The present work contains C-values for 411 taxa including first values for 308 species not listed previously by Bennett and colleagues. Based on a recent estimate of the global published output of angiosperm DNA C-value data (i.e. 200 first C-value estimates per annum) the present work equals 1.5 years of average global published output; and constitutes over 12 % of the latest 5-year global target set by the Second Plant Genome Size Workshop (see http://www.kew.org/cval/workshopreport.html). Hopefully, the present example will encourage others to unveil further valuable data which otherwise may lie forever unpublished and unavailable for comparative analyses.

Nuclear genome size, as measured by flow cytometry with propidium iodide, was used to investigate the relationships within the genus Tulipa L. (Liliaceae). More than 400 accessions representing 123 taxa from mainly wild-collected plants were investigated. Most species of Tulipa have the same basic chromosome number, 2n = 2x = 24. However, the somatic DNA 2C value (2C) is shown to range from 32 to 69 pg for the diploids. The largest genome contains roughly 3.4 9 10 10 more base pairs than the smallest and has chromosomes that are more than twice as large. These large differences in the amount of nuclear DNA predict that the hybrids, if any arise, are usually sterile. Depending on the size of the total genome, 1 pg amounts to several thousand genes. Moreover, genome sizes are evaluated here in combination with available morphological, geographical, and molecular data. Therefore, the taxonomy proposed here is not a single-character taxonomy based on genome size alone. The genus Tulipa, as here determined, has 87 species, 29 more than accepted by van Raamsdonk et al. [Acta Hort (ISHS) 430:821-828, 1997], but including 25 species that were not available to them. Of these 87 species, 28 were not seen by Hall (The genus Tulipa, The Royal Horticultural Society, London, 1940) in a living state and placed by him in an addendum.Species of the subgenus Clusianae (Baker) Zonn. differ strongly in nuclear DNA content (DNA 2C value), 32 versus 40-68 pg for all other tulips, and are placed here in a separate subgenus. Also Orithyia, the only group with a style and with only 38-39 pg is placed in a separate subgenus. Therefore, all tulips are attributed to four subgenera, Clusianae (Baker) Zonn., Tulipa, Eriostemones Raamsd., and Orithyia (D. Don) Baker and divided further into 12 sections. Seven of the eight series of section Eichleres (A.D. Hall) Raamsd. are now placed in four sections: (1) section Lanatae (Raamsd.) Zonn., mainly confined to species from the Pamir-Alay and including series Lanatae Raamsd., (2) section Multiflorae (Raamsd.) Zonn. (including series Glabrae Raamsd.), (3) section Vinistriatae (Raamsd.) Zonn. (including series Undulatae Raamsd.), and (4) section Spiranthera Vved. ex Zonn. and Veldk. Triploids, tetraploids, and pentaploids were found in several species. DNA content confirmed the close relationships of the species within the different sections. The rather similar looking and therefore often confused T. armena Boiss.

The taxonomy of all species of Narcissus (Amaryllidaceae), an important horticultural crop, has not been investigated recently. As a new approach, genome size was determined by flow cytometry with propidium iodide from 375 accessions. The somatic nuclear DNA contents (2C) were shown to range from 14 to 38 pg for the diploids. Narcissus assoanus and N. gaditanus are, based on their nuclear DNA content, removed from section Apodanthi and placed in a new section Juncifolii. The different ploidy levels and species involved were entangled for N. ''fernandesii'' s.l. and a new allotetraploid form is named here. Section Pseudonarcissus was much more heterogeneous in nuclear DNA content than expected. Sixty-five accessions of N. pseudonarcissus possessed, with 23.7 pg, similar amounts of DNA. However, several species from this section were clearly distinctive in nuclear DNA content. It runs from the diploid N. primigenius with 21.7 pg to the also diploid N. nevadensis with 38.2 pg. Also N. abscissus and N. moleroi are with about 26 pg clearly different from N. pseudonarcissus. For the first time, in 11 accessions, hexaploidy was found in N. pseudonarcissus ssp. bicolor. A new section Nevadensis with 30-39 pg of nuclear DNA was split off from the section Pseudonarcissus with now 21-27 pg. A nonoploid N. dubius with 96.3 pg has by far the highest amount of nuclear DNA and can be calculated to have the highest ploidy ever reported in Narcisssus. The total number of Narcissus species was determined as 36, nine more than in Flora Europaea and they were divided up in two subgenera and 11 sections. Flow cytometry is shown to produce easily obtainable and original systematic data that lead to new insights. Genome size or C-value turns out to be one of the most salient features to define the status of the species in the genus Narcissus.

Genome size (C values) and pollen viability staining were applied as new criteria to investigate the taxonomy of the genus Hosta Tratt. (Hostaceae). Nearly all species of the genus Hosta have the same basic chromosome number (2n = 2x = 60). However, the nuclear DNA contents, as measured by flow cytometry with propidium iodide, could be demonstrated to range between 17.2 to 26.6 pg. This implies that the largest genome contains roughly 1010 more base pairs than the smallest. Therefore, nuclear DNA content is a very relevant taxonomic trait that can be measured simply by flow cytometry. In addition, differences in overall DNA composition were demonstrated by comparing to DAPI fluorescence. In general, genome size data confirmed the division into three subgenera. The geographical distribution of genome sizes indicates the migration pattern of Hosta throughout East Asia. The species belonging to the mainly Korean subgenus Bryocles, with a low nuclear DNA content (17.2 ‐ 19.3 pg), can now largely be distinguished from the mainly Japanese species of the subgenus Giboshi (21.3 ‐ 26.5 pg). The exception is H. longissima, that with only 19.6 pg provides a nice example of a decrease in DNA content. On the mainland, as well as on Honshu, species with increased and decreased DNA content have evolved independently. The usefulness of pollen viability to detect hybrids in Hosta was demonstrated in a large series of artificial crosses between bona fide species. Consequently, pollen viability was measured in all available Hosta described as species. Several had low pollen viability and were concluded to be hybrids. Morphology and DNA content confirmed this in most cases. The resulting 23 species approximate the number of Hosta species that follows from the combined studies by Fujita (197618) on the Japanese species and Chung (1991 a11) on the Korean species.

Nuclear genome size of conifers as measured by fl ow cytometry with propidium iodide was investigated, striving to collect at least a single species from each genus. 64 out of 67 genera and 172 species were measured. Of the 67 genera, 21 are reported here for the fi rst time and the same is true for 76 species. Th is nearly doubles the number of measured genera and adds 50% to the number of analyzed species. Conifers have chromosome numbers in the range of n ϭ (7)10 -12(19). However, the nuclear DNA content (2C-value) is shown here to range from 8.3 to 71.6 picogram. Th e largest genome contains roughly 6 ϫ 10 10 more base pairs than the smallest genome. Genome sizes are evaluated and compared with available taxonomic treatments. For the mainly (sub)tropical Podocarpaceae small genome sizes were found with a 2C-value of only 8 -28 pg, with 13.5 pg on average. For the Taxaceae 2C-values from 23 -60 pg were determined. Not surprisingly, the genus Pinus with 97 species (39 species measured here) has a broad range with 2C ϭ 38 -72 pg. A factor of 2 difference is also found in the Cupressaceae (136 species) with nuclear DNA contents in the range 18 -35 pg. Apart from the allohexaploid Sequoia , ploidy plays a role only in Juniperus and some new polyploids are found. Th e data on genome size support conclusions on phylogenetic relationships obtained by DNA sequencing. Flow cytometry is applicable even to young plants or seeds for the monitoring of trade in endangered species.

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This paper presents the largest genome sizes reported so far for angiosperms: for the monocots Trillium hagae (Melanthiaceae)  pg and for the eudicots Viscum album (Santalaceae) with  pg. They were found during ongoing measurements of nuclear DNA content in more than 4000 accessions. Moreover, it is demonstrated that both of the values for the largest genome size so far for the monocots of Fritillaria assyriaca and for the eudicots of Viscum cruciatum need to be corrected.