plasticity in growth and fecundity of vendace females on their reproductive traits using a series of long‐term incubation experiments. The wild parental fish originated from four separate populations with markedly different densities, and hence naturally induced differences in their growth and fecundity. The energy allocation to somatic tissues and eggs prior to spawning served as a proxy for total resource availability to individual females, and its effects on offspring survival and growth were analyzed. Vendace females allocated a rather constant proportion of available energy to eggs (per body mass) despite different growth patterns depending on the total resources in the different lakes; investment into eggs thus dictated the share remaining for growth. The energy allocation to eggs per mass was higher in young than in old spawners and the egg size and the relative fecundity differed between them: Young females produced more and smaller eggs and larvae than old spawners. In contrast to earlier observations of salmonids, a shortage of maternal food resources did not increase offspring size and survival. Vendace females in sparse populations with ample resources and high growth produced larger eggs and larvae. Vendace accommodate strong population fluctuations by their high plasticity in growth and fecundity, which affect their offspring size and consequently their recruitment and productivity, and account for their persistence and resilience in the face of high fishing mortality. 相似文献
6.
A polyamine analogue prevents acute pancreatitis and restores early liver regeneration in transgenic rats with activated polyamine catabolism 总被引:4,自引:0,他引:4
Rasanen TL Alhonen L Sinervirta R Keinanen T Herzig KH Suppola S Khomutov AR Vepsalainen J Janne J 《The Journal of biological chemistry》2002,277(42):39867-39872
We recently generated a transgenic rat model for acute pancreatitis, which was apparently caused by a massive depletion of pancreatic polyamines spermidine and spermine due to inducible activation of their catabolism (Alhonen, L., Parkkinen, J. J., Kein?nen, T., Sinervirta, R., Herzig, K. H., and J?nne, J. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 8290-8295). When subjected to partial hepatectomy, these animals showed striking activation of polyamine catabolism at 24 h postoperatively with a profound decrease in hepatic spermidine and spermine pools and failure to initiate liver regeneration. Here we show that pancreatitis in this model could be totally prevented, as judged by histopathology and plasma alpha-amylase activity, by administration of 1-methylspermidine, a metabolically stable analogue of spermidine. Similarly, the analogue, given prior to partial hepatectomy, restored early liver regeneration in the transgenic rats, as indicated by a dramatic increase in the number of proliferating cell nuclear antigen-positive hepatocytes from about 1% to more than 40% in response to the drug. The present results suggest that the extremely high concentration of spermidine in the pancreas, in fact the highest in the mammalian body, may have a critical role in maintaining organ integrity. The failure to initiate liver regeneration in the absence of sufficient hepatic polyamine pools similarly indicates that polyamines are required for proper commencement of the regenerative process. 相似文献
7.
An instrumentation and automation system for a side-vented pan coater with a novel air-flow rate measurement system for monitoring
the film-coating process of tablets was designed and tested. The instrumented coating system was tested and validated by film-coating
over 20 pilot-scale batches of tablets with aqueous-based hydroxypropyl methylcellulose (HPMC). Thirteen different process
parameters were continuously measured and monitored, and the most significant ones were logged for analysis. Laser profilometry
was used to measure the surface roughness of the coated tablets. The instrumentation system provided comprehensive and quantitative
information on the process parameters monitored. The measured process parameters and the responses of the film-coated tablet
batches showed that the coating process is reproducible. The inlet air-flow rate influenced the coating process and the subsequent
quality of the coated tablets. Increasing the inlet flow rate accelerated the drying of the tablet surface. At high inlet
flow rate, obvious film-coating defects (ie, unacceptable surface roughness of the coated tablets) were observed and the loss
of coating material increased. The instrumented and automated pancoating system described, including historical data storage
capability and a novel air-flow measurement system, is a useful tool for controlling and characterizing the tablet film-coating
process. Monitoring of critical process parameters increases the overall coating process efficiency and predictability. 相似文献
8.
- 1 In order to study the dynamics of primary production and decomposition in the lake littoral, an interface zone between the pelagial, the catchment and the atmosphere, we measured ecosystem/atmosphere carbon dioxide (CO2) exchange in the littoral zone of an eutrophic boreal lake in Finland during two open water periods (1998–1999). We reconstructed the seasonal net CO2 exchange and identified the key factors controlling CO2 dynamics. The seasonal net ecosystem exchange (NEE) was related to the amount of carbon accumulated in plant biomass.
- 2 In the continuously inundated zones, spatial and temporal variation in the density of aerial shoots controlled CO2 fluxes, but seasonal net exchange was in most cases close to zero. The lower flooded zone had a net CO2 uptake of 1.8–6.2 mol m?2 per open water period, but the upper flooded zone with the highest photosynthetic capacity and above‐ground plant biomass, had a net CO2 loss of 1.1–7.1 mol m?2 per open water period as a result of the high respiration rate. The excess of respiration can be explained by decomposition of organic matter produced on site in previous years or leached from the catchment.
- 3 Our results from the two study years suggest that changes in phenology and water level were the prime cause of the large interannual difference in NEE in the littoral zone. Thus, the littoral is a dynamic buffer and source for the load of allochthonous and autochthonous carbon to small lakes.
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10.
Nutrient concentration in shape Sphagna at increased N-deposition rates and raised atmospheric CO2 concentrations 总被引:1,自引:0,他引:1
Sphagnum fuscum, S. magellanicum, S. angustifolium and S. warnstorfii were treated with N deposition rates (0, 10, 30 and 100 kg ha-1 a-1) and with four atmospheric CO2 concentrations (350, 700, 1000 and 2000 ppm) in greenhouse for 71–120 days. Thereafter, concentrations of total N, P, K, Ca and Mg in the capitulae of the Sphagna were determined. The response of each species to N deposition was related to ecological differences. With increasing N deposition treatments, moss N concentrations increased and higher N:P-ratios were found, the increase being especially clear at the highest N load. Sphagnum fuscum, which occupies ombrotrophic habitats, was the most affected by the increased nitrogen load and as a consequence the other elements were decreased. Oligotrophic S. magellanicum, wide nutrient status tolerant S. angustifolium and meso-eutrophic S. warnstorfii tolerated better increased N deposition, though there were increased concentrations of Ca and Mg in S. warnstorfii and Mg in S. magellanicum. Nitrogen and P concentrations decreased with raised CO2 concentrations, except for S. magellanicum. This seems to be the first time this kind of response in nutrient concentrations to enhanced CO2 concentration has been shown to exist in bryophytes. The concentration of K clearly decreased in S. fuscum as did the concentration of Mg in the other Sphagna with increasing CO2. Sphagnum angustifolium and S. magellanicum, which are the less specialized species, were the least affected by the CO2 treatments. 相似文献