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Chromosome number, meiotic behavior, and pollen viability were analyzed in 15 species of two genera, Vriesea and Aechmea, native to Rio Grande do Sul, Brazil. This study is the first cytogenetic analysis of these taxa. The chromosome numbers are all n = 25, consistent with the proposed base number of x = 25 for Bromeliaceae. All examined taxa displayed regular bivalent pairing and chromosome segregation at meiosis. Observed meiotic abnormalities include univalents in metaphase I; missing or extra chromosomes and precocious division of centromeres in metaphase II; laggards in telophase I and anaphase II/telophase II. The high pollen viability (>88%) reflects a regular meiosis. Key words: Aechmea; Bromeliaceae; chromosome numbers; meiotic behavior; pollen viability; Vriesea.

This study aimed to evaluate the effects of Schinus terebinthifolius leaf essential oil on adventitious rooting of Arabidopsis thaliana. Effects of the oil were assessed on root formation and elongation of A. thaliana microcuttings. Accumulation of hydrogen peroxide (H2O2), a reactive oxygen species (ROS), in microcuttings and the action of an antioxidant and an auxin in alleviating essential oil effects were assessed. The essential oil reduced mean rooting time and root length of A. thaliana in a dose-dependent manner but did not affect rooting rate or number of roots. Accumulation of H2O2 was evidenced in A. thaliana leaves exposed to the essential oil, which was prevented by addition of the antioxidant. The antioxidant alleviated effects of the oil on A. thaliana, but not the auxin. In conclusion, root elongation was more affected by S. terebinthifolius essential oil than root formation, and phytotoxic effects were associated with oxidative damage. [ABSTRACT FROM AUTHOR]

A remarkable morphological similarity in natural populations of different groups of Sisyrinchium spp. ( Iridaceae) makes classification of some species difficult. The present paper focused on two morphological categories of S. sellowianum ( MC-I and MC-II) with distinct morphological traits. Morphological, cytogenetic, reproductive biology and genetic studies were performed, aiming to elucidate and better characterize such variation. The basic chromosome number established for the species was x = 9 and diploid and tetraploid populations were observed for MC-I, whereas MC-II showed only diploid populations. Different pollen morphologies were recognized in each morphological category. Based on pollination experiments, MC-I is out-crossing, whereas MC-II is selfing. The populations were highly differentiated ( F ST = 0.46, θB = 0.62). In MC-I, observed variation was greater within populations (69%) than among populations (31%), whereas in MC-II, 61% of the variation was among populations and 39% within populations. This study evidenced that the two morphological categories correspond to distinct and reproductively isolated species and that floral traits reflect their breeding system, with allogamous plants in MC-I and autogamous in MC-II. Furthermore, MC-II is unveiled as S. platycaule, a neglected taxon of Sisyrinchium in Brazil. The tools applied in this study were substantially able to check the identity of the two morphological categories as two different species and present the variation encountered in the taxa. [ABSTRACT FROM AUTHOR]

With the present work, we aim to provide a better understanding of chromosome evolutionary trends among southern Brazilian species of Iridoideae. Chromosome numbers and genome sizes were determined for 21 and 22 species belonging to eight genera of Tigridieae and two genera of Trimezieae, respectively. The chromosome numbers of nine species belonging to five genera are reported here for the first time. Analyses of meiotic behaviour, tetrad normality and pollen viability in 14 species revealed regular meiosis and high meiotic indexes and pollen viability (> 90%). The chromosome data obtained here and compiled from the literature were plotted onto a phylogenetic framework to identify major events of chromosome rearrangements across the phylogenetic tree of Iridoideae. Following this approach, we propose that the ancestral base chromosome number for Iridoideae is x = 8 and that polyploidy and dysploidy events have occurred throughout evolution. Despite the variation in chromosome numbers observed in Tigridieae and Trimezieae, for these two tribes our data provide support for an ancestral base number of x = 7, largely conserved in Tigridieae, but a polyploidy event may have occurred prior to the diversification of Trimezieae, giving rise to a base number of x2 = 14 (detected by maximum-parsimony using haploid number and maximum likelihood). In Tigridieae, polyploid cytotypes were commonly observed (2 x, 4 x, 6 x and 8 x), whereas in Trimezieae, dysploidy seems to have been the most important event. This feature is reflected in the genome size, which varied greatly among species of Iridoideae, 4.2-fold in Tigridieae and 1.5-fold in Trimezieae. Although no clear difference was observed among the genome sizes of Tigridieae and Trimezieae, an important distinction was observed between these two tribes and Sisyrinchieae, with the latter possessing the smallest genome sizes in Iridoideae. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 177, 27-49. [ABSTRACT FROM AUTHOR]

Reproductive biology and plant fertility are directly related to many aspects of plant evolution and conservation biology. Vriesea friburgensis is an epiphytic and terrestrial bromeliad endemic to the Brazilian Atlantic rainforest. Hand-pollination experiments were used to examine the reproductive system in a wild population of V. friburgensis. Plant fertility was assigned considering flower production, fruit and seed set, seed germination, and pollen viability. Self-sterility observed from spontaneous selfing and manual self-pollination treatments may be the consequence of late-acting self-incompatibility. Hand-pollination results indicated no pollen limitation in the population studied. Floral biology features such as a few daily open flowers, nectar production, and sugar concentration corroborate hummingbirds as effective pollinators, although bees were also documented as pollinators. Components of fitness such as high flower, fruit, and seed production together with high seed and pollen viability indicate that this wild population is viable. From a conservation point of view, we highlight that this self-sterile species depends on pollinator services to maintain its population fitness and viability through cross-pollination. Currently, pollinators are not limited in this population of V. friburgensis. Conversely, the maintenance and continuous conservation of this community is essential for preserving this plant-pollinator mutualism. [ABSTRACT FROM AUTHOR]

Plant fertility can influence many aspects of population ecology and evolution. The quantity and quality of pollen produced by a plant is an important component of reproductive success. Plant fertility was analyzed by assessing: chromosome number, meiotic behavior and pollen viability of seven native populations of Vriesea gigantea. All plants presented 2n = 50 chromosomes. Most of the pollen mother cells showed a regular meiotic behavior with 25 bivalents and regular chromosome segregation. In accordance, high pollen viability (84–98%) was recorded for all investigated populations. These results indicated that plants from all populations analyzed are fertile. Despite the overall high pollen viability, significant differences were detected among populations. The population of Praia do Araçá showed a reduced percentage of pollen viability, although meiosis was quite regular. Reduction in pollen viability could have an important effect on plants fertility and, consequently, on fitness of this population. [ABSTRACT FROM AUTHOR]

Polyploidy is often related with phenotypic variation, as observed in Herbertia lahue, a geophyte species. This study examined the H. lahue polyploid series and departure in cytogenetic, morphometric, and pollen data. Diploids (2n=2x=14) present bimodal karyotype with two long and five short chromosome pairs, while hexaploids (2n=6x=42) and octoploids (2n=8x=56) present a gradual decrease in chromosome size. All cytotypes have CMA+/DAPI- bands co-localized with 18S rDNA sites in the satellite region (no DAPI+ bands in any cytotype). Unlike diploids and octoploids, 5S rDNA interstitial sites in hexaploids are not in a syntenic position with 18S rDNA sites. Genome size is effective as an indirect predictor of the cytotypes since 2C-values increased according to ploidy level. The reduction in the number of the rDNA sites in polyploids associated with their lower 1Cx-values compared to diploids may suggest a genome downsizing process. Morphometric analysis revealed significant differences among cytotypes, and discriminant analysis identified three morphometric groupings corresponding to the cytotypes. The phenotypic variation observed in pollen grains, bulbs, and ovary characters suggested the gigas effect. Concluding, remarkable differentiation was observed at both genomic and phenotypic characters in all the cytotypes analyzed, suggesting a possible ongoing speciation process in H. lahue.