The reproductive biology and genetic diversity of Potamophila parviflora R. Br.

Potamophila parviflora, a wild relative ofdomestic rice, is endemic to the north-eastern river systemsof New South Wales, Australia. It is the only member of the genus,and is habitat specific. Several new sites were found, mostly in theUpper Clarence catchment. Florets of P.parviflora were found to be 86%female-only, while 14% contained mature malereproductive parts, which occurred more often in the middle sectionof the panicle. Pollen was found to be necessary for the developmentof mature fruits. RAPD data showed that there is very little geneticvariation between individual plants, or between differentpopulations. An embryological study showed several irregularities inmegasporogenesis and megagametogenesis. No tetrads were observed inmegasporogenesis and the ovule is vacuolate at the megaspore mothercell stage. Megagametogenesis proceeded rapidly, nuclei within theovule were sometimes not spherical and varied in size, and sometimesthe antipodal cells doubled in number with a corresponding halving insize of the nuclei. Chromosome number varied between 2n = 24and 2n = 25, between and within populations. These resultsindicate that P. parvifloracould be a diplosporous apomict of the Antennaria type, althoughfurther works are required to provide conclusive proof.     

Radar reflectivity of titan

The present understanding of the atmosphere and surface conditions on Saturn's largest moon, Titan, including the stability of methane, and an application of thermodynamics leads to a strong prediction of liquid hydrocarbons in an ethane-methane mixture on the surface. Such a surface would have nearly unique microwave reflection properties due to the low dielectric constant. Attempts were made to obtain reflections at a wavelength of 3.5 centimeters by means of a 70-meter antenna in California as the transmitter and the Very Large Array in New Mexico as the receiving instrument. Statistically significant echoes were obtained that show Titan is not covered with a deep, global ocean of ethane, as previously thought. The experiment yielded radar cross sections normalized by the Titan disk of 0.38 +/- 0.15, 0.78 +/- 0.15, and 0.25 +/- 0.15 on three consecutive nights during which the sub-Earth longitude on Titan moved 50 degrees. The result for the combined data for the entire experiment is 0.35 +/- 0.08. The cross sections are very high, most consistent with those of the Galilean satellites; no evidence of the putative liquid ethane was seen in the reflection data. A global ocean as shallow as about 200 meters would have exhibited reflectivities smaller by an order of magnitude, and below the detection limit of the experiment. The measured emissivity at similar wavelengths of about 0.9 is somewhat inconsistent with the high reflectivity.     

Radar images of Mars

Full disk images of Mars have been obtained with the use of the Very Large Array (VLA) to map the radar reflected flux density. The transmitter system was the 70-m antenna of the Deep Space Network at Goldstone, California. The surface of Mars was illuminated with continuous wave radiation at a wavelength of 3,5 cm. The reflected energy was mapped in individual 12-minute snapshots with the VLA in its largest configuration; fringe spacings as small as 67 km were obtained. The images reveal near-surface features including a region in the Tharsis volcano area, over 2000 km in east-west extent, that displayed no echo to the very low level of the radar system noise. The feature, called Stealth, is interpreted as a deposit of dust or ash with a density less than about 0.5 gram per cubic centimeter and free of rocks larger than 1 cm across. The deposit must be several meters thick and may be much deeper. The strongest reflecting geological feature was the south polar ice cap, which was reduced in size to the residual south polar ice cap at the season of observation. The cap image is interpreted as arising from nearly pure CO(2) or H(2)O ice with a small amount of martian dust (less than 2 percent by volume) and a depth greater than 2 to 5 m. Only one anomalous reflecting feature was identified outside of the Tharsis region, although the Elysium region was poorly sampled in this experiment and the north pole was not visible from Earth.     

Bioavailability of an organophosphorus pesticide,fenamiphos, sorbed on an organo clay

Hydrolysis of an insecticide/nematicide, fenamiphos [ethyl-3-methyl-4-(methylthio)phenyl-(1-methylethyl)phosphoramidate], immobilized through sorption by cetyltrimethylammonium-exchanged montmorillonite (CTMA-clay) by a soil bacterium, Brevibacterium sp., was examined. X-ray diffraction analysis, infrared spectra, and a negative electrophoretic mobility strongly indicated that fenamiphos was intercalated within the bacterially inaccessible interlayer spaces of CTMA-clay. The bacterium hydrolyzed, within 24 h, 82% of the fenamiphos sorbed by the CTMA-clay complex. There was a concomitant accumulation of hydrolysis product, fenamiphos phenol, in nearly stoichiometric amounts. During the same period, in abiotic (uninoculated) controls, 4.6% of the sorbed insecticide was released into the aqueous phase as compared to 6.0% of the sorbed fenamiphos in another abiotic control where activated carbon, a sink for desorbed fenamiphos, was present. Thus, within 24 h, the bacterium hydrolyzed 77% more fenamiphos sorbed by organo clay than the amounts desorbed in abiotic controls. Such rapid degradation of an intercalated pesticide by a bacterium has not been reported before. Evidence indicated that extracellular enzymes produced by the bacterium rapidly hydrolyzed the nondesorbable fenamiphos, even when the enzyme itself was sorbed. Fenamiphos strongly sorbed to an organo clay appears to be readily available for exceptionally rapid degradation by the bacterium.     

Characterization of interdigital glands in the Asian elephant (Elephas maximus).

In the Asian elephant, wetness akin to perspiration is commonly observed on the cuticles and interdigital areas of the feet; this observation has lead to speculation regarding the existence of an interdigital gland. Our goal was to search for interdigital glands and characterise them morphologically, histochemically, and immunohistochemically. Necropsy samples of interdigital areas from two Asian elephants were obtained. Multiple sections were fixed and processed routinely, then stained with hematoxylin/eosin and differential mucin stains. Immunohistochemistry was also performed for cytokeratins 8 and 10. Interdigital glands resembling human eccrine glands were detected deep within the reticular dermis. Histochemical staining indicated neutral mucopolysaccharides and nonsulphated acid mucopolysaccharides in glandular secretions, and the glandular epithelium also showed immunoreactivity to cytokeratins 8 and 10. Both the histochemical and immunohistochemical staining patterns are analogous to human eccrine structures. This study shows with certainty that Asian elephants possess sweat glands as they are defined histologically.