Morphological changes during akinete germination in Cylindrospermopsis raciborskii (Nostocales, Cyanobacteria)

The occurrence of the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) Seenayya and Subba Raju is a global water quality issue. The misidentification of C. raciborskii in the past is a major concern for water quality users, considering the reported cases of human and livestock poisonings associated with the cyanobacterium. Many of the available taxonomic descriptions for this species provide little or no detail of the morphology of early developmental phases that may assist with identification. Therefore, typifying the morphological changes throughout the entire life cycle for such a species requires urgent attention. In this study, five distinct morphological phases identified using a new culturing technique are reported for the process of akinete germination in C. raciborskii. Before the terminal emergence of three to four cell germlings through a ruptured akinete envelope (phase 3), mature akinetes (phase 1) elongated and the endospore separated from the akinete envelope (phase 2). After the association with the envelope was lost, four-cell germlings (phase 4a) matured into young trichomes of more than four cells (phase 4b). Throughout the process of germination, internal granular structures decreased in size and were irregular in shape in germlings and young trichomes. The culturing technique, which used a Sedgwick-Rafter cell, was successful in its application but was limiting in that the development of young trichomes after phase 4b could not be monitored.

Marine isocyanides and related natural products structure, biosynthesis and ecology

This review highlights structural and biosynthetic work on a group of nitrogen-functionalised terpenes that are almost exclusively found in marine invertebrates and the animals that feed on them. The chemical functionality reviewed includes isocyanides, isothiocyanates, formamides, thiocyanates, isocyanates, and dichloroimines. The literature through mid 2003 is reviewed and there are 143 citations.

Phosphorus uptake from green manures and phosphate fertilizers applied in an acid tropical soil

Quantifying the relative contribution of different phosphorus (P) sources to P uptake can lead to greater understanding of the mechanisms that increase available P in integrated P management systems. The P-32-P-33 double isotope labeling technique was used to determine the relative contribution of green manures (GMs) and P fertilizers to P uptake by Setaria grass (Setaria sphacelata) grown in an amended tropical acid soil (Bungor series) in a glasshouse study. The amendments were factorial combinations of GMs (Calopogonium caeruleum , Gliricidia sepium and Imperata cylindrica) and P fertilizers [phosphate rocks (PRs) from North Carolina (NCPR), China (CPR) and Algeria (APR), and triple superphosphate (TSP)]. Dry matter yield, P uptake, and P utilization from the amendments were monitored at 4, 8, and 15 weeks after establishment (WAE). The GMs alone or in combination with P fertilizers contributed less than 5% to total P uptake in this soil, but total P uptake into Setaria plants in the GM treatments was three to four times that of the P fertilizers because the GMs mobilized more soil P. Also, the GMs markedly increased fertilizer P utilization in the combined treatments, from 3% to 39% with CPR, from 6-9% to 19-48% with reactive PRs, and from 6% to 37% with TSP in this soil. Both P GM and the other decomposition products were probably involved in reducing soil P-retention capacity. Mobilization of soil P was most likely the result of the action of the other decomposition products. These results demonstrate the high potential of integrating GMs and PRs for managing P in tropical soils and the importance of the soil P mobilization capacity of the organic components. Even the low-quality Imperata GM enhanced the effectiveness of the reactive APR more than fourfold.

Rehabilitating degraded forest land in central Vietnam with mixed native species plantings

This paper examines the use of Acacia as a nurse crop to overcome some of the ecological and economic impediments to reforestation of degraded areas dominated by grasses including Imperata cylindrica. The study site at Hai Van Pass in central Vietnam was initially reforested using Acacia auriculiformis. After 8 years these stands were thinned and under-planted with Hopea odorata, Dipterocarpus alatus, Parashorea chinensis, Tarrietia javanica, Parashorea stellata, Scaphium lychnophorum, Peltophorum dasyrhachis var. tonkinensis and other high-value native species. At the time of field assessment (early 2004), the Acacia trees were aged between 16 and 18 years and basal area ranged from 9 to 13 m(2) ha(-1) after several thinnings. Acacias facilitated the establishment of native species, but after 6-7 years of growth, further thinning is needed to maintain growth rates. In addition to assisting the establishment of native species, the Acacia nurse crop should provide a revenue stream (NPV about US$ 180, or IRR 19%) sufficient to cover the establishment costs of the underplanted native species (about US$ 100). (c) 2006 Published by Elsevier B.V.