The Passiflora coriacea complex encompasses the species P. megacoriacea K.Port.-Utl., P. coriacea Juss and P. sexocellata Schltdl, and the morphological similarities among the species have posed challenges for taxonomic and phylogenetic studies in the past. Image cytometry (ICM) has been used to improve the karyotype characterization in some plant species and has allowed the identification of small variations in the DNA content between homomorphic chromosomes. The aim of the present study was to determine the chromosome number, characterize the karyotype and measure the chromosomal DNA content in P. megacoriacea using classical cytogenetic and ICM approaches. We observed a chromosome number of 2n=12, with the chromosomes 1-3 and 5 classified as submetacentric and chromosomes 4 and 6 as metacentric in all metaphase plates. The nuclear DNA content (1C= 0.51 pg) was measured by flow cytometry and then distributed proportionally to mean integrated optical density values calculated by ICM from Feulgen stained chromosomes. So, the mean 1C chromosomal DNA content varied of 0.129 pg for chromosome 1 to 0.054 pg for chromosome 6. We can thus establish that the ensemble analysis of qualitative and quantitative parameters allowed us the first karyotype characterization of P. megacoriacea, providing data to a better taxonomic delimitation among the species of the P. coriacea Juss complex.
South Brazilian grasslands are among the most species-rich grasslands worldwide yet they have been suffering ongoing degradation due to land-use. Little is known about the reproductive ecology of the native species of these grasslands. Thus, our goal was to characterize seed traits and germination requirements of three native species of the tribe Tigridieae (Iridaceae, Iridoideae) due to its richness in the Pampa biome and the contrasting morphology, cytogenetics, and geographic distributions of its representatives. We tested if closely related species possess similar seed traits and whether species with wider distributions have broader germination requirements. Seed production and mass were estimated, and morphological analyses, germination experiments and viability tests were performed. Principal component analysis (PCA) was used to describe correlations between seed traits and species' distributions. Germination was assessed using time-to-event analysis and the Cox model. All seed traits differed among the analyzed species/cytotypes. Final germination percentage (FGP) averaged 39.1 % and with overall viability of 89.9 %. Germination tests showed that seeds benefit from negative photoblasty. Species/cytotypes with wider distributions and heavier and larger seeds generally had better germination performances than narrower distributed species/ cytotypes with lighter and smaller seeds.
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