Modelling crop growth and biomass partitioning to shoots and roots in relation to nitrogen and water availability,using a maximization principle

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.     

Thermostable endoglucanases in the liquefaction of hydrothermally pretreated wheat straw

Background  

Thermostable enzymes have several benefits in lignocellulose processing. In particular, they potentially allow the use of increased substrate concentrations (because the substrate viscosity decreases as the temperature increases), resulting in improved product yields and reduced capital and processing costs. A short pre-hydrolysis step at an elevated temperature using thermostable enzymes aimed at rapid liquefaction of the feedstock is seen as an attractive way to overcome the technical problems (such as poor mixing and mass transfer properties) connected with high initial solid loadings in the lignocellulose to ethanol process.     

Evolution of the spectrin repeat

We now know that the evolution of multidomain proteins has frequently involved genetic duplication events. These, however, are sometimes difficult to trace because of low sequence similarity between duplicated segments. Spectrin, the major component of the membrane skeleton that provides elasticity to the cell, contains tandemly repeated sequences of 106 amino acid residues. The same repeats are also present in α-actinin, dystrophin and utrophin. Sequence alignments and phylogenetic trees of these domains allow us to interpret the evolutionary relationship between these proteins, concluding that spectrin evolved from α-actinin by an elongation process that included two duplications of a block of seven repeats. This analysis shows how a modular protein unit can be used in the evolution of large cytoskeletal structures.     

Detection of Plasmodium falciparum DNA in a microtitration plate-based hybridization test

A rapid DNA-test, depending on the affinity based hybrid collection principle, was developed for the detection of Plasmodium falciparum DNA from clinical specimens. In this method, hybridization takes place in solution and the hybrids are collected onto a solid phase for measurement. Two probes are used, one labelled with an affinity tag (biotin) and the other with a detectable label (32P). In the present test a single oligonucleotide complementary to a 21-base pair sequence which is highly repeated in the parasite genome served both as capture and detector probe. The test is a 2-h hybridization performed in streptavidin coated microtitration plate wells, onto which the labelled hybrids simultaneously bind. The sensitivity of the assay with a crude erythrocyte lysate specimen was 1.6 x 10(9) repeat units corresponding to about 160 parasites in one microliter blood. The results allowed quantification of the repeat sequences and thus estimation of the degree of parasitemia in clinical specimens.     

Fructose metabolism in Zymomonas mobilis

Summary In the metabolism of fructose by Zymomonas, the ethanol yield is decreased due to the formation of dihydroxyacetone, mannitol and glycerol. The reduction of fructose to mannitol by an NADPH-dependent mannitol dehydrogenase is apparently coupled to the oxidation of glucose-6-phosphate by glucose-6-phosphate dehydrogenase, which exhibits higher activity with NADP than with NAD as cofactor. The relatively low cell yield on fructose can partly be explained by the loss of ATP in the formation of dihydroxyacetone and glycerol and partly by the toxic effect of dihydroxyacetone and acetaldehyde on the growth of the organism.     

The influence of neuropeptide Y and norepinephrine on ovulation in the rat ovary.

Neuropeptide Y (NPY) was measured in tissue extracts from ovaries of rats treated with pregnant mare serum gonadotropin (PMSG). The extracted NPY-immunoreactive material was identical to synthetic human NPY with regard to size and hydrophobicity as evaluated by gel filtration and high performance liquid chromatography. The concentration of NPY was related to the estrous cycle and a maximum was observed in relation to the endogenous luteinizing hormone (LH) peak. NPY immunoreactivity was demonstrated by immunohistochemistry to be localized within nerve fibers supplying blood vessels and follicles. The increase in the NPY content could not be related to accumulation around specific ovarian structures. Employing an in vitro set-up, NPY (10(-7) M) was unable to induce ovulation and did not increase the ovulation rate in LH-stimulated ovaries. The combination of NPY (10(-7) M) and NE (10(-7) M) did not significantly increase the number of ovulations compared to that induced by NE (10(-7) M) alone. In conclusion, NPY content in the ovary is related to the estrous cycle, but NPY does not seem to have any direct effect on the ovulatory process.     

The induction of inflammation by dectin-1 in vivo is dependent on myeloid cell programming and the progression of phagocytosis

Dectin-1 is the archetypal signaling, non-Toll-like pattern recognition receptor that plays a protective role in immune defense to Candida albicans as the major leukocyte receptor for beta-glucans. Dectin-1-deficiency is associated with impaired recruitment of inflammatory leukocytes and inflammatory mediator production at the site of infection. In this study, we have used mice to define the mechanisms that regulate the dectin-1-mediated inflammatory responses. Myeloid cell activation by dectin-1 is controlled by inherent cellular programming, with distinct macrophage and dendritic cell populations responding differentially to the engagement of this receptor. The inflammatory response is further modulated by the progression of the phagocytosis, with "frustrated phagocytosis" resulting in dramatically augmented inflammatory responses. These studies demonstrate that dectin-1 in isolation is sufficient to drive a potent inflammatory response in a context-dependent manner. This has implications for the mechanism by which myeloid cells are activated during fungal infections and the processes involved in the therapeutic manipulation of the immune system via exogenous dectin-1 stimulation or blockade.     

The first metal complexes bearing ligated 3-iminoisoindolin-1-ones

The reaction between Zn(OAc)₂ · 2H₂O (1) and the 3-iminoisoindolin-1-ones H₂NCNC(O)C₆R¹R²R³R⁴ (R¹-R⁴ = H 2; R¹, R⁴ = H, R², R³ = Cl 3; R¹, R³, R⁴ = H, R² = Me 4) in EtCN at 70 °C for ca. 12 h affords the novel family of complexes [Zn{H₂NCNC(O)C₆R¹R²R³R⁴}₂(OAc)₂] (R¹-R⁴ = H 5; R¹, R⁴ = H, R², R³ = Cl 6; R¹, R³, R⁴ = H, R² = Me 7) in excellent (90% and 93% for 5 and 6, correspondingly) to good (64% for 7) yields. The isolated compounds were characterized by elemental analyses (C, H, N), IR, NMR and ESI⁺-MS. X-ray diffraction data for 2 and 5 indicate that both free (2) and ligated (5) 3-iminoisoindolin-1-ones exist in the zwitterionic form.