Question: How resilient is the seed bank of an invaded dune system? Is that resilience dependent on duration of invasion? How does the accumulated litter layer contribute to the soil seed bank?



Location: Coastal sand dunes invaded by Acacia longifolia, Portugal.



Methods: Seedling emergence was used to quantify and compare soil seed banks in long-invaded, recently invaded and non-invaded areas. Changes in seed banks were also compared with areas where A. longifolia and the litter layer were removed.



Results: Species richness, seedling density and diversity were higher in non-invaded and recently-invaded areas than in long-invaded areas. Although there was an apparent similarity between non-invaded and recently-invaded areas, analyses of species traits revealed differences. Non-invaded areas had a wider array of traits. Exotic/invasive species dominated invaded seed banks while native species dominated non-invaded seed banks. Life forms, growth forms, longevity and dispersal mode showed differences between areas, with cleared plots of long-invaded areas being apparently the most similar to non-invaded plots. Acacia longifolia seeds were most abundant in long-invaded areas, particularly where the litter layer remained. Removal of A. longifolia plus the litter had little effect on the seed bank composition of recently-invaded areas but resulted in noticeable changes in seed banks of long-invaded areas.



Conclusions: Long-invaded areas are less resilient and show a higher reinvasion potential, despite severe alteration of the seed banks of both areas. Seed bank studies can be a useful tool to guide management, but can give misleading results when invasion periods are protracted.

The potential role of seed banks in the recovery of dune ecosystems after removal of invasive plant species.

Taro [Colocasia esculenta (L.) Schott] is an ancient, tropical root crop that is morphologically diverse with over 10,000 landraces. It is the fifth most produced root crop in the world and is mainly grown in tropical Africa, China, New Guinea, and many Pacific islands. Taro typically is grown for its starchy corm (i.e., underground stem), although leaves and flowers also are eaten as vegetables. There is controversy over its geographic center of origin, but this is likely to be in the Indo-Malayan area. Evidence indicates that it was domesticated, possibly independently, across an area that ranges from northeast India to Yunnan province in China to New Guinea. Within Micronesia and Polynesia, where taro is a staple crop, the genetic base is very narrow. Genetic diversity within the taro germplasm is significantly greater in Asia and New Guinea. The exploitation of this diversity could lead to the development of cultivars with greater disease resistance, and improved yields and corm quality. Taro is a neglected crop in terms of recent advances in molecular biology, with only a limited number of studies utilizing next-generation transcriptome and genome sequencing. At present, a high-quality reference genome is lacking; however, recent genotyping-by-sequencing (GBS) approaches promise to improve our understanding of taro genetics.

Genetic Diversity in Taro ( Colocasia esculenta )

Cytogenetical studies were carried out on Colocasia esculenta (L.) Schott and five different karyotypes were observed, karyotype formula of each karyotype were 2n=28=L24 m +M4, 2n=28=L14 +L2+M6+M6, 2n=28=L22 m +L6, 2n=28=L18 m +M4+M2+S2+S2 and 2n=28=L8+L4+M4+M10 +S2. The karyotype of five strains had same chromosome number of 2n=28 and fundamental number (NF)=56. Therefore, all of the five strains had a symmetrical karyotype that consisted of metacentric and submetacentric chromosomes. The differences among karyotypes were caused by number of metacentric and submetacentric chromosomes. The chromosome number of C. esculenta had been reported, but this is the first report of karyotype variation among strains.

Comparative Karyotype Analysis in Five Strains of Colocasia esculenta (L.) Schott (Araceae) in Thailand

For six years Dr Strehler was an important contributor to progress in the study of bioluminescence and of adenosine triphosphate synthesis during photosynthesis For the last six years he has been chief of the Cell and Comparative Physiology Section of the Gerontology Branch, National Institutes of Health This book represents his study and formulation of the problems of aging Ten pages are devoted to the definition, measurement, and determination of direction of flow of time and show rigorous study of a basic factor in aging Many medical readers, like the reviewer, may skip rather quickly over the next hundred pages containing a review of theoretical approaches, and concentrate on chapters V, VI, and VII, which describe the effects of tissue, cellular, and subcellular aging They may also hurry through the last 40 pages, again on the theories and on problems for the investigator But they will find everywhere concise writing

Time, Cells, and Aging.

Chromosome number and genome size are important cytological characters that significantly influence various organismal traits. We investigated chromosome number and genome size variation in 73 accessions belonging to four Colocasia species from China. Five different chromosome counts (2n = 26, 28, 38, 42, and 56) were found, the largest one representing a new record in Colocasia. The basic chromosome numbers are x = 13, 14, and 19, corresponding to 2x, 3x, and 4x cytotypes. Yunnan Province, China is considered the center of Colocasia polyploid origin. The 2C values in our accessions ranged from 3.29 pg in C. gigantea to 12.51 pg in C. esculenta. All species exhibit inter- and intraspecific chromosomal variation. Differences in DNA content among the Colocasia species seem to have occurred by chromosomal gain under similar habitats. Polyploidization also obviously contributes to 2C value variation.

Chromosome number and genome size variation in Colocasia (Araceae) from China.

Nuclear and chromosome characteristics of seven varieties of Colocasia esculenta were studied. Interphase chromosome value was found to range from 2119.85 (cytotype-3) to 5346.12 (cytotype-7). Heterochromatin values varied from 23.17 (cytotype-2) to 44.52% (cytotypt-6) in meristematic cells. Karyotype studies revealed that somatic chromosome number was 28 in cytotype-1, 2, 5, 6 and 7; 42 in cytotype-3 and 21 in cytotype-4. The longest chromosome (5.54 μm) was observed in cytotyopt-2 and shortest (1.3 μm) in cytotype-3 and 6. Key words: Karyotype, Nuclear phenotype, Colocasia esculenta. DOI:10.3329/jbs.v16i0.3735  J. bio-sci. 16: 15-18, 2008

/pdf/karyotype-analysis-of-seven-varieties-of-taro-colocasia-3gtmrehcww.pdf

Karyotype Analysis of Seven Varieties of Taro Colocasia esculenta (L.) Schott. from Bangladesh

Post-irradiation ageing effect on seed germinability and different morphological characters of Crotalaria saltiana were studied in the year of 2006. Germination percentage of Crotalaria saltiana seeds treated with different doses of gamma rays, aged for 32 years in moisture free condition showed remarkable variation. Plants grown from the treated seeds of all the doses showed diversity among themselves regarding their morphological characters. Such as plant height was found to reduce in lower doses and this character showed no such consistent result. Leaf irregularities such as, invaginated margin, inverted margin with blunt apex, leaf with bifurcated apex, small size and dented margin, etc. were recorded. Key words: Post-irradiation ageing effect, Morphological characters, Crotalaria saltiana . DOI:10.3329/jbs.v16i0.3747 J. bio-sci. 16: 89-93, 2008

/pdf/post-irradiation-ageing-effect-on-morphological-characters-1e3wtzflo3.pdf

JK Sarker

Papers

Karyotype Analysis of Seven Varieties of Taro Colocasia esculenta (L.) Schott. from Bangladesh

Post-Irradiation Ageing Effect on Morphological Characters of Crotalaria saltiana