Structural changes in the innercortex cells of soybean root nodules are induced by short-term exposure to high salt or oxygen concentrations

After a 2 h exposure of intact soybean nodules to high concentrations of NaCl (100mol m_?3) or oxygen (8OkPa O₂), morphometric computations carried out using an image analysis technique on semi-thin sections showed that both treatments induced a decrease in the area of the inner-cortex cells, which were then characterized by a tangential elongation. In contrast, no significant change in area occurred in the middle-cortex cells although their elongation decreased. Electron microscopic observations showed that in the inner-cortex cells changes included the presence of wall infoldings, an enlarged periplasmic space and a lobate nucleus whose chromatin distribution differed from that of the control. Structural changes also occurred in the endoplasmic reticulum, microbodies, mitochondria and plastids. From several of these changes, which are similar to those noted in osmocontractil cells in response to external stimuli, it can be hypothesized that the inner cortex may provide a potential mechanism for the control of oxygen diffusion through the nodules.     

Change in the H2 photoproduction capability in a synchronously grown aerobic nitrogen-fixing cyanobacterium,Synechococcus sp. Miami BG 043511

Synchronously growing cells of nitrogen-fixing Synechococcus sp. Miami BG 043511 were harvested periodically and the capability for hydrogen photoproduction in closed vessels was measured under hydrogen production conditions. The capability for hydrogen photoproduction in cells was correlated with that of cellular carbohydrate content. Cells with a high carbohydrate content exhibited a high capacity for hydrogen production and those with low carbohydrate content exhibited low capacity for hydrogen production. Nitrogenase activity at the onset of incubation did not coincide with a capability for the cells to produce hydrogen during the subsequent incubation period. Interestingly, when cells with a high capacity for hydrogen photoaccumulation were incubated, alternate periods of hydrogen and oxygen accumulation were observed at 12 hour intervals. About 0.5 ml of hydrogen per ml of cell suspension was accumulated in flasks during the initial 12-h incubation period. These observations indicate that the use of synchronous culture can be one of the ways of provide materials suitable not only for basic studies but also for applied aspects of hydrogen photoproduction.     

Large-amplitude internal waves benefit corals during thermal stress

Tropical scleractinian corals are particularly vulnerable to global warming as elevated sea surface temperatures (SSTs) disrupt the delicate balance between the coral host and their algal endosymbionts, leading to symbiont expulsion, mass bleaching and mortality. While satellite sensing of SST has proved a reliable predictor of coral bleaching at the regional scale, there are large deviations in bleaching severity and mortality on the local scale that are poorly understood. Here, we show that internal waves play a major role in explaining local coral bleaching and mortality patterns in the Andaman Sea. Despite a severe region-wide SST anomaly in May 2010, frequent upslope intrusions of cold sub-pycnocline waters due to breaking large-amplitude internal waves (LAIW) mitigated coral bleaching and mortality in shallow waters. In LAIW-sheltered waters, by contrast, bleaching-susceptible species suffered severe bleaching and total mortality. These findings suggest that LAIW benefit coral reefs during thermal stress and provide local refugia for bleaching-susceptible corals. LAIW are ubiquitous in tropical stratified waters and their swash zones may thus be important conservation areas for the maintenance of coral diversity in a warming climate. Taking LAIW into account can significantly improve coral bleaching predictions and provide a valuable tool for coral reef conservation and management.     

The intersectional hybrid between Weigela hortensis and W. maximowiczii (Caprifoliaceae)

Morphologically intermediate plants between Weigela hortensis (Siebold & Zucc.) K.Koch and W. maximowiczii (S.Moore) Rehder have been found in Miyagi and Yamagata Pref., northern Japan. Quantitative character analyses of flowers, pollen stainability and molecular analyses indicated that the intermediate plants were hybrids of those two species. This is the first record of an intersectional hybrid with W. maximowiczii (sect. Weigelastrum ) as one of the parent species. The morphological differences among hybrid individuals imply the possibility of backcrosses or formation of second or later generations of hybrids, although those may be quite rare because of a low frequency of viable pollen grains. Causes of hybridization between two distantly-related species in Weigela are discussed. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 369–380.     

Molecular data reveal convergence in fruit characters used in the classification of Thlaspi s. I. (Brassicaceae)

Phylogenetic relationships of 18 Thlaspi s.l. species were inferred from nuclear ribosomal internal transcribed spacer (ITS) sequence data. These species represent all sections of the basic classification system of Schulz primarily based on fruit characters. The molecular phylogeny supported six clades that are largely congruent with species groups recognized by Meyer on the basis of differences in seed coat anatomy, i.e. Thlaspi s. s., Thlaspkeras, Moccaea {Raparia included), Microthhspi, Vania and Neurotropy. Some of these lineages include species which are morphologically diverse in fruit shape (e.g. Thlaspi s. s.: T. arvense - fruits broadly winged, T. ceratocarpum - fruits with prominent horns at apex, T. alliaceum - fruits very narrowly winged). Furthermore, the same fruit shape type is distributed among different clades. For instance, fruits with prominent horns at apex are found in Thlaspi s. s. ( T. ceratocarpum) and Thlaspiceras (T oxyceras). These results clearly indicate convergence in fruit characters previously used for sectional classification in Thlaspi s. l.     

Prehistoric mongoloid dispersals. Edited by Takeru Akazawa and Emöke J. E. Szathmáry. New York: Oxford University Press. 1996. 387 pp. ISBN 0-19-852318-1 $150.00 (cloth)

Studies of the dynamics of locomotor performances depend on knowledge of the distribution of body mass within and between limb segments. However, these data are difficult to derive. Segment mass properties have generally been estimated by modelling limbs as truncated cones, but this approach fails to take into account that some segments are of elliptical, not circular, cross section; and further, the profiles of real segments are generally curved. Thus, they are more appropriately modelled as solids of revolution, described by the rotation in space of convex or concave curves, and the possibility of an elliptical cross section needs to be taken into account. In this project we have set out to develop a general geometric model which can take these factors into account, and permit segment inertial properties to be derived from cadavers by segmentation, and from living individuals using linear external measurements. We present a model which may be described by up to four parameters, depending o the profile and serial cross section (circular or ellipsoidal) of the individual segments. The parameters are obtained from cadavers using a simplified complex-pendulum technique, and from intact specimens by calculation from measurements of segment diameters and lengths. From the parameters, the center of mass, moments of inertia, and radii of gyration may be derived, using simultaneous equations. Inertial properties of the body segments of four Pan troglodytes and a single Pongo were determined, and contrasted to comparable findings for humans. Using our approach, the mass distribution characteristics of any individual or species may be represented by a rigid-link segment model or “android.” If this is made to move according to motion functions derived from a real performance of the individual represented, we show that recordings of resulting ground reaction forces may be quite closely simulated by predictive dynamic modelling. © 1996 Wiley-Liss, Inc.