José Marcelo Domingues Torezan

Karyotype differentiation of four Cestrum species (Solanaceae) based on the physical mapping of repetitive DNA

We studied the karyotypes of four Brazilian Cestrum species (C. amictum, C. intermedium, C. sendtnerianum and C. strigilatum) using conventional Feulgen staining, C-Giemsa and C-CMA3/DAPI banding, induction of cold-sensitive regions (CSRs) and fluorescent in situ hybridization (FISH) with rDNA probes. We found that the karyotypes of all four species was 2n = 2x = 16, with, except for the eighth acrocentric pair, a predominance of meta- and submetacentric chromosomes and various heterochromatin classes. Heterochromatic types previously unreported in Cestrum as neutral C-CMA30/DAPI0 bands, CMA3+ bands not associated with NORs, and C-Giemsa/CSR/DAPI- bands were found. The heterochromatic blocks varied in size, number, position and composition. The 45S rDNA probe preferentially located in the terminal and subterminal regions of some chromosomes, while 5S rDNA appeared close to the centromere of the long arm of pair 8. These results suggest that karyotype differentiation can occur mainly due to changes in repetitive DNA, with little modification in the general composition of the conventionally stained karyotype.

Genetic variability of pre and post-fragmentation cohorts of Aspidosperma polyneuron Muell. Arg. (Apocynaceae)

RAPD was used to access the genetic variability in Aspisdosperma polyneuron, a long-lived, late-reproducing tropical tree, and highly important for the Atlantic Forest. RAPD profiles from adults (pre-fragmentation, >300 years old) and seedlings (post-fragmentation, <<50 years old) were analyzed. Results showed a decrease of genetic polymorphism of post-fragmentation cohorts in small fragments and higher genetic diversity within population. The genetic diversity distribution suggested the establishment of fragments as protected reserves, and the transference of seedlings among fragments for conservation of A. polyneuron.

Cytogenetical and cytotaxonomical analysis of some Brazilian species of Eleocharis (Cyperaceae)

Karyotype analysis of 21 samples of 11 species of Eleocharis (Cyperaceae) from 10 localities in Brazil, showed the presence of chromosomes without primary constrictions and parallel movement of chromatids at metaphase–anaphase transition. Only the terminal nucleolar constrictions (satellites) were visualised. The chromosome numbers varied from 2n = 6 in E. subarticulata to 2n = 54 in E. acutangula, but the chromosome basic number x = 5 was confirmed. Generally, C-CMA3+ bands appear mostly in the extremities of the chromosomes, associated to NOR, and interstitial C-CMA3 bands were found only in E. geniculata and E. acutangula. C-DAPI+ bands were not found. Fluorescence in situ hybridisation (FISH) with the 45S rDNA probe was performed in five species. The results showed from four to eight hybridisation signals, always terminal. The analysed species include representatives of the following three subgenera of Eleocharis that occur in Brazil: Limnochloa, Scirpidium and Eleocharis. Species from the subgenus Limnochloa have small and numerous chromosomes. The remaining species, belonging to subgenera Eleocharis and Scirpidium, possess fewer and larger chromosomes. In subgenus Eleocharis, karyotypes of the section Eleocharis were differentiated by symploidy, agmatoploidy and polyploidy, whereas species of the section Eleogenus were all polyploids. Polyploidy seems to be the most frequent event in the karyotype differentiation in Eleocharis, but changes in the chromosome size and repetitive DNA sites were also observed.

Inoculação de fungos micorrízicos arbusculares e adubação na formação e pós-transplante de mudas de cinco espécies arbóreas nativas do sul do Brasil

(The effects of arbuscular mycorrhizal fungi inoculation and fertilization on initial growth and post-transplant of seedlings of five native woody species from southern Brazil). This study assessed the effects of arbuscular mycorrhizal fungi (AMF) inoculation and application of different doses of fertilizer on initial growth and post-transplant seedlings of five native woody species from south Brazil: Croton urucurana Baill. (Euphorbiaceae), Senna macranthera (Collad.) H.S. Irwin & Barneby (Caesalpiniaceae), Anadenanthera colubrina (Veil.) Brenan (Mimosaceae), Bastardiopsis densiflora (Hook. & Arn.) Hassl. (Malvaceae) and Bauhinia forficata Link (Caesalpiniaceae). The experiment was set up as a 3x2 factorial, with three fertilization levels, with or without AMF inoculation. For six months in the nursery, data were collected on vegetative growth, inoculation response and colonization by AMF. The roots showed medium to high mycorrhizal colonization (54-77%), but low arbuscular formation (3-9%). The low response to inoculation among plant species was related to substrate characteristics, which were considered inadequate for ideal development of the mycorrhizal association. Plants growing in substrate with greater mineral addition gave the bestresults in the nursery, regardless of AMF inoculation. After six months growing in the field, plants of the basic substrate treatment showed a relative growth rate significantly higher than the fertilized ones. After six months in the field, survival rate was 3 to 30% higher for seedlings that grew without fertilization and were inoculated with AMF when compared to those without inoculation. For most of the species, the combination of inoculation and fertilization did not afford positive results in seedling field survival.

Comparando metodologias para avaliar a cobertura do dossel e a luminosidade no sub-bosque de um reflorestamento e uma floresta madura

The objectives of this work were: (1) to investigate the efficiency, advantages and disadvantages of five methodologies to evaluate canopy structure (eco-unit interpretation, spherical densiometer, hemispheric photography with 8 mm lens and digital photography with 32 mm lens) and the amount of light crossing it (using light meter and hemispheric photography with 8 mm lens) and (2) to compare the canopy structure of a reforestation area and a semideciduous forest fragment in northern Parana. The classification of forest mosaic in eco-units is a fast and cheap methodology, but it lacks repeatability. Densiometer provides fast and reliable measurements, while light meter and 32 mm lens present data with little precision, being thus sensitive to small variations in the canopy; 8 mm lens is a fast and high precision methodology but expensive. No significant difference was found in the canopy cover estimates between densiometer and the 8 mm lens photography in either of the two sites, while 32 mm lens photography showed significantly different results and great mena variation, due to high sensitivity to the small alterations in the canopy. The luminosity evaluation showed significantly different light meter and 8 mm lens photography. All the methodologies showed significant differences between the mature forest and the reforestation area.

A karyotypic study of three southern Brazilian Asteraceae species using fluorescence in situ hybridization with a 45S rDNA probe and C-CMA3 banding

The Asteraceae, one of the largest families of flowering plants, contains about 1,100 genera and 20,000 species, and is well known for its extensive karyotypic variation. In this study, conventional Feulgen staining, C-CMA3 banding, and fluorescence in situ hybridization with a 45S rDNA probe were used to determine the chromosome number and the number and physical position of GC-rich heterochromatin and 45S rDNA sites in three Asteraceae weed species (Crepis japonica, Galinsoga parviflora and Chaptalia nutans). The three species exhibited karyotype differences in the chromosome number and shape, as a commom feature of Asteraceae. However, the 45S rDNA sites always occurred on the short chromosomal arms, associated with GC-heterochromatin. Althought of these differences, it suggests that commom features of plant karyotype are maintained.

Produção de serapilheira e ciclagem de nutrientes de um reflorestamento e de uma floresta estacional semidecidual no sul do Brasil

A producao, o conteudo de N, P, K, Ca e Mg, a transferencia de nutrientes e a taxa de decomposicao da serapilheira foram estudados em uma Floresta Estacional Semidecidual e em um reflorestamento situado adjacente a esta no Parque Estadual Mata dos Godoy, Estado do Parana, Brasil. A deposicao anual de serapilheira foi estimada em 8.212 kg.ha-1.ano-1 na floresta e 5.341 kg.ha-1.ano-1 no reflorestamento. A floresta apresentou nos dois meses apos a seca (setembro e outubro) maior deposicao. Nas duas areas a media anual da concentracao de macronutrientes em g.kg-1, obedeceu a mesma ordem na floresta Ca(31,85) > N(19,94) > K(7,14) > Mg(2,28) > P(0,217) e no reflorestamento Ca(23,02) > N(19,62) > K(7,67) > Mg(1,74) > P(0,302). No reflorestamento a transferencia de nutrientes variou mais durante o ano e a taxa de decomposicao foi menor.

Microhabitat preferences of six Drosera (Droseraceae) from Tibagi river basin, Paraná state, Brazil

We studied the microhabitats and the climatic requirements of six Drosera taxa, which occur in the subtropical grasslands of the Tibagi river basin. They are annual,or most communly, perennial herbs known as carnivorous plants, whose leaves are transformed into traps for the capture and digestion of small insects as an adaptation for supplying nutricional deficiencies. They usually occur in distrophic substrata. In order to contribute to conservation plans for the species of the genus, threatened by the conversion of the natural grasslands into pastures, we tried to define their preferential habitats and climatic requirements. We verified that the variables of microhabitat and altitude presented significant correlation at 5% probability level, while the variables in annual average relative humidity, annual average temperature and type of substratum types did not show significant correlation.

Functionality of major and minor 45S rDNA sites in different diploid wild species and varieties of sunflowers

Abstract The genus Helianthus includes diploid (2n = 2x = 34), tetraploid (2n = 4x = 68) and hexaploid (2n = 6x = 102) species, and genome evolution based on extensive diversity due to free hybridization, introgression and polyploidy. The wild diploid species H. debilis, H. praecox and H. nuttallii showed 2n=34 with four 45S rDNA sites. The cultivated sunflower (H. annuus), also diploid, showed six and eight 45S rDNA sites, being six major and two minor terminal rDNA sites. Samples were studied using C-CMA3 and NOR banding to determinate the functionality of minor 45S rDNA sites. Additionally, FISH with 45S and 5S rDNA probes were performed. Results showed that the number and the position of 45S and 5S rDNA sites maintenance in cultivated karyotypes, but provide evidence of a possible increasing in number of rDNA 45S sites when compared with the wild diploid species. Besides, results of C-CMA3 and NOR banding showed that the minor sites are not associated with GC-rich heterochromatin but, even thus, are functional.

Factors affecting the genesis of vegetation patches in anthropogenic pastures in the Atlantic forest domain in Brazil

Background: Forest succession in tropical pastures usually starts from woody vegetation patches. Patches may arise within the grass matrix at microsites with favourable soil conditions or through facilitation by established nurse plants. Aims: We report the formation of woody vegetation patches in tropical pastures after investigating whether patch formation was associated with micro-scale terrain features and whether facilitation was important for patch initiation. Methods: The study was conducted in three pasture sites in the Atlantic forest domain of Brazil. We compared soil, terrain and species abundance patterns among pairs of woody patch and open pasture plots. Results: The effect of variation in soil physical and chemical attributes was limited. Some species were able to establish in the grass matrix and survive disturbance from grazing and fire, while other species only established in patches, under other already established trees or shrubs. Some of these species were exotics, which are commonly eliminated in restoration efforts. Conclusions: Allowing the establishment of species capable of withstanding pasture environments, including exotics, can accelerate succession. Furthermore, the abilities to endure competition from grasses and survive fire are key features of species suitable for the initial stages of forest restoration in tropical pastures.