Comparative embryology of threeGentianaceae species from the Central Caucasus and the European Alps

A comparative investigation was carried out on the ovule and seed development of three mountain species ofGentianaceae, the perennial speciesGentiana pyrenaica, and the two short-lived monocarpic speciesGentianella caucasea andG. germanica. In all three species most embryological characters conform to those generally found in the family of theGentianaceae. In some features, however,G. pyrenaica and the twoGentianella species differ from each other. InG. pyrenaica the ovule is anatropous, the integument 8–10 layered and the three reduced antipodals degenerate soon after fertilization. In contrast,G. caucasea andG. germanica form a hemitropous ovule, a 4–5 layered integument and up to 16 antipodal cells by secondary multiplication. All three species exhibit differences in synchronization between embryogenesis and endosperm development. Functional relations between the antipodal structure and the dynamics of seed development of the investigated species are postulated.     

Differences in the life histories of twoCochlearia species

Cochlearia bavarica Vogt andC. pyrenaica Dc. are closely related and highly endangered species in Bavaria (SE Germany).Cochlearia bavarica (2n=36) is a hybrid ofC. pyrenaica (2n=12) andC. officianalis (2n=24) stabilized by polyploidy.Cochlearia officinalis does not occur in Bavaria. The question being addressed is whether the present non-overlapping distribution of the two Bavarian species, both of which are restricted to calcareous springs with a continuous water supply or drainage ditches, is due to competitive exclusion or to subtle differences of ecological requirements. I did not find any evidence for the second case, i.e. niche differentiation, because both species occurred in all the habitat types that I could define by floristic and ecological criteria. The population structures of bothC. bavarica andC. pyrenaica vary in parallel with different habitat types. Both species have the greatest reproductive output (viable seeds) and the highest population densities in habitats with high light availability and/or low interspecific competition. Thus, I expected that one of the two species might be competitively superior over the other, but that it would fail to reach all its potential sites of occurrence. Cochlearia bavarica individuals (dry mass =5.75 g) grow significantly larger thanC. pyrenaica individuals (3.62 g;P<0.05) and produce more, larger and heavier seeds, possibly due to hybrid vigour. Flowering individuals ofC. bavarica also allocate more biomass to vegetative structures thanC. pyrenaica. The analysis of population dynamics reveals a higher life expectancy and reproductive output inC. bavarica. The calculated population growth rates although negative over the observation period in both species, suggest a significantly higher fitness ofC. bavarica (λ=0.66) compared withC. pyrenaica (λ=0.44). Thus, our data are in line with the competitive exclusion hypothesis andCochlearia bavarica appears as an example of a species with hybridogenous origin possessing higher fitness than its progenitor. However, considering the rarity of both species it seems at present unlikely that the former will displace the latter over a large distributional region.     

Polyphyletic allopolyploid origin ofRanunculus cantoniensis (4x) fromR. silerifolius (2x) ×R. chinensis (2x)

Both diploid and tetraploid experimental interspecific hybrids betweenRanunculus silerifolius (2x) andR. chinensis (2x) exhibit normal bivalent pairing. However, microspores of diploid hybrids do not undergo mitosis and their pollen grains are highly sterile, whereas tetraploid hybrids form good pollen grains after microspore division. Evidence is forwarded for the assumption thatR. cantoniensis (4x) has originated by hybridization between these two diploid parental species and by polyploidization of the diploid hybrids. Parallelisms between the different karyotypes ofR. cantoniensis (4x) andR. silerifolius (2x) suggest that the former is a species of polyphyletic origin.     

Genetic differentiation and speciation in prealpine Cochlearia: Allohexaploid Cochlearia bavarica Vogt (Brassicaceae) compared to its diploid ancestor Cochlearia pyrenaica DC. in Germany and Austria

 Significant geographic partitioning of genetic variation within Cochlearia bavarica was found within populations from Allg?u and SE Bavaria (Germany) exhibiting significant genetic differentiation. It has been demonstrated that allohexaploid C. bavarica evolved via hybridization between diploid C. pyrenaica and tetraploid C. officinalis. Presently, only C. pyrenaica is distributed throughout inland Central Europe. It has been concluded that C. bavarica is of inter- or postglacial origin, and its speciation was not influenced by human activities. Isozyme analysis revealed that there is a correlation between interpopulational genetic distances and geographic distances among C. bavarica populations from both regions, and which is not the case for C. pyrenaica in Germany and Austria. Only high alpine C. excelsa is significantly differentiated among the diploid taxa analysed here. Geographically structured distribution of alleles and their frequencies in C. bavarica populations could not be explained with the distribution of these alleles in C. pyrenaica. The presented findings favour disruption of a former wider distribution area rather than migration of C. bavarica or a polytopic origin of this species. Received April 17, 2001 Accepted February 1, 2002     

Differential responses of three fungal species to environmental factors and their role in the mycorrhization of<Emphasis Type="Italic"> Pinus radiata</Emphasis> D. Don

Three ectomycorrhizal (ECM) isolates of Rhizopogon luteolus, R. roseolus and Scleroderma citrinum were found to differ markedly in their in vitro tolerance to adverse conditions limiting fungal growth, i.e. water availability, pH and heavy metal pollution. S. citrinum was the most sensitive, R. luteolus intermediate and R. roseolus the most tolerant species. Pinus radiata D. Don seedlings were inoculated in the laboratory and in a containerised seedling nursery with spore suspensions of the three ECM species. Colonisation percentage was considerably lower under nursery conditions, probably due to competition by native fungi. The effects of nursery ECM inoculation on seedling growth depended on the fungal species. Only R. roseolus-colonised plants showed a significantly higher shoot growth than non-mycorrhizal plants. All three fungi induced significantly higher root dry weights relative to control plants. Despite the low mycorrhizal colonisation, mycorrhization with all three species improved the physiological status of nursery-grown seedlings, e.g. enhanced root enzyme activity, shoot nutrient and pigment content, net photosynthesis rate and water use efficiency. Of the three fungal species, R. roseolus was the most effective; this species was also the most adaptable and showed the greatest range of tolerance to adverse environmental conditions in pure culture. It is, therefore, proposed as a promising fungal species for ECM inoculation of P. radiata in the nursery.     

Cytotaxonomy of the genusPolystichum in the Western Himalayas

Cytotaxonomical investigations on 11 species from the Western Himalayas show that 8 are diploid and the remaining tetraploid. The numbers for three species are new.P. prescottianum (2x) andP. thomsoni (4x), andP. stimulans (2x) andP. acanthophyllum (4x) are closely related but distinct species pairs.     

Distribution of 5S and 18S–28S rDNA loci in a tetraploid cotton (Gossypium hirsutum L.) and its putative diploid ancestors

The most widely cultivated species of cotton,Gossypium hirsutum, is a disomic tetraploid (2n=4x=52). It has been proposed previously that extant A- and D-genome species are most closely related to the diploid progenitors of the tetraploid. We used fluorescent in situ hybridization (FISH) to determine the distribution of 5S and 18S-28S rDNA loci in the A-genome speciesG. herbaceum andG. arboreum, the D-genome speciesG. raimondii andG. thurberi, and the AD tetraploidG. hirsutum. High signal-to-noise, single-label FISH was used to enumerate rDNA loci, and simultaneous, dual-label FISH was used to determine the syntenic relationships of 5S rDNA loci relative to 18S–28S rDNA loci. These techniques provided greater sensitivity than our previous methods and permitted detection of six newG. hirsutum 18S–28S rDNA loci, bringing the total number of observed loci to 11. Differences in the intensity of the hybrizization signal at these loci allowed us to designate them as major, intermediate, or minor 18–28S loci. Using genomic painting with labeled A-genome DNA, five 18S–28S loci were localized to theG. hirsutum A-subgenome and six to the D-subgenome. Four of the 11 18S–28S rDNA loci inG. hirsutum could not be accounted for in its presumed diploid progenitors, as both A-genome species has three loci and both D-genome species had four.G. hirsutum has two 5S rDNA loci, both of which are syntenic to major 18S–28S rDNA loci. All four of the diploid genomes wer examined contained a single 5S locus. InG. herbaceum (A₁) andG. thurberi (D₁), the 5S locus is syntenic to a major 18S–28S locus, but inG. arboreum (A₂) andG. raimondii (D₅), the proposed D-genome progenitor ofG. hirsutum, the 5S loci are syntenic tominor and intermediate 18S–28S loci, respecitively. The multiplicity, variation in size and site number, and lack of additivity between the tetraploid species and its putative diploid ancestors indicate that the behavior of rDNA loci in cotton is nondogmatic, and considerably more complex and dynamic than previously envisioned. The relative variability of 18S–28S rDNA loci versus 5S rDNA loci suggests that the behavior of tandem repearts can differ widely. Edited by: R. Appels     

Restriction fragment length polymorphisms in the genusActinidia (Actinidiaceae)

A series of chloroplast and nuclear probes were used to examine restriction fragment length polymorphisms (RFLPs) in kiwifruit (Actinidia deliciosa) and three of its closest relatives. The four species fell into two pairs, withA. chinensis andA. deliciosa closely related but some distance away from the other two species,A. latifolia andA. eriantha. The results are consistent with the hypothesis that the diploid species,A. chinensis, is a precursor ofA. deliciosa, which is hexaploid.     

Karyomorphological studies onWoodwardia sensu lato of Japan

Karyomorphological comparisons were made of five species of JapaneseWoodwardia. There were no marked differences at interphase and prophase among the five species.Woodwardia japonica, W. prolifera, andW. unigemmata were diploid with 2n=68 and the formulas of their metaphase karyotypes uniformly 4m(median centromeric chromosomes)+12sm(submedian)+52(st+t)(subterminal and terminal).Woodwardia orientalis was tetraploid with 2n=136 and 8m+24sm+104(st+t), and the ratio of each chromosomal type to total complement was identical to that of three diploid species. These four species had several characteristics in common:x=34, the longest chromosome of sm, and a mean chromosome length over 3.0 μm. AlthoughWoodwardia orientalis showed some similarity toW. prolifera, it seems to be an allotetraploid which originated by chromosome doubling of a hybrid ofW. prolifera and a diploid species as yet karyomorphologically unknown.Woodwardia kempii was tetraploid with 2n=124 and 8m+24sm+92(st+t), and differed from the others in havingx=31, the longest chromosomes of t, and a mean chromosome length under 3.0 μm. This species has been classified as an independent genus,Chieniopteris, and our karyomorphological study supports this treatment.     

Forest Management and Plant Species Diversity in Chestnut Stands of Three Mediterranean Areas

Over many centuries, chestnut fruits had an important role as food, while chestnut wood was used for local purposes. Today sweet chestnut stands are very common around the western Mediterranean Basin, and it is necessary to analyze the dynamic of plant species diversity in different chestnut stand types (groves and coppices) to guide management strategies that will allow the conservation of biodiversity. Our objective was to analyze consequences on plant species diversity of various management strategies in chestnut stands of three Mediterranean areas, Salamanca (Spain), the Cévennes (France), and Etna volcano (Italy). We found that plant species diversity is different according to management types; it is higher in groves than in coppice stands. We also demonstrated that Castanea sativa cultivated groves were characterized by small heliophillous therophytes. C. sativa abandoned groves, mixed C. sativa–Quercus pyrenaica coppice stands, Q. pyrenaica coppice stands, and young C. sativa coppice stands were characterized by hemicryptophytes with anemochorous dispersal mode and chamaephytes. Medium and old C. sativa coppice stands (that differ by the shoot age) were characterized by phanerophytes with zoochorous dispersal mode. Human perturbations maintain a quite high level of species diversity. In contrast, the abandonment of chestnut stands leads to homogeneous vegetation with decreasing diversity. One solution could be to maintain a landscape mosaic constituted of diverse chestnut stands modified by human activities (groves, cultivated or abandoned, and coppice stands). This could enhance regional plant diversity.     

Genetic variation and conservation of Changnienia amoena, an endangered orchid endemic to China

Nuclear DNA content (2C) is used as a new criterion to investigate nearly all species of the genus Nerine Herb. The species have the same chromosome number (2n = 2x = 22), with the exception of three triploid plants found. The nuclear DNA content of the diploids, as measured by flow cytometry with propidium iodide, is demonstrated to range from 18.0–35.3 pg. This implies that the largest genome contains roughly 2 × 10¹⁰ more base pairs than the smallest. The species, arranged according to increasing genome size, fell apart in three groups if growth cycle and leaf width were also considered. A narrow-leafed, evergreen group with a DNA content between 18.0 and 24.6 pg contains thirteen species, a broad-leaved winter growing group with four species has a DNA content from 25.3–26.2 pg and a broad-leafed summer growing group has a DNA content of 26.8–35.3 pg and contains six species. If the presence of filament appendages and hairiness of the pedicels were also considered, the thirteen evergreen species could be further divided into a group without filament appendages or hairy pedicels with a DNA content of 18.0–18.7 pg. A second group without filament appendages but with hairy pedicels had a DNA content of 19.7–22.3 pg. And a third group with both filament appendages and hairy pedicels had a DNA content of 22.0–24.6 pg. The exception is N. marincowitzii that, despite a low DNA content and narrow leaves is summer growing. The broad-leafed group is further characterised by the absence of filament appendages and the absence of strongly hairy pedicels. The exception here is N. pusilla that, despite a high DNA content, has narrow leaves and minutely hairy pedicels. Nuclear DNA content as measured by flow cytometry is shown to be relevant to throw new light on the relationships between Nerine species.     

Chromosome numbers, karyotypes and nuclear DNA contents from perennial polyploid groups ofCerastium (Caryophyllaceae)

Somatic chromosome numbers have been determined for the followingCerastium taxa:C. eriophorum (2n = 36),C. alpinum (2n = 72),C. transsylvanicum (2n = 108),C. arcticum (2n = 108),C. latifolium (2n = 36),C. carinthiacum (2n = 36),C. banaticum (2n = 36),C. arvense subsp.glandulosum (2n = 36),C. arvense subsp.arvense (2n = 72) andC. fontanum (2n = 144). Karyotypes of three diploid species (C. eriophorum, C. banaticum andC. latifolium), belonging to three different taxonomic groups, were analysed and found to be similar. The relative nuclear DNA contents of all taxa were determined by flow cytometry and, for five species, also by Feulgen cytophotometry. The values obtained by the two methods are similar. A comparison of nuclear DNA contents among diploids shows that values differ significantly between different taxonomic groups, and are correlated with average chromosome size. Within closely related polyploid groups nuclear DNA amounts increase from 2x- to 4x- and 6x taxa as 1 : 1.4 : 2.4 in theC. alpinum complex, whereas DNA amounts are doubled comparing 2x- and 4x-subspecies in theC. arvense complex.     

Light response in seedlings of a temperate (<Emphasis Type="Italic">Quercus petraea</Emphasis>) and a sub-Mediterranean species (<Emphasis Type="Italic">Quercus pyrenaica</Emphasis>): contrasting ecological strategies as potential keys to regeneration performance in mixed marginal populations

In order to understand better the ecology of the temperate species Quercus petraea and the sub-Mediterranean species Quercus pyrenaica, two deciduous oaks, seedlings were raised in two contrasting light environments (SH, 5.3% full sunlight vs. HL, 70% full sunlight) for 2 years, and a subset of the SH seedlings were transferred to HL (SH–HL) in the summer of the second year. We predicted that Q. pyrenaica would behave more as a stress-tolerant species, with lower specific leaf area (SLA), allocation to leaf mass, and growth rate and less responsiveness to light in these metrics, than Q. petraea, presumed to be more competitive when resources, especially light and water, are abundant. Seedlings of Q. petraea had larger leaves with higher SLA, and exhibited a greater relative growth rate (RGR) in both SH and HL. They also displayed a higher proportion of biomass in stems (SMF), and a lower root to shoot ratio (R/S) in HL than those of Q. pyrenaica, which sprouted profusely, and had higher rates of photosynthesis (A_n) and stomatal conductance (g_wv), but lower whole-plant net assimilation rate (NAR). On exposure to a sudden increase in light, SH–HL seedlings of both species showed a short period of photoinhibition, but fully acclimated photosynthetic features within 46 days after transference; height, main stem diameter, RGR and NAR all increased at the end of the experiment compared to SH seedlings, with these increases more pronounced in Q. petraea. Observed differences in traits and responses to light confirmed a contrasting ecology at the seedling stage in Q. petraea and Q. pyrenaica in consonance with differences in their overall distribution. We discuss how the characteristics of Q. petraea may limit the availability of suitable regeneration niches to microsites of high-resource availability in marginal populations of Mediterranean climate, with potential negative consequences for its recruitment under predicted climatic changes.     

Three species groups in American trilliums as revealed by compatibility with an Asian species

American trilliums are all diploid and are classified into three groups with regard to compatibility withTrillium kamtschaticum, a single diploid Asian species: (1) Compatible pedicellate-flowered species, i.e.T. erectum, T. gleasoni, andT. vaseyi. (2) Incompatible pedicellate-flowered species, i.e.T. grandiflorum. (3) Incompatible sessile-flowered species, i.e.T. decunbens, T. luteum, T. sessile andT. stamineum. HybridsT. kamtschaticum×T. erectum flowered for the first time 9–10 years after sowing F₁ seeds. The F₁ were completely sterile in pollen and in seed-setting.     

Relative rate of development of aneuploid cells in an euploid environment

The relative rate of development of aneuploid and eudiploid microspores was studied in anthers of autotetraploidTradescantia virginiana (4x=24), Lycopersicum esculentum (4x=48) andSecale cereale (4x=28). Although the species showed slight differences, in all three the first pollen grain mitosis took place considerably later in aneuploid than in euploid cells. Although hypoploid cells were somewhat more retarded than hyperploid cells, the difference was not great, indicating a decidedly lower degree of developmental autonomy of microspores than of embryos, which only infrequently tolerate hypoploidy at the diploid level.     

Physical mapping of ribosomal DNA on several species of the subgenus Rosa

The localization of NORs by fluorescent in situ hybridization on metaphase spreads of five diploid (Rosa gigantea Coll., Rosa moschata Herrm., Rosa multiflora Thunb., Rosa rugosa Thunb. and Rosa sempervirens L., 2n=2x=14), one triploid (Rosa chinensis’semperflorens’ Koehne., 2n=3x=21) and one tetraploid (Rosa gallica ’versicolor’ L., 2n=4x=28) ancestral species of modern roses was studied. Two terminal hybridization signals were observed in all diploid species corresponding to a single NOR per genome in these species. Triploid R. chinensis showed three hybridization sites on the short arm of three morphologically similar chromosomes. Six hybridization sites, located at terminal positions of the short arms of three chromosome pairs, were observed in the tetraploid species. These signals corresponded to three pairs of NORs and all of them were located in chromosome pairs of different size. These observations, together with the analysis of meiotic pairing in PMCs, support the view that our specimen of R. chinensis is an autotriploid and that R. gallica’versicolor’ has an alloploidy nature. Received: 27 November 2000 / Accepted: 12 March 2001     

Karyological studies on Indian spiders

The diploid set of chromosomes inPalystes whiteae Pocock (Eusparassidae),Selenops montigenus Simon (Selenopidae) andTarrocanus viridis Dyal (Thomisidae) is constituted by forty-three, twenty-nine and twenty-seven acrocentric elements respectively. The males of all these three species have a sex-determining mechanism of the XXXO-type. The autosomes ofP. whiteae andT. viridis are simple rods, more or less pointed at one end, while inS. montigenus they carry terminal knobs. The sex-chromosomes which are unequal, move to one pole of the spindle precociously, during anaphase I.     

Ecological wood anatomy of NepaleseRhododendron (Ericaceae). 2. Intraspecific variation

The intraspecific relationship of selected wood anatomical characters with stem diameter, plant height, and altitude was investigated in four NepaleseRhododendron species:R. anthopogon, R. lepidotum, R. campanulatum, andR. arboreum, i.e., two shrubs, one subtree, and one tree. We studied 23 to 27 specimens for each species.R. anthopogon grew from 3,380 to 4,950 m,R. lepidotum from 2,060 to 4,720 m,R. campanulatum from 2,790 to 4,140 m, andR. arboreum from 1,430 to 3,460 m. Multiple regression analysis and actual distribution of character values show that the wood anatomical characters having a significant correlation with non-anatomical factors differ between species. The number of significant characters are two inR. anthopogon andR. campanulatum, five inR. lepidotum, and nine inR. arboreum and tends to be small in species having smaller altitudinal ranges. Average pore area, most strongly correlated with non-anatomical factors in interspecific variation, is significantly correlated only inR. lepidotum andR. arboreum. The general trends in intraspecific variation among four NepaleseRhododendron species differ from the trends found in interspecific variation within the genus and are characteristic of each species.     

Trigonotis jiaochengensis sp. nov. (Boraginaceae) from Shanxi,China

Trigonotis jiaochengensis Q. R. Liu & R. Y. Yan, a new species from Shanxi, China, is described and illustrated here. It is similar to T. peduncularis in having multiple diffuse stems, ovate to elliptic leaf blades, scorpioid cyme with only basal bracts and trigonous‐tetrahedral nutlets, but differs in having slender pedicels that are 5.2–18.4 mm long (vs clavate pedicels 1.5–4.8 mm in T. peduncularis), smooth nutlets with a short carpophore and a flat bottom (vs verrucose nutlets with a long carpophore and convex bottom in T. peduncularis). Morphological characters, including pollen and nutlets, with illustrations, diagnostic comparisons and habitat, are presented.     

Morphological and molecular characterisation confirm that Triticum monococcum s.s. is resistant to wheat leaf rust

The three diploid wheat species Triticum monococcum, Triticum boeoticum and Triticum urartu differ in their reaction to wheat leaf rust, Puccinia triticina. In general, T. monococcum is resistant while T. boeoticum and T. urartu are susceptible. However, upon screening a large collection of diploid wheat accessions, 1% resistant T. boeoticum accessions and 16% susceptible T. monococcum accessions were found. In the present study these atypical accessions were compared with 49 typical T. monococcum, T. boeoticum and T. urartu accessions to gain insight into the host-status of the diploid wheat species for wheat leaf rust. Cluster analysis of morphological data and AFLP fingerprints of the typical accessions clearly discriminated the three diploid species. T. monococcum and T. boeoticum had rather-similar AFLP fingerprints while T. urartu had a very different fingerprint. The clustering of most atypical accessions was not consistent with the species they were assigned to, but intermediate between T. boeoticum and T. monococcum. Only four susceptible T. monococcum accessions were morphologically and moleculary similar to the typical T. monococcum accessions. Results confirmed that T. boeoticum and T. monococcum are closely related but indicate a clear difference in host-status for the wheat leaf rust fungus in these two species. Received: 7 November 2000 / Accepted: 31 March 2001