Does a gender of Welwitschia mirabilis plants influence their photosynthetic activity?

Welwitschia mirabilis Hook.f. (Welwitschiaceae, Gnetales) is a gymnosperm plant unique in its habit with an isolated taxonomic position. This species is dioecious, but no studies of its photosynthetic activity were conducted with examination of differences among male and female plants. To fill this gap, the day and night photosynthetic activity of male and female specimens of Welwitschia mirabilis cultivated in the botanical garden was studied in controlled conditions. Photosynthetic activity was studied using net photosynthetic rate (PN), stomatal conductance (gs) and intercellular CO2 concentration (Ci) parameters. Additionally, a normalized difference vegetation index (NDVI) was used to assess the condition among male and female plants in full sunlight. The studied Welwitschia plants revealed variability in photosynthetic activity both during the day and the night. The photosynthetic activity was low in the morning hours and higher in the afternoon. There is a difference in the photosynthetic activity during the night between sexes, being higher in female specimens. Stomatal density was evaluated separately for adaxial and abaxial leaf surfaces. Statistically significant differences in the stomatal density on abaxial and adaxial leaf surfaces were observed in both sexes, especially distinctive in female specimens. NDVI has revealed that there were weak differences between male and female plants.

Verification of Geometric Model-Based Plant Phenotyping Methods for Studies of Xerophytic Plants.

This paper presents the results of verification of certain non-contact measurement methods of plant scanning to estimate morphological parameters such as length, width, area, volume of leaves and/or stems on the basis of computer models. The best results in reproducing the shape of scanned objects up to 50 cm in height were obtained with the structured-light DAVID Laserscanner. The optimal triangle mesh resolution for scanned surfaces was determined with the measurement error taken into account. The research suggests that measuring morphological parameters from computer models can supplement or even replace phenotyping with classic methods. Calculating precise values of area and volume makes determination of the S/V (surface/volume) ratio for cacti and other succulents possible, whereas for classic methods the result is an approximation only. In addition, the possibility of scanning and measuring plant species which differ in morphology was investigated.

Surface modeling--uncertainty estimation and visualization.

The work presents a method of determining uncertainty of surface-based models that are reconstructed fragments of a human body built on the basis of slice images received from computed tomography CT or magnetic resonance imaging MRI. An analysis of geometric structure of the models has been carried out determining features, such as local inclination angle of the normal to the surface relative to the direction of scanning, and local radius of curvature. These features, together with the distance between slice images, have the largest influence on accuracy of the reconstructed surface-based models. A model of uncertainty has been determined by comparing properly selected virtual anatomical models and their spatial reconstructions. The estimated uncertainty model has then been employed to determine local errors in geometric structure of surface-based models. A quality visualisation of the errors in the geometric model has been presented in the form of a colour scale, and a quantity visualisation in the form of a ribbon, whose width is proportional to the uncertainty model.

An attempt to use Computer Assisted Orthopedic Surgery in the diagnosis and treatment of hip deformations.

Background. Computer Assisted Orthopaedic Surgery (CAOS) enables complex 3D planning of surgery and the precise navigation of surgical instruments or implants during the operation. This procedure may also be helpful in preparing pelvic osteotomies, by enabling a pre-operative, virtual assessment of the results of the surgery. The purpose of this paper is to present the possibilities of our "Super Pelvis" software in assisting the diagnostics and treatment of diseases of the hip. Material and methods. We have developed a soft-ware program called "Super Pelvis," which enables 3D reconstruction of any part of the skeleton based on CT scans. It also enables 3D qualitative assessment of the whole pelvis by rotation and magnification. The material consisted of 30 dry, healthy adult skeletons gained from a medieval cemetery. In every pelvis both acetabuli were examined three times to measure the modified center-edge angles (CEA) and the anterior and posterior sector angles. The first step was a morphologic examination based on two photographs taken in frontal and transverse view. X-rays were also taken in the same views as the photographs to assess the same parameters. Then these same parameters were measured using "Super Pelvis." Results and Conclusions. All three methods of measurement have high reproducibility and there is statistically significant correlation between them. The "Super Pelvis" soft-ware seems to be useful in the precise measurement of parameters describing the acetabulum. This is the first step in creating a software package for intra-operative navigation in pelvic surgery.

The application of computer assistance in planning osteotomy of the proximal femur.

Background. The aim of this article is to demonstrate the capabilities of the SCFEanalyzer computer program, which may be helpful in preoperative planning of osteotomy of the proximal femur. Material and methods. Computed tomography scans were performed on human bone specimens: one pelvis and two femoral bones (right and left). The CT data were used to demonstrate the abilities of our SCFEanalyzer software, which utilizes three-dimensional virtual models of anatomic structures constructed from these data. The software enables qualitative and quantitative spatial analysis of chosen parameters analogous to those done on the basis of plain radiographs. SCFEanalyzer makes it possible to evaluate the function of the hip joint by calculating the range of motion depending on the shape of bone structures. On the basis of the analysis of femoral geometry and function of the hip joint, it is possible to plan and simulate osteotomy of the proximal femur on the computer screen. Analogous qualitative and quantitative evaluation after performing the virtual surgery enables its potential effects to be assessed. Conclusions. The use of computer assistance in preoperative planning enable us to increase objectivity and repeatability, and to compare the results of different types of osteotomy of the proximal femur, and thus to choose the optimal operation in each individual case.