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Artículo de revist

Induction of PEP Carboxylase and Crassulacean Acid Metabolism by Gibberellic Acid in Mesembryanthemum crystallinum

The induction of Crassulacean acid metabolism in Mesembryanthemum crystallinum was investigated in response to foliar application of gibberellic acid (GA). After 5 weeks of treatment, GA-treated plants showed 1.7- to almost a 4-fold increase of phosphoenolpyruvate carboxylase (PEPcase) activity with a concomitant increase in acid metabolism when compared to control plants. Immunoblot analysis indicated an increase in the PEPcase protein similar to that of salt treatment while Rubisco did not show a similar rise. The results indicate that exogenously applied GA accelerates plant developmental expression of PEPcase and Crassulacean acid metabolism in M. crystallinum

Weak solutions to the continuous coagulation equation with multiple fragmentation

The existence of weak solutions to the continuous coagulation equation with multiple fragmentation is shown for a class of unbounded coagulation and fragmentation kernels, the fragmentation kernel having possibly a singularity at the origin. This result extends previous ones where either boundedness of the coagulation kernel or no singularity at the origin for the fragmentation kernel were assumed

Size matters for single-cell C4 photosynthesis in Bienertia

Bienertia cycloptera belongs to a diverse set of plants, recently discovered to perform C4 photosynthesis within individual mesophyll cells. How these plants accomplish high photosynthetic efficiency without adopting Kranz anatomy remains unanswered. By modelling the processes of diffusion, capture, and release of carbon dioxide and oxygen inside a typical Bienertia mesophyll cell geometry, we show that a spatial separation as low as 10 μm between the primary and the secondary carboxylases, can, on its own, provide enough diffusive resistance to sustain a viable C4 pathway at 20 °C, with a CO2 leakage <35%. This critical separation corresponds to a cell diameter of 50 μm, consistent with the observed range where Bienertia’s mesophyll cells start to develop their characteristic mature anatomy. Our results are robust to significant alterations in model assumptions and environmental conditions, their applicability extending even to aquatic plants

Digital Surface Modelling in Developing Countries Using Spaceborne SAR Techniques

Topographic databases at the national level, in the form of Digital Surface Models (DSMs), are required for a large number of applications which have been spurred on by the increased use of Geographic Information Systems (GIS). Ground-Based (surveying, GPS, etc.) and traditional airborne approaches to generating topographic information are proving to be time consuming and costly for applications in developing countries. Where these countries are located in the tropical zone, they are affected by the additional problem of cloud cover which could cause delays for almost 75% of the year in obtaining optical imagery. The Caribbean happens to be one such affected territory that is in need of national digital topographic information for its GIS database developments, 3D visualization of landscapes and for use in the digital ortho-rectification of satellite imagery. The use of Synthetic Aperture Radar (SAR), with its cloud penetrating and day/night imaging capabilities, is emerging as a possible remote sensing tool for use in cloud affected territories. There has been success with airborne single-pass dual antennae systems (e.g. STAR 3i) and the Shuttle Radar Topographic Mapping (SRTM) mission. However, the use of these systems in the Caribbean are restrictive and datasets will not be generally available. The launching of imaging radar satellites such as ERS-1, ERS-2, Radarsat-1 and more recently Envisat have provided additional opportunities for augmenting the technologies available for generating medium accuracy, low cost, topographic information for developing countries by using the techniques of Radargrammetry (StereoSAR) and Interferometric SAR (InSAR). The primary aim of this research was to develop, from scratch, a prototype StereoSAR system based on automatic stereo matching and space intersection algorithms to generate medium accuracy, low cost DSMs, using various influencing parameters without any recourse to ground control points. The result was to be a software package to undertake this process for implementation on a personal computer. The DSMs generated from Radarsat-1 and Envisat SAR imagery were compared with a reference surface from airborne InSAR and conclusions with respect to the quality of the StereoSAR DSMs are presented. Work required to further improve the StereoSAR system is also suggested

First hollow stem: A critical wheat growth stage for dual-purpose producers

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Can High-risk Older Drivers be Identified in a DMV Setting with a Brief Battery of Functional Tests?

Recent research has indicated that some laboratory measures of functional ability may discriminate between crash-involved and crash-free older adults. However, the ability of these tests to provide the same level of discriminability in a real-world setting such as a Department of Motor Vehicles remains to be established. Therefore, in conjunction with the Maryland Department of Motor Vehicles and the National Highway Traffic Safety Administration, a brief battery of tests was developed and evaluated. The battery contained a number of cognitive tests (e.g., UFOV® subtest 2, the closure subtest of the Motor Free Visual Perception Test [MVPT], Trails A and B, etc.) and physical measures (e.g., Rapid Pace Walk, Head and Neck Rotation, etc.) that prior literature had indicated might be related to crash risk in older adults. Motor Vehicle Administration staff were trained to administer the test battery. Older adults (N=4,173, mean age =69 years) were approached by the staff after license renewal and asked to help evaluate the brief battery. Of the 4,173 older adults approached at the field sites, 2,112 individuals aged 55-96 years of age participated. The primary outcome of interest for this study was the occurrence of an at-fault Motor Vehicle Collision (MVC) following assessment. For members of this sample, the outcome period ranged from 2-3 years. Rate Ratios were determined for each functional variable based upon at-fault crashes adjusted for driving exposure over this period. Univariate analyses revealed that five variables (Age, Walk Time, MVPT, Trails A and UFOV®) were significantly related to crash frequency. These significant variables overlapped with one another to a certain degree, indicating that impaired older drivers score poorly on multiple cognitive assessments. The UFOV® subtest 2 appears to be the most strongly associated within this analysis (RR=3.78, p\u3c .05) and Rapid Pace Walk (RR=1.96, p \u3c .05) remained uniquely related to the frequency of state-reported, at-fault crashes. The role of such a screening battery in field settings such as a DMV will be discussed

Shaping and enforcing coordination spheres: probing the ability of tripodal ligands to favour trigonal prismatic geometry

The coordination chemistry of mono(2,2′-bipyrid-6-yl)bis(2-pyridyl)methanol (L1) and bis(2,2′-bipyrid-6-yl)mono(2-pyridyl)methanol (L2) are contrasted to tris(2,2′-bipyrid-6-yl)methanol (L3).L1andL2can produce octahedral complexes compared to the trigonal prismatic preference ofL3.</p