Effect of the seed coat on water uptake and electrolyt leakage of sorghum (Sorghum bicolor (L.) Moench) seeds

Four seed lots of sorghum cultivar IS 34213 were obtained which had been harvested early or at full maturity and then dried either swiftly in the sun or slowly in the shade. The earlier harvested seeds were lighter, smaller and of lower density. Earlier harvested seeds had pericarps which permitted faster water uptake and greater leakage of electrolytes. Water uptake and electrolyte leakage were positively correlated. The method of seed drying had no effect on water uptake or leakage. Greater leakage was associated with lower final germination. The results are interpreted in relation to germination testing.     

Availability of mineralized N from microbial biomass and organic matter after drying and heating of grassland soils

A dwarf bamboo-type grassland soil (Thick High-humic Andosol) was nitrogen-limited for grass despite the presence of a considerable amount of microbial biomass N. By either treatments of air-drying and subsequent heating, the content of mineral N in the soil was increased by 3.7 g N and 11.7 g N m^-2, respectively, after a 55-day incubation period. The efficiency of mineralized N for growth of orchardgrass was compared with nitrate-N added just before cultivation. The dry matter content of the grass increased from 81.7 g (control) to 169 g and to 337 g m^-2 in the dried and in the heated soils, respectively, when N application was omitted. Of the mineral N released by air-drying and heating of the soil, 84% and 77% were absorbed by the grass, and 30% and 20% was assumed to be derived from microbial biomass, respectively. In contrast the grass apparently absorbed 54–56% of the 5 g nitrate-N m^-2 added to the control and the air-dried soils. It was also noted that fungal biomass N had decreased by 1.5–1.9 g m^-2 in the control soil after addition of 10 g nitrate-N m^-2.     

Differentiation Between Acetylated and Nonacetylated PAS-Reactive Mucosubstances

The air drying technique, widely used in animal cytogenetics, was adapted for use with Zea mays L. chromosomes. Using a simple protocol without enzymatic maceration and avoiding the inconvenience of the squashing technique, good staining and C-banding were obtained from maize chromosome preparations.     

Xeroprotectants for the stabilization of biomaterials

With the advancement of science and technology, it is crucial to have effective preservation methods for the stable long-term storage of biological material (biomaterials). As an alternative to cryopreservation, various techniques have been developed, which are based on the survival mechanism of anhydrobiotic organisms. In this sense, it has been found that the synthesis of xeroprotectants can effectively stabilize biomaterials in a dry state. The most widely studied xeroprotectant is trehalose, which has excellent properties for the stabilization of certain proteins, bacteria, and biological membranes. There have also been attempts to apply trehalose to the stabilization of eukaryotic cells but without conclusive results. Consequently, a xeroprotectant or method that is useful for the stable drying of a particular biomaterial might not necessarily be suitable for another one. This article provides an overview of recent advances in the use of new techniques to stabilize biomaterials and compare xeroprotectants with other more standard methods.     

High-voltage electron microscopy of whole,critical-point dried plant cells—fine cytoskeletal elements in the mossBryum tenuisetum

Summary Whole, critical-point dried cells of protonemata of the mossBryum tenuisetum have been examined in the high-voltage electron microscope at 1 MV. Fine cytoskeletal elements form a three-dimensional meshwork in the cytoplasm. This resembles, but has some differences from, the microtrabecular lattice seen in spread animal cells examined by the same technique.     

The fruit of their labour: plants and plant processing at EeRb 140 (860±60 uncal B.P. to 160±50 uncal B.P.), a late prehistoric hunter-gatherer-fisher site on the southern Interior Plateau, British Columbia, Canada

Palaeoethnobotanical analysis of Late Period contexts (860±60 uncal B.P. to 160±50 uncal B.P.) at the site of EeRb 140, indicates that it probably served as a seasonal work area, utilised during the mid to late summer by the residents of an adjacent pit-house winter village. Food processing was evidently the primary plant-related activity at this open-air hunter-gatherer-fisher site on the British Columbia Plateau in Canada. One feature appears to have functioned as both an open hearth for the drying and preservation of berries and as a pit-oven, possibly for preparing foods for immediate consumption. Comparisons of the archaeobotany of EeRb 140 with Plateau ethnographies suggest that women's task group activities are represented here. Most significantly, the identification of a specialised plant-processing site in such close proximity to a winter village contrasts strongly with existing ethnoarchaeological models for the British Columbia Plateau and introduces a type of site not previously identified archaeologically in this region. Received August 14, 2001 / Accepted March 13, 2002     

Fragmentation promotes the role of dispersal in determining 10 intermittent headwater stream metacommunities

1. Dispersal, defined as the movement of individuals among local communities in a landscape, is a central regional determinant of metacommunity dynamics in ecosystems. Whereas both natural and anthropogenic ecosystem fragmentations can limit dispersal, previous attempts to measure such limitations have faced considerable context dependency, due to a combination of spatial extent and associated environmental variability, the wide range of dispersal modes, and abilities of organisms or variation in network topologies. Therefore, the role dispersal plays compared to local environmental filtering in explaining metacommunity dynamics remains unclear in fragmented dendritic ecosystems.
2. We quantified α- and β-diversity components of invertebrate metacommunities across 10 fragmented headwater stream networks and tested the hypothesis that dispersal is the primary determinant of biodiversity organisation in these dynamic and spatially constrained ecosystems.
3. Alpha-diversity was much lower in intermittent than perennial reaches, even long after rewetting, indicating an overwhelming effect of drying including a legacy effect on local communities.
4. Beta-diversity was never correlated with environmental distances but predominantly explained by spatial distances accounting for river network fragmentation. The nestedness proportion of β-diversity was considerable and reflected compositional differences where communities from intermittent reaches were subsets of perennial reaches.
5. Altogether, these results indicate dispersal as the primary process shaping metacommunity dynamics in these 10 headwater stream networks, where local communities recurrently undergo extinction and recolonisation events. This challenges previous conceptual views that local environment filtering is the main driver of headwater stream metacommunities.
6. As river networks become increasingly fragmented due to global change, our results suggest that some freshwater ecosystems currently driven by local environment filtering could gradually become dispersal-limited. In this perspective, shifts from perennial to intermittent flow regimes represent ecological thresholds that should not be crossed to avoid jeopardising river biodiversity, functional integrity, and the ecosystem services they provide to society.