Morphological variation of Lactuca serriola L. achenes as a function of their geographic origin

The morphological characteristics of achenes of Lactuca serriola represented by 34 local populations from Slovenia and 12 local populations from Sweden were studied in relation to their eco- geographical conditions. In total, eight quantitative morphological characters were evaluated: length and width of achene body; index length/width of achene body; number of ribs on achene body; length of beak; length of pappus bristles; pappus area and discus diameter. NestedANOVAanalysis indicated significant differences in length and width of achene body, length of pappus bristles, and pappus area between Slovenian and Swedish populations. Achenes from Slovenia were longer, wider and possessed longer pappus bristles than achenes from Sweden. Among geographical factors, latitude had the greatest impact on the morphological characters evaluated. Significant differences in seven parameters were also found between populations within countries and between samples within populations. It is probable that this variation has a genetic basis with sufficient variation within populations to permit continued selection

Reintroduction of plant species: S(h)ifting settings.

The aim of this thesis is to contribute tot the knowledge about several temporal and spatial community processes related to the reintroduction of plant species in nature reserves. Such knowledge is necessary to answer questions about the necessity of the feasibility of reintroduction. ... Zie: Summary

Dispersal distance and achene quality of the rare anemochorous species Arnica montana L.:implications for conservation

In The Netherlands, Arnica montana (Asteraceae) is a, rare plant species. Future survival in The Netherlands depends on its; ability to disperse between source populations and habitats, newly created by man. Plumed Asteraceae achenes are often considered to disperse over large distances. Therefore, these species are expected to establish easily during vegetation restoration. In this paper, the flying capability of:plumed achenes is investigated in a wind-tunnel experiment. An effort is made to establish the correlation between seed quality and flying ability. It was shown that A. montana achenes are inefficient dispersers. Pappus size is significantly, but weakly, positively correlated with achene mass. Heavier achenes, therefore, stay closer to the point of release than lighter ones. There was a positive correlation between achene weight and both germination and seedling quality. Consequently, germination and seedling quality declined considerably with increasing flying capability of the achenes. It seems that A. montana, despite its plumed achenes, is adapted to an environment where moderate dispersal distances are required, up to several metres. Only low-quality achenes reach larger distances. Since large distance dispersal is a prerequisite of establishment of new populations, establishment of this species on isolated sites the Dutch landscape will depend on transport by human activity