Brazilian Journal of Botany最新文献

The geographical distribution of a taxon is the result of factors specific to the organisms and the environment in which they live. Similar, repetitive, and non-random occurrence arrangements comprise the distribution patterns. Ferns are a group with a wide range, whose spatial patterns are often associated with spore dispersion and environmental factors. Pteridaceae is the most species-rich fern family in Brazil, present in all phytogeographic Brazilian domains. This study aimed to map the occurrence of all Pteridaceae species in Brazil to verify distribution patterns. The occurrence points of the species were obtained from the review of herbaria, and the patterns were delimited according to the congruence of the limits of species presence, and the range in Brazilian states and the biogeographical provinces. Each taxon’s range was classified as continuous and disjunct; for the first one, some subtypes were also considered: very restricted, restricted, moderately wide, and wide. The presence of 205 species was verified, with natural occurrences for Brazil. Minas Gerais and Rio de Janeiro are the richest states in the number of species, and regarding the provinces, the Atlantic and Paraná Forests are the richest. A total of 123 patterns were defined, 93 (173 species) for continuous, and 30 for disjunct (32 species). Considering the continuous patterns, 18 were classified as very restricted (70 species), 14 as restricted (27 species), 51 as moderately wide (63 species), and 10 as wide (13 species). The Brazilian mountain regions are home to a large number of endemic species (such as Serra do Mar, Serra da Mantiqueira, and the Guiana Shield). Environmental characteristics, such as rock types, humidity, precipitation, and elevation seem to be important for the species’ establishment. Furthermore, the dispersal ability of the spores must be considered, given the range of occurrence of the taxa and the age of the lineages.

Succulents are widely appreciated for indoor decoration, primarily due to their vibrant leaf colors. However, the underlying mechanisms of leaf color development in succulents remain largely unexplored. In this study, we isolated AaMYB4, an MYB transcription factor that represses anthocyanin synthesis, from an ornamental succulent, Aeonium arboreum Webb & Berthel ‘Halloween’. Our study incorporated gene cloning, bioinformatics, functional validation of transgenes, and yeast two-hybrid assays to investigate AaMYB4’s role. The finding revealed that the full-length Open Reading Frame (ORF) of AaMYB4 spans 825 base pairs, encoding 274 amino acids. Bioinformatics analyses suggested that AaMYB4 functions as an R2R3-MYB transcription factor suppressing flavonoid biosynthesis, characterized by a typical repressive EAR motif. Functional validation of transgenes for AaMYB4 indicated that the anthocyanin content was significantly reduced in AaMYB4 overexpressing Arabidopsis compared with the WT under nitrogen deficiency, high light exposure, 6% sucrose, and abscisic acid (ABA) treatment, and the structural genes for anthocyanin synthesis were down-regulated in the AaMYB4 transgenic Arabidopsis. Furthermore, in terms of transcription factors in the AaMYB4 transgenic Arabidopsis, the expression levels of AtPAP1 and AtTT8 exhibited a significant downregulation. Yeast two-hybrid assays revealed no interaction between AaMYB4 and AaTT8, and the AaMYB4 protein can self-interact. This research confirmed the role of AaMYB4 in inhibiting anthocyanin synthesis in ‘Halloween’ leaves, enriching our understanding of the molecular basis of leaf color formation in succulents. Additionally, it offers valuable genetic insights for developing new ‘Halloween’ colorful leaf varieties.

Jasminum L., a genus of Oleaceae, contains different species that are often used in medicinal and industrial fields. Genomic data of Jasminum are essential for elucidating the evolutionary history and mining DNA-based applications. Therefore, in this study, the complete chloroplast genomes of Jasminum nervosum Lour. and Jasminum multiflorum (Burm.f.) Andrews were sequenced and characterized based on the next-generation sequencing method. Consequently, typical quadripartite chloroplast genomes of 162,855 bp and 163,248 bp were completed for J. multiflorum and J. nervosum, respectively. Comparative genomic analysis among chloroplast genomes of tribe Jasmineae revealed different numbers of repeats, inversion of pafI-pafII region, loss of accD, and loss of clpP introns. Phylogenetic analysis revealed the monophyly of five tribes of Oleaceae. J. nervosum was closely related to J. multiflorum formed compared to other Jasminum taxa. The newly completed chloroplast genomes of Jasminum species enlarged the genomic data and provided useful information for further studies on genomic evolution, population genetics, and phylogeny of Oleaceae.

Understanding the role of soil as a determinant for the selection and establishment of plant species is important, especially in ecotones. Our objective was to explore the composition and structure of various plant communities and their correlation with soil characteristics across the geoenvironmental gradient of Serra da Tenda in Montes Claros, Minas Gerais. To this end, we established three plots (20 × 20 m) across six distinct geoenvironments: Dry Forest in Lowland on Eutrophic Ferralsol, Limestone Pavement with Cambisol, Dry Forest on Limestone with Nitosol, Dry Forest on Drainageway with Nitosol, Cerrado on Side Slope with Cambisol, and Dense Cerrado in Plateau with Ferralsol. We conducted comprehensive chemical and physical analyses of soil samples collected from these sites. We sampled 877 individuals, encompassing 111 species, 76 genera, and 30 families, with the Fabaceae family exhibiting the most significant species richness. The analysis of community composition, relative abundance values, and soil attributes revealed marked differences across the geoenvironments. Canonical Correspondence Analysis (CCA) further demonstrated that soil physicochemical properties significantly influence floristic composition. Our findings underscore the critical role of soil characteristics as fine-scale determinants of plant community composition within the ecotonal landscapes of northern Minas Gerais, highlighting the intricate interplay between soil properties and vegetation patterns in these biologically diverse ecotone zones.

The complete chloroplast (cp) genomes of Delavaya toxocarpa and Harpullia cupanioides were reported here. In D. toxocarpa, the total genome size was 161,325 bp in length, consisting of two IRs (26, 698 bp) separated by the LSC (88,698 bp) and SSC (19,231 bp) regions. The genome contained 131 genes, including 85 protein-coding genes, 37 tRNA genes and 8 rRNA genes, respectively. The GC-content of the complete chloroplast genome was 37.5%. As to H. cupanioides, the complete chloroplast genome was 159, 776 bp in length, consisting of two IRs (26,938 bp) separated by the LSC (87,804 bp) and SSC (18,096 bp) regions. The genome contained 131 genes, including 85 protein-coding genes, 37 tRNA genes and 8 rRNA genes, respectively. The GC-content of the complete chloroplast genome was 37.8%. A phylogenetic analysis indicated that D. toxocarpa was closely related to Koelreuteria, while H. cupanioides was close with Dodonaea viscosa. This study will be useful for the phylogenetic position determination as well as future phylogenetic studies of Delavaya toxocarpa and H. cupanioides.

In almost all species of the genus Passiflora, the plants in the juvenile stage produce leaves with a different morphology when compared to adult plants. During the juvenile stage, Passiflora organensis typically has variegated leaves, and in adult plants leaves are non-variegated and have extrafloral nectaries. Studies have shown that variegation in plants is not just a color change, but has adaptive functions that can benefit plants. We show here that the variegated leaves observed in P. organensis in the juvenile stage occur due to a mechanism in which intercellular spaces are present between the epidermis and palisade parenchyma cells in the adaxial side of the leaves. We also show that both the green and the white-silverish sectors of the leaves contain well-developed chloroplasts, with no significant differences in the efficiency of Photosystem II. We hypothesize that leaf variegation in P. organensis represents an adaptation to protect juvenile plants from herbivores and environmental stresses.

Pollen is a source of information on the reproduction, ecology, evolution, and systematics of plants. Mimosa, one of the largest genera in Leguminosae, has pollen organized in tetrads or polyads, with variation in the arrangement, ornamentation, and size of grains. Despite such morphological diversity, pollen has been described for less than 25% of the more than 600 species in the genus. Here, we increase the current knowledge about Mimosa pollen disparity by extending taxon sampling to 31%. Samples were studied under light and scanning electron microscopy. Novel pollen descriptions and data gathered from the literature were used to infer a pollen morphospace and calculate Mimosa pollen disparity. We find tetrads to be the main dispersion unit, but some taxa also present 8, 12 or 16-grained polyads. Dispersal unities vary in the disposition of pollen grains and size, while grain ornamentation, number of pores and type of aperture were less variable. Analyses revealed an increase in morphological disparity after novel descriptions and an uneven distribution of such variation across major Mimosa clades. Our results expanded the taxonomic breadth of Mimosa pollen diversity, filling gaps and suggesting that although the general picture of pollen morphology in Mimosa is well-defined, the boundaries of its variation remain to be explored.

Anatomical analyses of leaflets from 20 species of legume trees native to Cerrado were conducted using optical microscopy and scanning electron microscopy, seeking to identify anatomical characters that can assist in their taxonomic classification. All the analyzed species exhibited a uniseriate epidermis and collateral vascular system. All of them presented a dorsiventral mesophyll. The epidermis is predominantly papillose, and observed in some species, which is mainly evidenced in Erythrina mulungu, Erythrina falcata, and Senna alata. Except for Bauhinia variegata, Erythrina mulungu, Erythrina falcata, Erythrina verna, Hymenaea courbaril, and Inga laurina, the species showed long cells in the palisade parenchyma. The spongy parenchyma varied in terms of the size of intercellular spaces. Secretory cavities were present in Hymenaea courbaril, and prismatic calcium oxalate crystals were found in the mesophyll of Anadenanthera colubrina and Senegalia tenuifolia. Prismatic crystals were also present in the midrib of Anadenanthera colubrina, Anadenanthera peregrina, Pterocarpus violaceus, and Senegalia tenuifolia. Wax deposition was observed in all species, primarily in the form of plates. Glandular and non-glandular trichomes were identified. Hypostomatic and amphistomatic leaflets were observed, with the paracytic stomata type being the most common. The traits found in the present study corroborate with other studies conducted in Leguminosae reinforcing that anatomical analyses can be useful in the taxonomic characterization of species.

Heteranthery, the presence of different sets of stamens in the same flower, reduces the conflict between effective pollinators and flowers by ensuring adequate resources for the pollinators without affecting reproductive success. Here, we tested the division-of-labour hypothesis in Senna occidentalis, a buzz-pollinated, self-compatible, heterantherous species. The fecundity of pollen grains from long and short stamens was evaluated using hand cross-pollination experiments and by comparing the quantity, size, and quality of pollen in different sets of stamens. The visitation rate and behaviour of floral visitors were also assessed, while their preferences for different sets of stamens were checked using stamen exclusion experiments. The long-pollinating stamens produced a greater number and volume of pollen grains compared to the short-feeding stamens. The pollen grains from long stamens exhibited better germination rates with higher production of fruit and seeds than short stamen pollens in cross-pollination experiments. Nine floral visitors foraged on the flowers, and the large carpenter bees (Xylocopa sp.) were the most dominant and effective pollinators. The long stamens deposited pollen on the lateral and ventral thorax of large-sized pollinators, while the short stamens placed pollen on the ventral and abdomen portions. Therefore, the short stamens might produce pollen grains primarily to feed their pollinators, while the long stamens might generate pollen for pollination and successful fertilization. Further, breeding system experiments indicated a significant pollen limitation and dependency on insect pollination for the increased reproductive outputs (fruit and seed sets). Overall, our findings could indicate a differential distribution of pollen grains in long and short stamens. The differences in the quality and quantity of pollen grains produced by dimorphic stamens of S. occidentalis could fit the division-of-labour hypothesis.

Mimosa caesalpiniifolia Benth. is a bee-pollinated legume tree with significant reproductive success which is widely distributed among Brazilian vegetations. Its reproductive success is attributed to an efficient pollen–stigma interaction. Thus, our objective was to understand the pollen–stigma interaction of this species by describing the morphology of the pollen dispersal unit and the stigma. We aimed to identify characteristics that confirm the “key-lock” interaction process, anticipated in species with clustered pollen dispersion, as found in individuals of the Mimoseae tribe. Anthers and stigmas were sampled from unpollinated and pollinated flowers and processed for surface, anatomical, histochemical and ultrastructural analyses. The embryo sacs and seeds produced were counted in the ovaries and pods, respectively. The pollen is dispersed as acalymmate polyads that are symmetric, with a circular outline in polar view and an elliptical outline in front view; the major diameter mesuares 10.9 µm and the minor diameter, 7.8 µm. Each polyad is formed of eight pollen grains that have an areolate-verrucate exine, along with starch grains and protein bodies as reserve substances. The stigma is semidry, punctiform, with a central hole, cuticularized, composed of cells that secrete proteins, polysaccharides, phenolics, and oil. The discovery of eight pollen grains per polyad, with only one polyad deposited on each stigma, along with the presence of eight ovules per ovary, indicates a key-lock mechanism between the stigma and polyad. This mechanism promotes the fertilization of all eight embryo sacs and results in the production of nearly the same quantity of seeds per pod.