Flora最新文献

This work is part of a bigger project to study the spore morphology of isosporous ferns growing in the Calilegua National Park (CNP), in the province of Jujuy, Argentina. This park belongs to the phytogeographic region of the Yungas, where climatic and terrain conditions are optimal for the growth of ferns. The aim of this work is to present the morphology of the spores of 53 taxa corresponding to 6 families of isosporate ferns that grow in this protected area. The study was carried out with herbarium material and field trips. The families studied are Hymenophyllaceae, Ophioglossaceae, Polypodiaceae, Pteridaceae, Thelypteridaceae and Woodsiaceae. According to the spore aperture type, 24 taxa are monolete and 29 trilete. The spores are yellowish, light to dark brown or brown greenish. The largest spores belong to Pleopeltis tweediana and the smallest to Polyphlebium angustatum. The ornamentation observed were echinae, folds, wings, reticles, cristae, verrucae or rugulae. The spores of 35 species are illustrated for the first time under the light microscope and five species with scanning electron microscope. An identification key of the spores is also provided. The morphological characteristics of the spores allowed the identification of 16 species, contributes to spore bank analysis, aero and palaeopalynological studies and taxonomic identifications.

The genus Psittacanthus is distributed from Mexico to Argentina and contains c. 110 species. The large, lipid-rich, one-seeded fruits of Psittacanthus species frequently depend on frugivorous birds for seed dispersal; however, fruit morphology of Psittacanthus (Loranthaceae) mistletoes remain poorly studied. In this study we describe the fruit morphology of nine Psittacanthus species. Fruits were collected from the study sites in which mistletoe plants were inhabiting contrasting habitats and host tree species. The morphological characteristics of fruits by species were described and compared with the use of inclusion and staining techniques and light microscopy. Our results show that fruit size varies among species, with P. macrantherus having the largest fruits. Most fruits have an ellipsoid to ovoid shape, color of fruits transits from green when immature to red or purple before ripening to blackish or purplish black, with color variations observed in different species, and the cupular pedicel length varying among species. Fruit sections indicate the following parts: exocarp, viscin layer, seed coat and a dicotylar to polycotylar embryo, with P. schiedeanus having the highest cotyledon count. No endosperm is present in the studied species. Our results provide valuable information for further species comparisons regarding the lack of endosperm and polycotylar embryo. Additionally, interspecific variation in cotyledon number and seed coat highlights distinct processes, including the potential effects of environmental differences.

Extreme drought events, driven by the El Niño Southern Oscillation (ENSO), are linked to increased tree mortality and alterations in vegetation structure, dynamics, and floristic composition in tropical forests. Existing analyses, primarily focusing on Africa, Central America, and Amazonia, overlook the floristic impacts on biome transitions. This study evaluates the profound effects of the severe 2015/2016 ENSO event on tree density and floristic composition in the critical transition zone between Amazonia and Cerrado, South America's largest biomes. Our findings not only document significant biodiversity loss but also offer insights into species resilience, guiding conservation strategies under changing climate conditions. We inventoried long-term plots before and after the extreme drought event, sampling 12,465 individuals from 526 species, 224 genera, and 65 families, in Open Ombrophilous Forest (OF), Seasonal Forest (SF), Cerradão (CD), and Typical Cerrado (TC). We document the disappearance from our plots of 97 species after the ENSO, with only 61 new species being recorded. The total loss of individuals across the transition zone was almost 10 %. The SF and CD forest plots showed the greatest replacements, species losses, and reductions in tree density. Their markedly seasonal baseline climate probably drove these changes. In most phytophysiognomies, there was an increase in pioneer species and drier environment habitat specialist species, indicating that although many species are vulnerable to extreme climate events, others benefit, especially those with a short life cycle. We found that the vegetation of the Amazonia-Cerrado transition overall is vulnerable to climate anomalies, with widespread loss of tree density and change in floristic composition. Our study also provides a species-by-species list of the most vulnerable and resistant trees which helps point to overall climate change vulnerabilities and assist with initiatives to recover degraded areas.

Gynodioecy is a sexual system in which hermaphrodites coexist with females and is frequently observed in Lamiaceae. The aim of this study was to investigate the floral morphology of Elsholtzia angustifolia (Loes.) Kitag (Lamiaceae) using stereomicroscopy (SM), light microscopy (LM), and scanning electron microscopy (SEM) to identify floral dimorphism in a potential gynodioecious species. Two different floral morphs were found in Elsholtzia angustifolia, hermaphroditic and female individuals, from three natural populations in South Korea (Ihwa Pass, Mt. Joryeong, and Mt. Sokli). However, females rarely occur in natural populations. Statistical analysis revealed significant size differences in the floral organs of the floral morphs. Micromorphological and anatomical characteristics were also examined using LM and SEM to compare the differences between the female and hermaphroditic types, revealing significant differences in the stamens between the two sexual types. Additionally, floral scent analysis was performed to identify floral morph-specific scent components, with elsholtzia ketone and dehydroelsholtzia ketone as the major components.

The evolution of pollination systems is unclear for many plant taxa due to the scarcity of field observations on floral visitors. Supposed bat- and bee-pollination is reported for species of the genus Cayaponia, but <5 % of these were observed in the field and their pollinators recorded. We studied the pollination biology of two early diverging sister species of Cayaponia, C. cabocla and C. pilosa, recording the floral biology, phenology, breeding system, floral visitors, and floral scent chemistry. Both species are monoecious and have bell-shaped white to greenish flowers. The length of the C. cabocla flowers was 2.33 ± 0.52 cm and of the C. pilosa flowers it was 2.75±0.95 cm. In C. cabocla nectar volume of male flowers was 180±57.15 μl and sugar concentration was 28.75±0.95%, whereas in female flowers the average volume was 46.5 ± 10.24 μl and sugar concentration was 22.5 ± 0.57%. Cayaponia cabocla flowers opened at late night, around 03:30 h, whereas those of C. pilosa opened around noon. Both species bloom in the austral summer (January-February) and depend on bees to set fruit, in addition to having a few floral visitor species in common. Whereas some of the flower traits resemble those of bat-pollinated plants (most notably the large nectar volume and nocturnal anthesis), the floral volatiles of both C. cabocla and C. pilosa are typical of flowers pollinated by bees. This study clarifies the pollination system of two Cayaponia species and provides new information that can be used to reconstruct pollination system transitions in this rich genus of cucurbits.

The ninth largest family of angiosperms is Myrtaceae, which comprises 127 genera and over 6000 species. The leaf anatomy of Myrtaceae has been widely studied and can be used in phylogenetic analyses and species delimitations in complexes within the family. A multiple epidermis and hypodermis have been described for the leaves of representatives of the family but have not been confirmed using ontogenetic studies, which could lead to incorrect interpretations about these tissues. Thus, we studied the leaf ontogenesis of the following 9 species in subfamily Myrtoideae: tribe Syzigieae - Syzigium cumini; tribe Myrteae - Myrceugenia alpigena and M. euosma (subtribe Luminae), Psidium sartorianum, P. guajava, Campomanesia adamantium and Pimenta pseudocaryophyllus (subtribe Pimentinae), Myrcianthes pungens and M. gigantea (subtribe Eugeniinae). Shoot apices and leaves up to the fourth node were transversally and longitudinally sectioned following techniques used for plant anatomy. Leaf development in all species is from apical, intercalary, dorsal, marginal and plate meristematic activity. Protodermal periclinal divisions only occur to give rise to secretory cavities. The results show that in all the species the subepidermal layer is a hypodermis, which originates from periclinal divisions of the ground meristem. The occurrence of this layer could have phylogenetic implications according to reports in the literature, reinforcing the relationships among the subtribes in current topologies of Myrteae. However, the occurrence of a hypodermis in representatives of other subtribes of Myrteae and Syzigieae need to be better studied and discussed in relation to the phylogeny of Myrtaceae.

Acid rain is one of the major contributors to the loss of tropical forest. Although the effects of acid rain in leaf anatomy have been widely studied, its impact on specialized secretory structures remains unknown. The aim of this study was to investigate the morphoanatomical changes in the extrafloral nectaries of Cedrela fissilis in response to simulated acid rain. Each seedling was sprayed with 50 ml of an acidic solution daily for 19 consecutive days. Anatomical and micromorphological changes in the nectaries were described. The treated plants exhibited plasmolysis and disruption of epidermal cells, cell collapse, hypertrophy, plasmolysis, phenolic and starch accumulation in the nectar-secreting cells, and the formation of a wound healing tissue. The results indicate that the nectaries of C. fissilis undergo alterations when exposed to acid rain, which may compromise the functioning of the entire structure and potentially impact plant-insect ecological interactions.

Parasitic plants are known for shaping plant communities, mainly by suppressing dominant species. This suppression, in some cases, fosters species coexistence and boosts overall diversity. Recent studies reveal that certain parasitic plants can curb invasive alien plants or expansive native species. In this study, we followed previous case studies, investigating the ability of three common Central European hemiparasitic species to attach to roots and form functional haustoria across a broad range of invasive and expansive hosts. For each host-hemiparasite pair, we posed two questions: (i) Do the hemiparasites produce haustoria on the host's roots or rhizomes? (ii) Does the anatomical structure of the haustoria include all features necessary for their functionality? We cultivated three hemiparasitic species, Melampyrum arvense L., Rhinanthus alectorolophus (Scop.) Pollich, and Odontites vernus subsp. serotinus (Dumort.) Corb., in pots with 18 candidate hosts. After cultivation, we dissected the root systems to determine haustoria abundance and to collect them for anatomical study to assess their functionality. Hemiparasite individuals in each pot were also counted. The hemiparasitic species produced haustoria on the majority of tested hosts (37 out of 44 combinations), with little difference between native expansive and alien invasive plant species. In 13 host-hemiparasite combinations (including eight combinations with invasive species), we identified abundant functional haustoria and good establishment of the hemiparasites. Remarkably, all three hemiparasitic species formed functional haustoria on invasive Asteraceae hosts. By contrast, Melampyrum arvense performed poorly when cultivated with grasses. We identified a series of hemiparasite-host combinations, which should be further tested for the potential hemiparasite effect on host fitness in the field. The abundance and anatomical structure of the haustoria indicates that the recognised low specificity of the hemiparasitic interactions applies also to associations with alien invasive species, with which they do not share a common evolutionary history.

Ultraviolet (UV) radiation is known to be an important environmental stressor of plants. Evidence of its effects on plant reproduction is mixed, with studies usually showing that short doses of UV lead to a reduction in pollen viability, but that longer exposure can improve viability. Here, we tested the effect of UV intensity (control, low-UV, high-UV) and the duration in which the plants were exposed for different time periods prior to flowering (long: from seed; short: exposed after 7 days of growth) on pollen viability of Brassica rapa. We also tested how changes in floral morphology (UV-absorbing area) related to pollen viability, before carrying out a meta-analysis on the effects of UV on pollen performance. We found that high UV intensity reduced pollen viability, but there was no effect of UV exposure prior to anthesis on pollen viability. Unexpectedly, we found a negative relationship between UV-absorbing area and pollen viability. Our meta-analysis showed a significant negative effect of UV on pollen viability, tube growth and germination. In summary, our results show that high UV generally negatively impacts pollen viability.

Urbanization is among the main drivers of global biodiversity changes. Urban areas are increasing faster, particularly in global biodiversity hotspots. Therefore, more evidence is needed on how urban gradients drive plant traits and interactions with herbivores in neotropical regions. Here, we investigated how urbanization intensity and habitat permeability affect metrics (species richness, composition and vegetation cover), functional traits, and herbivory of plant communities, focusing on spontaneous native and non-native species in a neotropical city in Brazil. Non-native species represented 64.6 % of the occurrences, and habitat permeability had a stronger influence on plant communities than urbanization intensity. The intensity of urbanization decreased the species richness and increased the specific leaf area in native and non-natives plants. Habitat permeability also affected species composition. Permeable habitats had higher vegetation cover, herbivory, and height of the non-native communities. Life forms as geophyte for non-natives, chamaephyte, and hemicryptophyte for natives, and zoochoric dispersal syndrome were more frequent in permeable habitats. Impermeable habitats had higher frequencies of therophyte life form, and autochoric dispersal syndrome for native species. The higher vegetation cover, the lower direct interference from humans, and the permeability of habitats allowed more different functional traits within plant community and more interactions between plants and herbivores along the urbanization intensity gradient. The permeability of urban habitats, in a medium-sized neotropical city, has greater influence on the variation of the plant community than the intensity of urbanization. This highlights the importance of the presence of permeable areas in supporting plant biodiversity within highly paved urban gradients.