Distribution of aluminium in accumulator plants by X-ray microanalysis in Richeria grandis Vahl leaves from a cloud forest in Venezuela

Abstract. The leaf cells of a tropical tree which accumulates more than 1mg per gram dry weight of Al in its leaves were studied by X-ray microanalysis. The analyses made in cell walls, vacuoles and chloroplasts of a mature leaf showed that A1 is accumulated preferentially in the cell wall. In the pre-senescent leaf, A1 also invades the interior of cells and is deposited in chloroplasts and vacuole. Aluminium was found also in xylem vessels but only in traces in phloem tissue. It was not found in spongy parenchyma cells. The observed A1 distribution, i.e. at the adaxial leaf face, coincides with observed damage in tissues of pre-senescent leaves. The means by which this plant copes with Al under natural conditions seems to be partially preventing it from entering the cell by deposition in cell walls. A hypothesis about the pathways of Al in accumulator plants is proposed.     

Breeding Systems of Three Tree Ferns: Alsophila firma (Cyatheaceae), Cyathea stipularis (Cyatheaceae), and Lophosoria quadripinnata (Lophosoriaceae)

Abstract Breeding-system data have been available for a large number and diverse array of angio-sperms for a relatively long time. In contrast, breeding systems of ferns and their allies (pteridophytes) have only recently been examined, and breeding-system data from natural populations of sporophytes are still lacking for pteridophytes representing many life-history strategies. Few studies, for example, have examined breeding systems of tropical pteridophytes, and no breeding-system data are available for tree ferns. We therefore examined the breeding systems of three species of tree ferns from Costa Rica, Alsophila firma (Cyatheaceae), Cyathea stipularis (Cyatheaceae), and Lophosoria quadripinnata (Lophosoriaceae) using enzyme electro-phoresis. Genetic data were used to estimate intragametophytic self-fertilization and F , the fixation index. Analysis of genetic data indicates that the gametophytes of these three species predominantly cross-fertilize; all three species would be characterized as outcrossers. However, some population-to-population variation in breeding system was detected in all three species. Outcrossing also typifies a diverse array of temperate ferns. Thus, despite the potential for self-fertilization, outcrossing appears to characterize the majority of pteridophytes representing a variety of evolutionary lineages, life-history strategies, and environments.     

An alternative approach for gene transfer in trees using wild-typeAgrobacterium strains

Micropropagated shoots of three forest tree species, poplar (Populus tremula × P.alba), wild cherry (Prunus avium L.) and walnut (Juglans nigra × J. regia), were inoculated each with six different wild-typeAgrobacterium strains. Poplar and wild cherry developed tumors that grew hormone-independently, whereas on walnut, gall formation was weak. On poplar and wild cherry, tumors induced by nopaline strains developed spontaneously shoots that had a normal phenotype and did not carry oncogenic T-DNA. From these observations, we have established a co-inoculation method to transform plants, using poplar as an experimental model. The method is based on inoculation of stem internodes with anAgrobacterium suspension containing both an oncogenic strain that induces shoot differentiation and a disarmed strain that provides the suitable genes in a binary vector. We used the vector pBI121 carryingneo (kanamycin resistance) anduidA (-glucuronidase) genes to facilitate early selection and screening. Poplar plants derived from kanamycin-resistant shoots that did not carry oncogenic T-DNA, were shown to contain and to expressneo anduidA genes. These results suggest that wild-typeAgrobacterium strains that induce shoot formation directly from tumors can be used as a general tool for gene transfer, avoiding difficult regeneration procedures.This work is dedicated to the late Marie-France Michel who initiated the poplar biotechnology project at INRA.     

Effects of defoliation on the saplings of a gap-colonizing neotropical tree

This paper describes a defoliation experiment on saplings of the gap-colonizing pioneer tree Heliocarpus appendiculatus in the tropical rain forest of Los Tuxtlas (Southeast Mexico). Four levels of defoliation (0, 25, 50, and 75% of the leaf area removed) were applied to naturally established plants in a medium-sized forest gap. Records were made of growth (height, diameter, and leaf production) and of whole-plant and leaf survival. Statistical comparisons for all variables showed that plants that had not been defoliated grew better than defoliated ones, but there were no statistically significant differences between the defoliation levels. The risk of death was significantly lower for control plants than for defoliated plants at any level of damage. Leaf survivorship was highly irregular. The most consistent pattern was that the leaves of intact plants always showed higher survivorship, while the most heavily defoliated ones always had the poorest survival. The survivorship pattern of leaves at intermediate defoliation levels was irregular. The results illustrate the lack of a monotonic response to a wide range of defoliation levels, and suggest the potential effect of herbivores as reducers of vegetative growth and survival in pioneer tropical species, and as limiting agents of plant establishment in regenerating forest gaps.     

Distribution of seedlings and saplings of Quercus robur in a grazed deciduous forest

Seedling and sapling distribution of the deciduous tree Quercus robur was, studied in a grazed, partly open forest, ca. 20 km S of Linkoping, Sweden. Numbers of seedlings and saplings were compared between open and shaded parts of the forest. Cover values for the shrub and tree layers, proportion of bare ground and of stones and soil water content were determined. Q. robur was shown to germinate equally well in open and shaded parts of the forest; however, most saplings were found in the shade. No correlation was found between seedlings or saplings and cover of shrub layer or proportion of stones in the soil surface or with soil water content.     

Evolving sea urchin histone genes-nucleotide polymorphisms in the H4 gene and spacers ofStrongylocentrotus purpuratus

Summary We present a comparison of spacer and coding sequences of histone gene repeats from fourStronglycocentrotus purpuratus individuals. Sequences of two previously cloned units (pCO2 and pSp2) were compared with three new histone gene clones, two of them from a single individual. Within a 1.7-kb region, 59 polymorphic sites were found in spacers, in mRNA nontranslated stretches, and at silent sites in codons of the H4 gene. The permitted silent-site changes were as frequent as in any other region studied. The most abundant polymorphisms were single-base substitutions. The ratio of transitions: tranversions: single-base-pair insertions/deletions was 322. A number of larger insertions/deletions were found, as well as differences in the length of (CTA)_n and (CT)_n runs. Two of the five cloned repeats contained an insertion of a 195-bp element that is also present at many other sites in the genomes of everyS. purpuratus individual studied. Pairwise comparisons of the different clones indicate that the variation is not uniformly divergent, but ranges from a difference of 0.34% to 3.0% of all nucleotide sites. A parsimonious tree of ancestry constructed from the pariwise comparisons indicates that recombination between the most distantly related repeats has not occurred in the 1–2 million years necessary for accumulation of the variation. The level of sequence variation found within theS. purpuratus population, for both tandemly repeated and single-copy genes, is 25%–50% of that found betweenS. purpuratus andS. drobachiensis.     

树鼩(Tupaia belangeri chinensis)的繁殖

本文讨论了40对树鼩笼养条件下的繁殖。雌雄1:1配对饲养,受孕率为58.1％,每窝产仔2—6只,平均3.48±0.8只,初生幼仔体重均值为10.30±1.2克,35日龄断奶体重均值为59.1±17.6克。正常怀孕期41—45天。在半人工哺乳情况下,新生儿的成活率为74.3％。在与某些灵长类资料比较后,我们认为,树鼩的繁殖特性与灵长类有别。     

Species number, species abundance and body length relationships of arboreal beetles in Bornean lowland rain forest trees

ABSTRACT.

• 1 The relationships between number of species, abundance per species, and body length are examined for 859 species of beetles in samples of arthropods collected from ten Bornean lowland forest trees by insecticide fogging. Similar relationships are examined for different feeding guilds of these beetles, and for those beetles from different species of trees.
• 2 The data are used to construct four interrelated graphs, namely species: abundance, species: body length, population abundance: body length and total number of individuals: body length distributions.
• 3 In contrast to a number of previous studies, no consistent linear relationship between population density and body length was found for the Bornean beetles and it is suggested that, as in birds, the added dispersal ability of flight reduces critical population densities necessary for persistence in small species. Previous relationships between body weight and population abundance may also be artefacts of the way in which data were gathered.
• 4 Despite large samples, we failed to locate the mode in plots of the number of species in each abundance category (species: abundance distribution).
• 5 Species: body length and total number of individuals: body length plots were similar to those found in previous studies, although using data for Coleoptera alone may have produced a steeper decline in the total number of individuals as body size increases than is apparent in samples of all arthropods.
• 6 We present the first three-dimensional graph relating numbers of species, body lengths and population abundances. The surface of this three-dimensional relationship is relatively simple.

     

分子进化研究中的今祖法,其理论基础、存在的问题和解释

在分子进化树的建立上,今祖法(Present-Day Ancestor Method)由于能够避免由于不同进化枝进化速率的不同所造成的错误,对于相距较远的各类群低等生物的进化关系的研究有着特别重要的意义。但是在应用此法于具体的研究时,也遇到了一些令人困惑的带根本性的问题。为此我们对它的理论基础、适用范围和所遇到的问题等等进行了一番认真的考察,并对存在的问题给予了合理的说明。     

Dinoflagellates in evolution. A molecular phylogenetic analysis of large subunit ribosomal RNA

Summary The sequence of the large subunit ribosomal RNA (LsuRNA) gene of the dinoflagellateProrocentrum micans has been determined. The inferred rRNA sequence [3408 nucleotides (nt)] is presented in its most probable secondary structure based on compensatory mutations, energy, and conservation criteria. No introns have been found but a hidden break is present in the second variable domain, 690 nt from the 5 end, as judged by agarose gel electrophoresis and primer extension experiments.Prorocentrum micans LsuRNA length and G+C content are close to those of ciliates and yeast. The conserved portions of the molecule (1900 nt) have been aligned with corresponding sequences from various eukaryotes, including five protista, one metaphyta, and three metazoa. An extensive phylogenetic study was performed, comparing two phenetic methods (neighbor joining on difference matrix, and Fitch and Margoliash on Knuc values matrix) and one cladistic (parsimony). The three methods led to similar tree topologies, except for the emergence of yeast that groups with ciliates and dinoflagellates when phenetic methods are used, but emerges later in the most parsimonious tree. This discrepancy was checked by statistical analyses on reduced trees (limited to four species) inferred using parsimony and evolutionary parsimony methods. The data support the phenetic tree topologies and a close relationship between dinoflagellates, ciliates, and yeast.