Sucrose utilization during ovule and seed development ofGasteria verrucosa (Mill.) H. Duval as monitored by sucrose synthase and invertase localization

Summary The development ofGasteria verrucosa ovules and seeds seems to follow a pattern of growth in which the majority of carbohydrates is first used in the sporophytic tissue (nucellus, integuments, and arillus) around the gametophyte-derived cells. After fertilization the carbohydrates are used for further development of the arillus and seed coat. During the next stage carbohydrates are directed to develop the endosperm, followed by carbohydrate investment in the developing embryo and in storage products. This utilization pattern is deducted from a localization study on sucrose synthase and invertase. These two enzymes break down imported sucrose and are in that perspective used as markers for carbohydrate transport since diffusion is expected to be induced towards cells and tissues with high sucrose-hydrolyzing activities.     

Morpho-colorimetric characterization by image analysis to identify diaspores of wild plant species

Digital images of ex situ germplasm stored in the Sardinian Germplasm Bank (BG-SAR) were used for the application of image analysis techniques at the Stazione Sperimentale di Granicoltura per la Sicilia. The analysed accessions refer to 148 taxonomic units belonging to 102 genera and 47 families, typical of the Sardinian flora, and of the Mediterranean basin in general.The images of diaspores were acquired by a flatbed scanner and elaborated with a macro specially developed for the morphometric and colorimetric measurements. This method allowed carrying out a database for the characterization of autochthonous germplasm in entry to the bank and the realization of statistic classifiers for the discrimination of genera and species within the following families: Apiaceae, Boraginaceae, Caryophyllaceae, Cistaceae, Fabaceae and Scrophulariaceae. Such classifiers, based on the linear discriminant analysis (LDA) technique and checked by cross-validation, showed a performance included between 74.3% and 96.4%.In addition, for the genus Astragalus, it was possible to elaborate a classifier able to identify very similar taxa of a species complex, obtaining a performance between 83.7% and 100%. Such analysis proved the validity of the methodology also from the taxonomic point of view.Suggestions for subsequent methodological progress, which could offer applications in other research issues, such as ecological analysis, soil seed bank and archaeological botany are proposed.     

Short-term variability of plant populations within a regularly disturbed habitat

The changing populations of weeds during 13 years of the Broadbalk continuous wheat experiment were analysed to investigate the extent of differences in shortterm variability of cover between species. The data were from two sections of the experiment where winter wheat was grown continuously under herbicide treatment for 13 and 6 years respectively. Logistic regressions were fitted to the data. Equisetum arvense showed significant long-term increases on both sections; long-term trends were also detected in the longer data run for Agrostis stolonifera, Cirsium arvensa, Poa trivialis, Ranunculus arvensis and Vicia sativa, and for Medicago lupulina on the shorter data run. Variation around long-term trends was low in the case of Equisetum, and, in the longer data run, for Cirsium and Tussilago farfara, and high for Poa spp. and Vicia. Cover values on the two sections were positively correlated for Alopecurus myosuroides, Equisetum, Poa annua and Tripleurospermum inodorum. There was a weak correlation between C-S-R strategy and short-term variability; the more competitive species displayed less variability than the ruderal species. Furthermore, species regenerating from persistent seed banks were more variable in the short term than those regenerating from short-lived seed or bud banks. This can be explained by differences in response to year-to-year variation in environmental conditions, those species with persistent seed banks being typically more sensitive to annual fluctuations in the environment than those without.     

Genetic variation of liverleaf (Hepatica nobilis Schreb.) in Bavaria against the background of seed transfer guidelines in forestry and restoration

The liver leaf, Hepatica nobilis (Ranunculaceae), is a perennial forest understory herb with specific habitat requirements, which occurs on calcareous soils in beech and oak forests. In Bavaria it can be found, therefore, only in four geographic regions, which are Franconia, the Franconian-Swabian Jura, the prealpine transitions region and the prealpine moraine belt with the Alps. In German forestry, provenance delineations are used since 1987. Similarly for herbs seed provenances and production areas are applied in commercial seed production and restoration. In this study we analyzed whether the genetic variation of H. nobilis reflects the geographic distribution of the species in Bavaria or the provenance delineations used for seed production.We applied AFLPs to study genetic variation within and between 24 populations of H. nobilis.Our analysis revealed high levels of genetic variation within and moderate variation between populations. Variation between seed production areas and seed provenances was low and comparable to the variation between geographic regions. Genetic variation within populations or rare fragments did not differ between production areas, provenances or geographic regions. A significant positive relation of genetic and geographic distances was present within 100 km.Pollination and seed dispersal seem mainly to happen within populations of the myrmecochorous H. nobilis, whereas long-distance dispersal is presumably occasional and random. Our study supports the relevance of dispersal traits for seed collections used in conservation. The protection of historically old beech and oak forests is exceedingly important to preserve the genetic variation of H. nobilis in Bavaria.     

Biodiversity and ecosystem functioning: It is time for dispersal experiments

The experimental study of the relationship between biodiversity and ecosystem function has mainly addressed the effect of species and number of functional groups. In theory, this approach has mainly focused on how extinction affects function, whereas dispersal limitation of ecosystem function has been rarely discussed. A handful of seed introduction experiments, as well as numerous observations of the effects of long‐distance dispersal of alien species, indicate that ecosystem function may be strongly determined by dispersal limitation at the local, regional and/or global scales. We suggest that it is time to replace biodiversity manipulation experiments, based on random draw of species, with those addressing realistic scenarios of either extinction or dispersal. Experiments disentangling the dispersal limitation of ecosystem function should have to take into account the probability of arrival. The latter is defined as the probability that a propagule of a particular species will arrive at a particular community. Arrival probability depends on the dispersal ability and the number of propagules of a species, the distance a species needs to travel, and the permeability of the matrix landscape. Current databases, in particular those in northwestern and central Europe now enable robust estimation of arrival probability in plant communities. We suggest a general hypothesis claiming that dispersal limitation according to arrival probability will have ecosystem‐level effects different from those arising due to random arrival. This hypothesis may be rendered more region‐, landscape‐ or ecosystem‐specific by estimating arrival probabilities for different background conditions.     

Levels of genetic diversity at different stages of the domestication cycle of interior spruce in British Columbia

Concerns over the reductionist nature of the domestication of forest-tree species focus on the possibility of potential genetic erosion during this process. To address these concerns, genetic diversity assessments in a breeding zone the Province of British Columbia “interior” spruce (Picea glauca×engelmanni) program was conducted using allozyme markers. Genetic-variation comparisons were made between natural and production (seed orchard) populations as well as seed and seedling crops produced from the same breeding zone’s seed orchard. The natural population sample consisted of a total of 360 trees representing three stands within each of three watersheds present in the Shuswap-Adams low-elevation zone of interior British Columbia. Small amounts of genetic differentiation were observed among the nine natural populations (4%) and this was attributable to extensive gene flow Consequently, the sum of these nine populations was considered as a baseline for the genetic variation present in the breeding zone. The comparisons between the seed orchard and the breeding zone produced a similar percentage of polymorphic loci while the expected hetrozygosity (0.207 vs 0.210) and the average number of alleles per locus (2.7 vs 2.4) were slightly lower in the seed orchard. A total of seven natural populations’ rare alleles were not present in the orchard population, while one allele was unique to the orchard. The %P increased to 70.6% in the seedlot, but dropped to the natural populations level (64.7%) in the plantation. The observed increase in %P was a result of pollen contamination in the orchard. It is suspected that the reduction in the plantation was caused by an unintentional selection in the nursery. Simulated roguing in the orchard did not drastically reduce even if up to 50% of the orchard’s clones were rogued. However, roguing was associated with a reduction in the average number of alleles per locus (i.e., sampling effect). Received: 2 January 1996 / Accepted: 24 May 1996     

Seed germination,seedling inoculation and establishment ofAlnus spp. in containers in greenhouse trials

Methods for production of containerized seedlings ofAlnus species were developed which permit nitrogen-fixing nodules to form on the root systems prior to outplanting, in order to provide an early nitrogen input during seedling establishment. The methods are based on procedures for inoculating root systems with suspensions ofFrankia (Actinomycetales), applied either directly in the container cell as a soil drench at the time of seeding, or as a root dip for seedlings transplanted into the containers. Germination of dried, stored seed was enhanced by light and by presoaking for 16 h in water. Pretreatments to overcome seed dormancy or to eliminate fungal pathogens did not further enhance germination. Some loss of seedlings was recorded in the early stages of growth shortly after germination, which is a factor in calculating projected seedling yield. Nodulation and seedling growth were evaluated in terms of growth media characteristics. Seedlings performed well in peat-vermiculite, at soil pH between 5.5 and 8.0.     

Butenolide from plant-derived smoke enhances germination and seedling growth of arable weed species

We tested the applicability of the recently identified major germination cue from smoke (a butenolide 3-methyl-2Hfuro[2,3-c]pyran-2-one) on 18 weed species from non-fire prone environments. For the study species we compared the relative effectiveness of alternating temperatures, KNO₃, GA₃, smoke water and the butenolide on germination percentage, germination rate and seedling mass. We found that while smoke stimulated germination in a number of species it also had negative impacts on other species. In addition, the butenolide was effective on the widest range of species in terms of enhancing germination percentage, rate and seedling mass. However, none of the treatments, including butenolide were effective on all species. Our data demonstrate that butenolide may have wide applicability as a germination and seedling growth stimulant irrespective of whether the species come from fire-prone habitats.     

Germintion,nodulation and early growth response of a hard-seeded legume,Lathyrus sylvestris L. (flatpea)

Summary Flatpea (Lathyrus sylvestris L.) requires seed scarification for rapid germination and specificRhizobium leguminosarum strain for nodulation. Methods of inoculation were investigated to determine which would be effective for at least two weeks after seeding. Application of powdered peat to wet seeds was inadequate. Lime pelleting and granular soil implants were effective inoculants, but there appears to be a different advantage to seedling for earch metod. Granular soil implant caused nodulation to a greater depth on the tap root, and lime pelleting caused plants to exhibit higher acetylene reduction activity.