Flora最新文献

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.

Peliosanthes meghalayensis, a new species from Wari Chora gorge in Meghalaya, NE India, is described and illustrated. It is similar to P. pumila from Khasia, NE India, in its small habit and having flowers fewer than 10, but differs chiefly by the knobby rhizome, broader leaf blades with closer transversal veinlets, slightly larger cernuous flowers, and pistils with 6 distinct ridges. On the other hand, in Assam, NE India, we rediscovered P. subspicata, which had been known only by old collections made in NE India and Bangladesh in the 19th century. We supplementarily describe and illustrate it based on living collections. We treated P. bipiniana as conspecific with P. subspicata.

Capsule-type fruits are predominant in Bromeliaceae. However, the late divergent subfamily Bromelioideae generally presents fleshy fruits, which display a diverse range of morphologies even in related genera; however, there is almost no information regarding their anatomical and ontogenetic aspects. In this study we evaluate the fruit ontogeny of species from the major lineages of Bromelioideae, to better understand the possible paths in which fleshiness can be achieved in the subfamily. Flowers at pre-anthesis and anthesis, and fruits of Acanthostachys strobilacea, Billbergia pyramidalis, and Bromelia antiacantha were collected and processed with standard methods for analysis under light microscopy. Two basic ontogenetic pathways for achieving fleshiness were identified among the examined species. In the two former species, belonging to the core Bromelioideae, the pericarp development occurs solely through cell expansion and anticlinal cell division in the mesocarp. Conversely, in B. antiacantha, belonging to the tankless lineages, the pericarp development proceeds via both periclinal and anticlinal cell divisions of the outer and inner mesocarp. The analysis of fruit anatomy in the species included in this study highlights unprecedented traits of Bromelioideae fruits, such as the presence of the pericarp´s massive extra-carpellary portion in B. antiacantha, which contains many mucilage channels and fibrous tissue, and an intrusive septum in the carpellary portion, which acts as the main nutritive portion of the fruit. Additionally, in the present study, unique features of the ovary and the fruit, essential for characterizing the species were detailed, including the elongated placental tissue and the aliform projections of A. strobilacea. Our observations highlight distinct developmental processes to fleshy fruit formation in Bromelioideae. In this way, exploring the fruit ontogenetic diversity in Bromelioideae offers an exciting opportunity for future investigations. Besides, the unique fruit features identified bring out the importance of fruits as tools for genus delineation within this subfamily.

Tropical forests play an important role in maintaining, replenishing and conserving a large portion of the planet's biodiversity. However, these forests have been converted into anthropic landscapes, threatening the persistence of wildlife. The exploitation of forest products can result in different ecological impacts at different levels of biological organization. In this study, we propose a vulnerability index to examine the susceptibility of woody plants used by locals in a human-modified landscape of the Caatinga dry forest (i.e., the Catimbau National Park). We contrasted patterns of (1) plant use by local people (risk of use, collection risk, local importance, and diversity of use), (2) plant reproductive strategies (pollination, sexual and reproductive systems, dispersal mode, flowering and fruiting phenology), and (3) the conservation status of the plant species. We combined this information to propose a vulnerability index expressing species sensitivity to human disturbances in 14 regenerating and 14 old-growth forest stands. We tested the hypothesis that regenerating forest stands will harbor more vulnerable plant species compared to old-growth forest stands. Among the 119 plant species registered in regenerating and old-growth forest stands, 80 species (67.2 %) were recorded as useful for local people in Caatinga. Specifically, about 71.8 % and 70.5 % are exploited by the rural population for some type of use in regenerating and old-growth forest stands, respectively. The most frequent type of use was medicinal, followed by construction and fuel in both regenerating and old-growth forest stands. Regarding the potentially collected plant parts, the total removal of the individual and collection of leaves exhibited similar and higher relevance in regenerating, while leaves were the most collected part in old-growth forest stands. Of the 80 plant species analyzed, 62 % and 58.5 %, respectively, were classified as exhibiting moderate and high vulnerability to extirpation in regenerating and old-growth forest stands; thus not supporting our hypothesis. Our results suggest that in the Caatinga dry forest, (1) woody plant species responsible for forest regeneration in the context of slash-and-burn agriculture are exploited for multiple uses, (2) medicinal use is the main type of use of woody plants occurring in regenerating and old-growth forest stands, (3) total removal of the individual and collection of leaves were the most collected plant parts, and (4) both regenerating and old-growth forest stands showed a high vulnerability to human disturbances in the study area. In the long term, the exploitation of vulnerable plant species may negatively affect the composition and structure of the community and, consequently, the rate and trajectory of succession. It can be expected that as populations of vulnerable plant species are reduced or extirpated from the community, ecological interactions such as pollination and dispersal, which ar