Brazilian Journal of Botany

Ecological approaches, such as functional groups (sensu Reynolds, FG) and exclusively morphological-based groups (sensu Kruk, MBFG), have provided a reliable tool for understanding phytoplankton responses to environmental conditions. Our study evaluated the concordance and the response of these two-functional classifications of the phytoplankton community to environmental variables in reservoirs of different trophic states (ultra-oligotrophic to meso-eutrophic). We also investigated the spatial and temporal concordance of the functional classifications with the taxonomic-based classification (species). Integrated water samples were collected in the euphotic zone in two climatic periods (summer and winter) to determine physical and chemical variables and phytoplankton. Higher water temperature and thermal stratification were observed in the summer, whereas higher free CO2 concentrations and mixing regime of water column in the winter. The 35 descriptors species showed a greater relationship to the trophic conditions of the reservoirs. The functional classifications revealed that the 17 FGs and 7 MBFGs were influenced primarily by seasonal variation of limnological conditions (water temperature, CO2 concentration, Zmix depth) and secondarily by trophic state of the reservoirs. Stronger similarity (higher than 0.70) was verified between species and FGs matrices (Mantel test, mainly) than between species and MBFGs ones. Procrustes and Mantel tests also evidenced high concordance between FGs and MBFGs matrices, exhibiting similar spatial and temporal distribution to environmental conditions. Thus, these ecological classifications demonstrated to be complementary tools, besides their particular degrees of detailing, to elucidate the functional responses of numerous phytoplankton species in studied tropical reservoirs.

Arid and semi-arid ecosystems are widely distributed around the world, covering about 60% of the earth’s land area. This type of ecosystem has low resilience and high fragmentation caused by human activities related to land use changes to agricultural uses. It has been seen that one of the mechanisms that can help recover the structure and functioning of this type of ecosystem is facilitative interaction. It has been documented that in these environments, the greatest recruitment and establishment of seedlings occur under the cover of a nurse plant. This has led us to investigate whether the life forms of the benefited plants have any relationship with this type of interaction, since the presence and distribution of beneficiaries of particular life forms may result from the evolution of the facilitating interaction. In total, we registered 16 nurse species in the sampling sites, and underneath the canopies of these species, we recorded approximately 250 individuals benefiting from these plants. The majority (51%) were succulent plants, followed by shrubs comprising 27.5%. The functional attributes of the nurse plants that were most strongly associated with the succulent life form were height (H) and canopy density (CD) (Axis 1 of the PCA), as well as leaf area (LA) and specific leaf area (SLA) (Axis 2). These relationships may be due to the fact that succulents seek out nurse plants that have ample canopy cover for the best protection. These findings may help in the selection of effective nurse species for restoring functional diversity in degraded drylands.

In natural environment, plants consist of both metabolic and tolerant mechanisms in toxic non-essential metals like Arsenic, Cadmium, Lead and Mercury. Natural activities composed of mining and smelting operations, including some haphazard practices in agriculture, have extensively contaminated some areas around the world—as for instances, in India, Japan, Indonesia and China by Cadmium, Copper and Arsenic and Copper and Lead in Greece. In fact, South-East Asia is suffering from the contamination of the groundwater Arsenic, as in the same way the existence of Copper, Lead, Nickel, Zinc and Cadmium is nothing new in some parts of Australia. Indeed, heavy metal contamination has become a worldwide problem. The uptake as well as accumulation of the aforesaid metals by plants is the main factor responsible for threatening the health of both man and animal into their food by toxic metals. The production of phytochelatins, a metal-binding thiol peptide and metallothionin, to react against the heavy metal stress may have provided for an appropriate metal tolerance in plants but needs a comprehensive study on it; for a better understanding on the different metal transports, their accumulations as well as over expressions in plants would definitely pave the better ways to develop metal tolerant plants or transgenics. Keeping the rising concerns over heavy metal stress affecting agriculture produce and plants in view in water; this review aims at throwing light as a tip on the iceberg about the physiological and biochemical mechanisms of metal accumulations, their responses and detoxification to the toxicity as well as to the metal stress tolerant plants.

Abiotic and biotic factors constrain species occurrences, although many species are widely distributed. We investigated the performance of two populations of Hirtella glandulosa Spreng. (Chrysobalanaceae), a tropical tree or shrub that occurs from Venezuela to southeastern Brazil. This study was carried out in two evergreen Atlantic Forests fragments in the Chapada Diamantina Mountains (Brazil) growing on sites with different soil types and different water availabilities: a river margin on litholic soils (river/lithosol) and a plateau with the deep clayey soils (plateau/latosol). We examined leaf phenology, water potential (ΨW), wood density, leaf traits, and leaf gas exchange of populations growing at both sites in the rainy and dry seasons. Despite differences in their ΨW values, both populations maintained similar leaf phenological patterns. Leaf traits, ΨW, and leaf gas exchange differed spatially and temporally. The maintenance of phenological strategies conditioned by distinct leaf and gas exchange traits compensated for lower water potential levels in the river margin/lithosol site and favored the maintenance of a positive water balance and greater water use efficiency than in the plateau/latosol site. Morphological and physiological trait adjustments could allow the wide distribution of H. glandulosa in contrasting soil types with different water availabilities.

Gynostemma guangxiense X.X.Chen & D.H.Qin is an important medicinal species distributed in Guangxi, China. In this study, we obtained the complete chloroplast (cp) genome sequence for G. guangxiense using Illumina paired-end sequencing technology and analyzed the codon usage pattern with bioinformatics approaches. The cp genome of G. guangxiense comprises 157,785 bp with a pair of inverted repeat regions (26,288 bp) separated by one large single copy region (86,702 bp) and one small single copy region (18,507 bp). The whole genome contains 130 unique genes, where 113 are unique, including 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. In addition, 62 repeats and 70 simple sequence repeats were identified. Phylogenetic inference based on 73 protein-coding genes indicated that G. guangxiense has a close relationship with Gynostemma caulopterum S.Z. He. In addition, 52 CDSs longer than 300 bp in the G. guangxiense cp genome were screened to analyze synonymous codon usage. The neutrality plot indicated a weak correlation between GC12 and GC3. Effective number of codons plot analysis showed that most genes were distributed below the expected curve. PR2-plot mapping analysis revealed that G and T were used more frequently than C and A at the third base position. Finally, 16 codons were identified as the optimal codons. These findings suggest that natural selection has mainly influenced codon usage in the G. guangxiense cp genome. The results obtained in this study of G. guangxiense provide an important theoretical basis for its molecular identification, utilization, and conservation.

This study evaluated soil properties and their relation to root production and arbuscular mycorrhizal fungi (AMF) colonization of grasses. Soil samples were collected from surface layers to determine the volume, total length, specific length, diameter and dry mass of roots, and grain size and chemical properties of the soil. Sampled roots were used to evaluate mycorrhizal colonization and 50 g of soil to extract spores. A second sampling was conducted to measure soil penetration resistance, macroporosity, microporosity, total porosity and bulk density. Of the morphological traits of the roots, only specific length and diameter were significantly related to soil physical attributes. Root volume was positively related with P, Ca, Mg and organic matter. Almost all of the mycorrhizal variables had no correlation with the physical properties of the soil; only total colonization was positively related to soil penetration resistance (to 0.10 m). AMF had a negative correlation between root colonization and total length of the roots, while the number of spores was inversely related to roots finer than 0.5 mm in diameter and positively related to roots larger than 0.5 mm in diameter. The data were highly variable, indicating the influence of environmental heterogeneity on the investigated characteristics.

Phenological studies are fundamental for understanding the structure and dynamics of the plant community and assist in understanding the influence of climate on vegetation and for the analysis of plant-animal interactions. In this work, we present the phenology of 19 woody species of coastal dunes located in the eastern end of the Amazon coast. We evaluate the phenological aspects of the community and their relationship with climatic factors (photoperiod, precipitation, and temperature). For this evaluation, 19 woody species with a diameter at soil height (DBH) > 3 cm and whole crown visible were selected. Information on leaf abscission, new leaves, flowering, and fruiting was collected fortnightly. The activity and intensity of each phenophase were estimated according to the Fournier index. Circular statistic was employed to determine the mean dates for the start and peak of the phenophases, and the percentage of activity and intensity for each phenophase. Multiple linear regression analysis was applied to investigate the relationships between phenophases and climatic variables. Additionally, leaf habits and pollination and dispersion syndromes were defined for each species. The results reveal that the species evaluated did not show seasonally defined behavior, nor were they related to the climatic factors evaluated. Most species showed evergreen leaf habit (83.4%), melittophilly as the primary pollination syndrome (78.9%), and zoochoric dispersal (84.22%). Although it does not present a seasonally defined behavior, nor is it related to the climatic factors evaluated, the dry season presented the highest percentages for all phenophases, which may indicate that other factors associated with the dry period may influence the trigger off the phenophases. The information collected expands the knowledge about the functioning of this ecosystem and reinforces the need for more ecological studies and reduced impact management measures, aiming at coastal vegetation conservation.