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Plant growth and reproduction patterns may be closely associated with environmental seasonality, but the high diversity of plant strategies has revealed complex phenological patterns. Here, we evaluate the occurrence, duration, and seasonality of vegetative and reproductive phenophases of the Brazilian Chaco vegetation. In addition, we summarize the results of a systematic literature review about the phenology of herbaceous and woody plants in different types of seasonal vegetation in the South American Dry Diagonal. Woody plants have a high intense leaf fall and low leaf flush during the dry season in the Brazilian Chaco, whereas in herbaceous plants these phenophases have more fluctuations. In both types, flowering and fruiting are continuous, not uniform, and mainly concentrate during the rainy season. However, woody species present two intensity peaks independent of rainfall, mean temperature, photoperiod, or soil water availability. In turn, in herbaceous species, flowering and fruiting responded to local climatic variables and photoperiod, presenting a peak of intensity during the rainy season. The rainy season plays an important role in plant growth and reproduction in seasonal climates around the world, mainly due to the energetic demand for plants. Like other vegetation types with seasonal climates, particularly in the South American Dry Diagonal, the Brazilian Chaco presents a wide range of phenological patterns, with generally different patterns between woody and herbaceous species. Community-level phenological studies conducted in areas with a seasonal climate have globally focused only on reproduction in relation to vegetative phenology, mostly ignoring herbaceous flora. Here, we emphasize that the phenological complementarity between the woody and herbaceous components is of great importance in maintaining the availability of resources.

Light, despite being essential for photosynthesis, can become an environmental stressor, since at high incidence it can induce photoinhibition. In tropical regions it is known that invasive C4 grasses maintain higher photosynthetic performance than C3 grasses. That is why we evaluated the dynamics of photosynthetic parameters in different grass species of the Brazilian Savanna (Cerrado), taking into account whether they are native or invasive, and have C3 or C4 photosynthetic metabolism pathway. The native species evaluated were Echinolaena inflexa, Trichanthecium cyanescens (C3) and Loudetiopsis chrysothrix (C4), and the invasive species Melinis minutiflora and Urochloa decumbens (C4). We evaluated chloroplastic pigment content, chlorophyll a fluorescence, leaf gas exchange and photochemical energy partitioning on fully expanded and undamaged mature leaves. Results indicate that leaf gas exchange varied throughout the day for all grass species. The invasive species showed higher CO₂ assimilation rates and water use efficiency and lower values of stomatal conductance than native species; however, all species showed a decrease in potential photosynthetic quantum yield at midday. Regarding chloroplastic pigments, chlorophyll a was the only one that presented a difference between the C3 and C4 plant species, and there was no difference between species in the photochemical energy partitioning. Although they occur at the same place, the species showed different responses even when comparing the same type of photosynthetic metabolism. The C4 native species L. chrysothrix was the one that showed values closer to those obtained for the invasive C4 species and may be an alternative in management strategies.

The challenges arising from environmental stress conditions and the intrinsic limitations of their sessile nature strongly affect plants throughout their life cycle. Evolutionarily, plants have developed mitigation strategies, such as acclimation and phenotypic plasticity, to thrive in diverse environmental conditions. In semi-arid environments, light stress plays an important role in seed germination. The objective of this study was to experimentally assess the variability in the phenotypic expression of germination among genetic families of the cactus Mammillaria carnea obtained from different micro-environments along a light stress gradient. Specifically, we investigated germination under white light and far-red-rich light conditions, aiming to simulate lighting conditions with and without canopy cover. The highest germination percentages were observed under white light conditions. However, within the micro-environments associated with Neltuma laevigata and Parkinsonia praecox, greater phenotypic variability and genetic independence were evident under far-red-rich light compared to direct solar radiation. This suggests that while high light intensity enhances seed germination, it also reduces phenotypic expression variability, potentially resulting in decreased evolutionary adaptability in M. carnea populations in high-light stress environments.

Climate change could significantly affect the geographic distribution of plant species. Hedeoma multiflora is a vulnerable medicinal and aromatic herb that distributes in the Pampa, Espinal and Chaco biogeographic provinces in austral South America. This integrated approach combines ecological models and cytogenetic evidence to assess the effects of climate change on this species. Species distribution modelling using the Maxent model was implemented under current climatic conditions and three future climate change scenarios, integrating data from three Global Climate Models. The most suitable areas span 68,557 km², encompassing the Sierras Pampeanas in San Luis and Córdoba provinces, and the Tandilia and Ventania systems in Buenos Aires, Argentina. The primary variables influencing the models include elevation (500 to 2000 m.a.s.l.), annual mean temperature (10 to 17 °C), annual precipitation (500 to 900 mm) and precipitation seasonality (50 to 75%). While the results project an expansion in the potential distribution of the species, heterogeneous patterns of range shifts are predicted across the three mountain systems: expansion in Sierras Pampeanas, march in Ventania and retraction in the Tandilia system. Variations in chromosome numbers within four distinct localities were reported, indicating the presence of polyploidy. This could potentially provide adaptive advantages in response to changing climates. This plant lives in habitats that face human-induced alterations and insufficient area protected coverage, then we propose strategies for both in situ and ex situ conservation of this medicinal species in each area.

The scaling relationships between leaf dry mass (LDM) and surface area (LA) can reflect the efficiency of light harvesting and photosynthesis, as well as the ability of plants to withstand biotic and abiotic stress. However, it remains little unknown whether plants alter the scaling relationships of LDM and LA, as along with leaf mass investment per unit area in common species growing in different habitats with high temperature and contrasting water availability. This study involved measuring LA, LDM, and leaf morphological traits (e.g., leaf thickness, dry mass per unit area, and density) in 14 woody species (10 tree species, 2 shrub species, and 2 liana species) that co-occur in wet-hot (WH) and dry-hot (DH) habitats in southwest China. Our results showed that the scaling exponents (α) of LDM vs. LA were consistently greater than 1.0 (indicating the increase in LA fails to keep pace with increasing LDM) for all 14 common species at both sites, irrespective of their growth forms. Furthermore, species exhibited a higher leaf mass investment per unit area and leaf density at the DH site compared to the WH site. These results suggest that the law of “diminishing returns” applies to the scaling relationships of LDM and LA in common species inhabiting both types of habitats. Additionally, plants at the DH site increased leaf mass and density investments, potentially reflecting an essential adaptation to strong selective pressure experienced by plant species in that habitat. This study provides new insights into the scaling relationships of LDM and LA in contrasting habitats, enriching our understanding of the plant life-history strategies and adaptations in response to climate change.

Climate change impact on species can be heterogeneous depending on their environments, exposure, and intrinsic characteristics. Likewise, global warming may have an uneven effect on lineages, depending on whether phylogenetic conservatism or divergence of ecological niches predominates during clade diversification, imposing a higher risk to species groups from certain regions, habitats and lineages. This study evaluates the impact of future climate change on Menonvillea, a genus with 24 species distributed along the Andes and contiguous regions of the Southern Cone. The impact on the main phylogenetic, ecological and biogeographic groups is evaluated, also analyzing the effect on its richness and phylogenetic diversity. Results show a strongly negative impact on most species of the genus. However, the greatest pressure seems to be recovered for high Andean species, mainly from the southern portion of the Southern Andes (between 34°S–53S°), and mostly included in Menonvillea sect. Cuneata. Richness appears to be more impacted in high Andean regions, and the loss of phylogenetic diversity is greater than expected at random. These results highlight the strong negative impact that climate change can induce on lineages distributed in the Andean-Patagonian region, and that show patterns of phylogenetic niche conservatism.

Pollination biology is anchored in natural history studies, defined broadly as the practice of observing and describing an organism's behaviour, interactions, and association with the environment in detail. Remarkable or unexpected observations of natural phenomena involving organisms are then interpreted in the light of prior knowledge. Valuing a variety of approaches to natural history studies from around the world, this Special Issue (SI) in FLORA brings together 29 articles to celebrate the career of Professor Marlies Sazima, who pioneered and influenced a generation of pollination biologists in Brazil. This collection puts together a mix of different studies, from detailed descriptions of the function of floral traits, pollinator foraging behaviour, and their effects on plant fecundity, to studies that scale up natural history information to untangle complex ecological patterns at the level of populations, communities or entire ecosystems. The SI also includes studies that make use of people's fascination with documenting natural phenomena, by using citizen science data as well as compiling data from the literature to produce comprehensive global reviews. We included studies with broad scopes and approaches on purpose, taking liberty with the definition of natural history, to highlight the fundamental practice of observing actual interactions between plants and pollinators in pollination biology studies, as well as to celebrate the diverse contribution made by Prof. Marlies throughout her career. We hope to continue mirroring her fascination with natural history and foster the next generation of scientists to carry on her legacy.

Cucurbita pepo L. is popularly known as pumpkin or zucchini. Compared to the others of the genus, it presents the greatest genetic variability. Thus, given its nutritional and medicinal benefits, it results in many widely cultivated and economically important specimens. Due to this, differentiation between specimens becomes necessary, mainly pumpkin and zucchini which have different characteristics, however they receive the same scientific nomenclature (C. pepo). It is noteworthy that the anatomical knowledge of the specimens helps with taxonomy. Furthermore, due to the economic value, when it comes to vegetative propagation, the identification of structural aspects is important for the success of propagation, which depends on the regeneration of plant tissues. This study aimed to characterize and differentiate two specimens of C. pepo through morphoanatomy and histochemistry. For anatomical study, usual methods in plant anatomy were used to prepare and analyze, under an optical microscope, semi-permanent slides containing transverse sections of the roots, stems, leaves, and paradermic sections of the leaf blades of C. pepo specimens. Histochemical tests were performed on cross-sections of the specimens' leaf blades to locate chemical compounds. The optical microscopic evaluation enabled the anatomical characterization, revealing distinct characters among the specimens. For example, the zucchini shows crystals in the root. Meanwhile, the pumpkin shows sclerenchymatic pericycle in the stem and secretory ducts in the stem and leaves. Histochemical techniques showed the presence of different compounds, differentiating in the presence of starch in the zucchini and triterpenes and steroids in the pumpkin. Correct characterization provides important information for quality control of the plant drug and taxonomic differentiation of the specimens since diagnostic characters vary.

The subfamily Dialioideae comprises 17 genera and 83 species, having a pantropical distribution. Dialium L., the typical and most diverse genus of the subfamily, contains 34 accepted species, of which five are Neotropical. The other genera of Dialioideae are restricted to specific continents. Noteworthy, five genera are exclusively Neotropical, namely Androcalymma Dwyer, Apuleia Mart., Dicorynia Benth., Martiodendron Gleason, and Poeppigia C.Presl. This article presents a palynological study of 21 taxa belonging to six genera of the subfamily Dialioideae, including the above-mentioned five Neotropical genera and the Neotropical species of Dialium. The aim was to characterize pollen grains and thus provide support for the taxonomic circumscription of the group. Pollen grains were acetolysed, measured, described, and illustrated using light microscopy. Surface details and apertures were examined on unacetolysed pollen grains by scanning electron microscopy. The parameters evaluated were shape, size, aperture type, polarity, and exine ornamentation. The analyzed species have medium-sized pollen grains. Pollen shape ranges from isopolar to subprolate, prolate, oblate-spheroidal, prolate-spheroidal, and perprolate. The polar area is small or large, tricolporate, syncolporate, or parasyncolporate in some species, with short, wide, or narrow colpi, ornamented or slightly ornamented membrane, lalongate or lolongate endoaperture, and rugulate, microreticulate, or striate sexine. The sexine is as thick as, thicker than, or less thick than the nexine. Pollen attributes were successfully used to construct a key to distinguish genera and species. The findings show the importance of pollen morphology in the taxonomy of Dialioideae, allowing identification of taxa.

As species are fundamental units of evolutionary biology research, accurate species delimitation plays a crucial role in current biodiversity management. The Qinghai-Tibet Plateau (QTP) comprises one of the global biodiversity hotspots, and plant speciation and its evolutionary history in this region still need much research. Aconitum pendulum and A. flavum (Ranuculaceae) are mainly distributed in the QTP and its adjacent regions. The two species have extremely similar morphological characteristics, and their evolutionary relationship is still controversial. In this study, we collected 244 individuals in 14 populations from the main distribution areas of the two species. Genome-wide single-nucleotide polymorphisms (SNPs) from genotyping-by-sequencing (GBS) of A. pendulum and A. flavum were obtained to decipher the taxonomic delimitation and explore the evolutionary history. We performed neighbor-joining (NJ), PCA, structure, and niche overlap analyses. None of them support that A. pendulum and A. flavum can be considered as two separate species. In addition, the genetic difference between species is less than that among populations. We propose merging the two species into one. We also found that the genetic difference between the two species was not associated with morphological species or geographic distance. Gene flow and genetic drift may play a crucial role in weakening the correlation between genetic distance and geographical distance. A bottleneck effect occurred in the two species during the last glacial maximum. Based on the Maxent and Stairway Plot results, we inferred that A. pendulum and A. flavum still had large survival ranges during the LGM, similar to other cold-tolerant species. Furthermore, human activity, such as overexploitation causing habitat fragmentation, might be one of the factors that threat to the survival of A. pendulum and A. flavum in the current period.