John S. Gardner

Identifying inflorescence phytoliths from selected species of wheat (Triticum monococcum, T. dicoccon, T. dicoccoides, and T. aestivum) and barley (Hordeum vulgare and H. spontaneum) (Gramineae)

Analysis of microfossil silica phytoliths is becoming an increasingly important research tool for taxonomists, archaeobotanists, and paleoecologists. Expanded use of phytolith analysis by researchers is dependent upon development of phytolith systematics. In this study phytoliths produced by the inflorescence bracts from four species of wheat, Triticum monoccocum, T. dicoccon, T. dicoccoides, and T. aestivum, and two species of barley, Hordeum vulgare, and H. spontaneum, were analyzed using computer-assisted image and statistical analysis with the intent to develop taxonomic tools to distinguish among the taxa. A classification key based on significant differences among the mean morphometries of the inflorescence phytoliths produced by each species was created and tested. Discriminant analysis of the morphometries of several morphotypes of phytoliths was also conducted to determine whether this computer-assisted statistical procedure could be used as another method to classify the taxa and to determine which morphotypes have measurements that can best be used in discriminant functions. Test results indicated that, at the genus level, both the classification key and discriminant analysis of certain morphotypes of phytoliths were relatively reliable tools for distinguishing among phytoliths produced in the inflorescence bracts of the taxa considered. For distinguishing among the taxa at the species level, the classification key was most reliable. Of the discriminant analyses tested, that based on all the phytolith morphotypes combined was more reliable than those based on only one morphotype.

Study of natural photonic crystals in beetle scales and their conversion into inorganic structures via a sol–gel bio-templating route

The origin of the structural colors from several different examples of the weevil and longhorn families (Curculionidae and Cerambycidae, respectively) was investigated by structural and optical characterization techniques. A range of interesting three-dimensional photonic crystal structures operating at visible wavelengths was discovered, including both disordered and ordered non-close-packed lattices of cuticular spheres and bicontinuous diamond-based architectures. The discovered photonic structures display a large variation in lattice constants and dielectric filling fractions and thereby create optical reflectance colors spanning the entire visible range. To transform these bio-polymeric photonic crystals into heat and photo-stable inorganic structures, a low-temperature bio-templating method was developed. Using organic–inorganic hybrid silica sol–gel infiltration–templation chemistry combined with acid-etching template removal, stable inverse photonic structures were fabricated. The inverse structures display good structural quality and vivid reflection properties.

Analysis of lichen thin sections by PIXE and STIM using a proton microprobe

Abstract In order to better understand the distribution pattern of mineral elements in lichen tissues, thin sections (15 μm) of the foliose, vagrant soil lichen Xanthoparmelia chlorochroa were examined using proton microprobe Particle induced X-ray emission (PIXE). This technique was used to make two-dimensional scans, with 5 μm resolution, across tissue cross sections of the test species. Element maps for Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, and As have been prepared. Several elements are strongly localized in the element maps. PIXE data are complimented with STIM, light micrographs, and SEM images. Preliminary data suggest that nuclear microprobe techniques may be useful in elucidating element absorption and transport mechanisms in lichens.

Pseudoscopic illusions in stereo views of freeze-etch replicas

SummaryThe use of stereo pairs of freeze-etch replicas significantly contributes to the interpretation of spatial relationships of structures within fungal spores. However, great care must be taken to assure proper orientation of prints before publication in order to prevent pseudoscopic illusions (an optical illusion which produces an apparent reversal of surface elevations and depressions). AsHarold C. Conklin [2] pointed out in his letter to Science, this phenomenon is an ever present concern for users of vertical imagery. The sensation of seeing depth in two dimensional photographs is an illusion. The goal is to create the proper illusion.In order to convey the desired information to the reader it is essential that surface photographs be oriented as if the illumination were coming mostly from the top of the page and the shadows were projected toward the bottom of the page. Examples of neglecting this simple rule may be found in publications ranging from news magazines [5] to prestigeous scientific journals [3, 4]. Articles occasionally contain photographs which are rotated 180 degrees from the proper orientation and thus convex surfaces are displayed as concave surfaces and vice versa. In stereo pairs of electron micrographs of freeze-etch replicas pseudoscopic illusions are also caused by transposing the right hand micrograph with the left hand micrograph. When viewed in the proper orientation the various organelle spatial relationships and membrane surfaces, and other structures, are clearly discernable and easily understood. However when the same micrographs are transposed from left to right, entirely erroneous concepts are conveyed. For example protoplasmic surfaces appear as exoplasmic surfaces [1]. An organelle whose image is actually present will vanish leaving behind only its imprint.

Lichen Biodeterioration at Inscription Rock, El Morro National Monument, Ramah, New Mexico, USA

El Mono National Monument is located in Cibola County, New Mexico, about 200 km west of Albuquerque, New Mexico. The main attraction at the Monument is Inscription Rock, a large sandstone formation which has become a natural repository for more than 700 years of comments and notations recorded by travelers through the region. Recently, encroachment of lichens onto several inscription panels has been documented. Because lichens are known to decompose rock surfaces physically and chemically, lichen communities on several panels have been studied. Species and relative abundance data have been compiled. Distribution of lichen species on each panel has been photographically documented in order to monitor future growth/encroachment trends, exfoliation patterns, and changes in species composition. Samples of common lichen species on the Inscription Rock panels were collected from a large, separate boulder field north of the Rock. These samples have been analyzed using thin-layer chromatography and SEM and light microscopy. PIXE analysis was also performed on Usnea hirta samples from five locations in the Monument to determine if air pollution is influencing substrate degradation patterns. Since establishment of the Monument, protection from grazing and wood cutting/gathering has resulted in changes in the microenvironment in and around several of the panels. SEM and light microscopy analysis have shown that mycobiont hyphae regularly penetrate up to 20mm into rock surfaces. TLC analysis has shown that virtually all the major lichen species on the panels produce at least 4–5 secondary chemicals including several organic acids. Elemental analysis data from Usnea hirta samples confirm that all potential pollutant elements are well within background levels. Preemptive recommendations include: 1) continue to monitor growth plots; 2) set up biocide studies; and 3) selectively remove the woody vegetation adjacent to some panels.

Stomatal Characterization of Grass Leaves by Four Preparation Techniques

Four leaf preparation techniques (air drying, tetramethylsilane air drying, critical point drying, and freeze substitution) used in scanning electron microscopy (SEM) were evaluated with respect to the degree of cellular distortion they produce in stomatal guard cells of leaves of Dactylis glomerata and Elymus canadensis . Surface morphological distortion and cuticle disruption in the air-dried and tetramethylsilane air-dried leaves, and cuticle disruption within the critical point-dried tissue made it difficult to obtain measurements.The freeze-substituted tissue experienced little cuticle disturbance, and the cellular morphology appeared normal. The length of the guard cells did not significantly differ between the air-dried, tetramethylsilane air-dried, critical point-dried, or freeze-substituted samples. Widths did significantly vary, with the freeze-substituted tissue having lower values than tissues treated with the other treatments. Freeze substitution methodology produced SEM images that appear to be less distorted and allow easy and precise measurement.