Aquatic Herbaceous Plant Research Articles

A giant gardener of the Floodplains: The Amazonian manatee

During an unusual event of extreme drought and rainfall scarcity in the Amazon in October 2023, we found 96 feces of the Amazonian manatee on the beaches of Lake Amanã (Central Amazon, Brazil). All feces contained seeds and some of them seedlings of aquatic herbaceous species, offering the opportunity to study the role of the manatee as an endozoochoric dispersal agent in the Amazonian floodplains. The feces were collected, analyzed, and the intact seeds were separated, identifying 9 morphotypes of aquatic herbaceous plants. Whole seeds were sectioned and immersed in a tetrazolium solution to assess viability of the embryos. The seeds of the species Luziola spruceana were present in all fecal samples. In 17 feces, 79 seedlings of L. sprucena, Eleocharis subarticulata, Bacopa egensis, Cyperus blepharoleptos, and Cyperus sp. were observed. The Amazon manatee migrates annually between different types of floodable environments due to the rise and fall of water levels. In these two phases of the hydrological cycle there is the availability of fruiting aquatic herbaceous plants on which it feeds. In this way, the Amazonian manatee can be considered a gardener of the Amazon floodplains, as it fertilizes the waters with nutrients that favor plant productivity and acts in the dispersal, colonization and plant succession in these environments. This fact opens a range of research opportunities and considerably elevates the importance of the manatee in the maintenance and diversity of aquatic plants, as well as in maintaining the balance of trophic chains in its living areas.

Mercury biomagnification in the food chain of a piscivorous turtle species (Testudines: Chelidae: Chelus fimbriata) in the Central Amazon, Brazil.

Due to their natural history and ecological attributes, turtles are excellent organisms for studies of heavy metal contamination. Turtles have a large geographical distribution, occupy different aquatic habitats, and occupy various trophic levels. The present study investigated mercury bioaccumulation in the carnivorous chelonian Chelus fimbriata (Matamata turtle) and Hg biomagnification in relation to its aquatic food chain in the middle Rio Negro, AM-Brazil. Tissue samples of muscle, carapace and claws were collected from 26 C. fimbriata individuals, as well as collections of autotrophic energy sources found in the turtle's aquatic habitat area. The samples were collected in February-March/2014 and analyzed for THg concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotopes. The highest THg levels were found in claws (3780 ng.g-1), carapace (3622 ng.g-1) and muscle (403 ng.g-1), which were found to be significantly different [F(2.73) = 49.02 p < 0.01]. However, THg concentrations in muscle tissue were below the consumption threshold indicated by the WHO and Brazilian Health Ministry. The average δ13C and δ15N values in Matamata samples were -31.7‰ and 11.9‰, respectively. The principal energy source sustaining the food chain of C. fimbriata was found to be terrestrial shrubs, with smaller contributions from emergent aquatic herbaceous plants and algae, while δ15N values showed its trophic position to be two levels above the autotrophic energy sources. There was a positive correlation between THg and turtle size, while a significant relationship was found between THg and δ15N, showing strong biomagnification in the food chain of C. fimbriata: y = 0.21x + 0.46; r2 = 0.45; p < 0.001, for which the slope presented a value of 0.21.

A new amino acid substitution in the MvALS1 gene of metsulfuron-methyl resistant biotypes Monochoria vaginalis (Burm. f.) C. Presl from West Java, Indonesia.

The most bothersome weed in rice fields in the Indonesian province of West Java is Monochoria vaginalis (Burm. F.) C. Presl, an aquatic herbaceous plant. Metsulfuron-methyl has long been used in wetland rice in West Java with a high enough intensity. However, the case of Monochoria vaginalis resistance to metsulfuron-methyl herbicides in Indonesia has not been widely reported and investigated. The study aims to (1) classify the resistance level of M. vaginalis toward metsulfuron-methyl, (2) identify Target Site Resistance (TSR) mechanism mutations in the MvALS1 gene of the resistant biotype of M. vaginalis. The Whole Plant Pot Test method was utilized to assess the resistance level of Monochoria vaginalis. Following that, all samples were subjected to DNA sequencing using the PCR method to identify mutations in the MvALS1 gene from the resistant biotype. After then, this study used DUET, a server with an integrated computational methodology, to anticipate the effect of mutations on protein stability. The result showed that Monochoria vaginalis from Rawamerta, Karawang showed a moderate level of resistance to metsulfuron-methyl with a resistance ratio of 6.00, Patokbeusi, Subang showed a low level of resistance to metsulfuron-methyl with a resistance ratio of 3.89, compared to susceptible Monochoria vaginalis. Nucleotide base alignment in the MvALS1 gene revealed that base substitutions occurred in the Monochoria vaginalis biotype from Rawamerta and Patokbeusi, resulting in 5 amino acid substitutions: Ser-64-Ala, Asp-66-Glu, Asn-240-Asp, Glu-426-Asn, and Ser-469-Asn and Sukra: Ser-64-Ala, Asp-66-Glu, and Asn-240-Asp. The analysis showed that S64A, D66E, and N240D stabilize the protein, whereas E426N and S469N destabilize it. This study confirms for the first time that Ser-64-Ala, Asn-240-Asp, and Glu-426-Asn amino acid mutations were found in cases of M. vaginalis resistance to metsulfuron-methyl (ALS inhibitor).

Will climate change favor exotic grasses over native ecosystem engineer species in the Amazon Basin?

Several anthropic disturbances, including deforestation, fires, the building of roads and dams, have intensified in Amazon in last decades. These disturbances contribute to an increase in the occurrence and intensity of extreme events, such as more frequent floods and more severe droughts, due to climate change. Along the Amazonian rivers, aquatic herbaceous plants, mainly of the Poaceae family, are very abundant and produce up to three times more biomass than the adjacent flooded forests, and some are considered ecosystem engineers given their structuring role in these environments. Invasive grasses have spread through the Neotropics and are gradually entering the Amazon via the Arc of Deforestation. These invasive species often attain high coverage, suppress other species, and become dominant in both disturbed and pristine habitats. The aim of this study was to establish the current and future distribution patterns of two native ecosystem engineer species (Echinochloa polystachya and Paspalum fasciculatum) and two invasive species (Urochloa brizantha and Urochloa decumbens) in the Amazon Basin. To predict the future climate, we used three scenarios, namely SSP1–2.6, SSP3–7.0 and SSP5–8.5 for the years 2040, 2080 and 2100, to project climatically suitable areas. The current climatically suitable range for the native ecosystem engineer species was estimated at 33–35% of the Amazon Basin, while the invasive ones have a range of 53–84% in potential climatically suitable areas. A decrease in the areas of suitability of the two ecosystem engineer species, E. polystachya and P. fasciculatum, was observed in all scenarios and years, while only the invasive U. brizantha showed an increase in suitable areas in all years. These results raise concerns about the invasion of grasses with high aggressive potential that could result in the exclusion of native ecosystem engineer species and their ecological roles.

Acetolactate Synthase-Inhibitor Resistance in Monochoria vaginalis (Burm. f.) C. Presl from Indonesia.

Monochoria vaginalis (Burm. f.) C. Presl, belonging to the family Pontederiaceae, is an aquatic herbaceous plant, native to temperate and tropical Asia. The species often occurs in paddy fields as a noxious weed in East Asia, and in the USA, and causes a significant reduction in rice production. The objective of the present research was the evaluation of the resistance levels of M. vaginalis against three chemical groups of acetolactate synthase (ALS)-inhibitor herbicides and other two different groups of herbicides, and the investigation of the mutations in the ALS gene of the resistant biotype of M. vaginalis. Herbicide dose–response experiments showed that the resistant biotype of M. vaginalis was highly resistant to bensulfuron-methyl, moderately resistant to bispyribac-sodium, had low resistance to penoxsulam and 2,4-D dimethyl ammonium, and was susceptible to sulfentrazone. The nucleotide sequences of the ALS gene of resistant and susceptible biotypes showed 14 base substitutions, which caused two amino acid substitutions: Val-143-Ile and Val-148-Ile. It is the first report of the substitutions of amino acids Val-143-Ile and Val-148-Ile in ALS protein. Those mutations may give different resistance spectra against three ALS-inhibitor herbicides: bensulfuron-methyl, bispyribac-sodium, and penoxsulam. Further research is needed to elucidate the molecular basis of target-site resistance mechanisms such as the transformation of the ALS gene of M. vaginalis. It is also necessary to evaluate herbicide mixtures and/or the rotation of herbicide sites of action to control the resistant biotype of M. vaginalis.

Inundation, Hydrodynamics and Vegetation Influence Carbon Dioxide Concentrations in Amazon Floodplain Lakes

Extensive floodplains and numerous lakes in the Amazon basin are well suited to examine the role of floodable lands within the context of the sources and processing of carbon within inland waters. We measured diel, seasonal and inter-annual variations of CO2 concentrations and related environmental variables in open water and flooded vegetation and estimated their habitat area using remote sensing in a representative Amazon floodplain lake, Lake Janauacá. Variability in CO2 concentrations in open water resulted from changes in the extent of inundation and exchange with vegetated habitats. Depth-averaged values of CO2 in the open water of the lake, 157 ± 91 µM (mean ± SD), were less than those in an embayment near aquatic vegetation, 285 ± 116 µM, and were variable over 24-h periods at both sites. Within floating herbaceous plant mats, the mean concentration was 275 ± 77 µM, while in flooded forests it was 217 ± 78 µM. The best statistical model that included CO2 in aquatic plant mats, water clarity, rate of change in water level and chlorophyll-a concentrations explained around 90% of the variability in CO2 concentration. Three-dimensional hydrodynamic modeling demonstrated that diel differences in water temperature between plant mats and open water as well as basin-scale motions caused lateral exchanges of CO2 between vegetated habitats and open water. Our findings extend understanding of CO2 in tropical lakes and floodplains with measurements and models that emphasize the importance of flooded forests and aquatic herbaceous plants fringing floodplain lakes as sources of CO2 to open waters.

Predicting the potential distribution of aquatic herbaceous plants in oligotrophic Central Amazonian wetland ecosystems

Aquatic herbaceous plants are especially suitable for mapping environmental variability in wetlands, as they respond quickly to environmental gradients and are good indicators of habitat preference. We describe the composition of herbaceous species in two oligotrophic wetland ecosystems, floodplains along black-water rivers (igapó) and wetlands upon hydromorphic sand soils (campinarana) in the Parque Nacional do Jaú and the Reserva de Desenvolvimento Sustentável Uatumã in Central Amazonia, both protected areas. We tested for the potential distribution range (PDR) of the most frequent species of these ecosystems, which are the ones that occurred in at least two of the sampled wetlands, using species distribution models (SDMs). In total, 98 aquatic herbaceous species were recorded, of which 63 occurred in igapós and 44 in campinaranas. Most igapó species had ample PDRs across the Neotropics, while most campinarana species were restricted to the Amazon Basin. These results are congruent with studies that described similar distribution patterns for tree and bird species, which emphasizes a high degree of endemism in Amazonian campinaranas. However, we also found differences in the potential distribution of species between the two protected areas, indicating high environmental variability of oligotrophic ecosystems that deserve further investigation to develop effective measures for their conservation and protection.

English

The versatile nature of the commercial mushroom, Pleurotus ostreatus (Jacq.: Fr.) Kumm., provides basis for continued exploration of its biochemical processes during solid state fermentation on various lignocellulosic biomass as potential substrates. As a fungal organism, P. ostreatus feeds on lignocellulose by secreting various extracellular enzymes responsible for breaking down this organic polymer into smaller and simple compounds that the hyphae can absorb to develop into mycelia. In this study, P. ostreatus was assessed for its ability to grow on Eichhornia crassipes (Mart.) Solms-Laubach., or water hyacinth biomass and possibly, utilizing it as a substrate. E. crassipes is an aquatic herbaceous plant, often branded as the world’s worst aquatic weed due to its invasive aggression, negative impact onto the aquatic ecosystems, and the cost usually associated with its control. When cultured onto the biomass of this nuisance weed followed by assessment by the agar plate-based clearing assay method and spectrophotometry, P. ostreatus demonstrated its practical ability to secrete cellulases, xylanases, pectinases, lignin peroxidases and laccases, thus showing its physiological capabilities to optionally utilize E. crassipes as a substrate. If properly optimized, this approach can be remarkably used as a sustainable and cost-effective strategy to manage E. crassipes in Zimbabwe. Key words: Pleurotus ostreatus, Eichhornia crassipes, lignocellulosic biomass, lignocellulolytic enzymes, cellulases, xylanases, pectinases, lignin peroxidases, laccases.

Evolution of the Life Forms of Flowering Plants in a Biodiversity Formation

The biomorphological diversity of riverside and aquatic herbaceous plants represented mainly by annual and biennial plants of vegetative origin, which replace perennial and biennial plants and annual, biennial, and winter monocarpics, has been studied. Depending on the season and moisture conditions, some species are represented by different basic biomorphs and phenobiomorphs. The modes of morphological evolution have been determined at the levels of individuals (abbreviations), shoots and their parts (abbreviations and the corresponding prolongations), and roots (prolongations). The role of the developmental features of monocarpic shoots in the habitat specificity of annual and biennial plants of vegetative origin has been described.

Bioinformatic identification and expression analysis of Nelumbo nucifera microRNA and their targets.

Premise of the study:Sacred lotus (Nelumbo nucifera) is a perennial aquatic herbaceous plant of ecological, ornamental, and economic importance. MicroRNAs (miRNAs) play an important role in plant development. However, reports of miRNAs and their role in sacred lotus have been limited.Methods:Using the homology search of known miRNAs with genome and transcriptome contig sequences, we employed a pipeline to identify miRNAs in N. nucifera. We also predicted the targets of these miRNAs.Results:We found 106 conserved miRNAs in N. nucifera, and 456 of their miRNA targets were annotated. Quantitative real-time PCR (qRT-PCR) analysis revealed the different expression levels of the 10 selected conserved miRNAs in tissues of young leaves, stems, and flowers of N. nucifera. Negative correlation of expression level between five miRNAs and their target genes was also revealed.Discussion:Combining bioinformatics and experiment analysis, we identified the miRNAs in N. nucifera. The results can be used as a workbench for further investigation of the roles of miRNAs in N. nucifera.

Impact of submerged herbaceous vegetation on wind-induced current in shallow water

A combined wind tunnel and water flume experiment was performed to study the effect of an aquatic herbaceous plant patch on the turbulent structure and flow field of wind-induced currents. Eel grass was chosen as the test plant. The plants were settled in patch form. Three-dimensional instantaneous velocities were measured using an acoustic doppler velocimeter (ADV). The results indicate that in the non-eel grass patch flow, turbulent shear stress −u′w′¯has a local minimum near the flow reverse point, turbulent intensity has the tendency to decrease continually from surface to bottom, and the dominant turbulent event is sweeping. In the eel grass patch with wind-induced flow, reverse flow occurs more quickly than in the non-eel grass patch case, and the reverse point shifts downward. Turbulent shear stress −u′w′¯ has two maxima below the canopy. Turbulent intensity u′2¯ decreases generally from water surface to flume bed, but there are maxima below the canopy. The dominant turbulent event is the fourth quadrant event below the canopy, and the two relative contributions of the second and the fourth quadrant event have similar values above the canopy. The mean bias and RMS values at centre of the eel grass patch are almost as two times larger as that at other measuring lines in non-eel grass region. This indicates that not only the shear stress and turbulent intensity become larger, and the vertical variations of the shear stress and turbulent intensity are also larger due to the effect of vegetation. The differences in the effects of submerged herbaceous vegetation on open channel flow and wind-induced flow were discussed in relation to time averaged velocity, turbulent shear stress, turbulent intensity and coherent structure based on the present test data and previous data.

Autochthonous primary production in southern Amazon headwater streams: Novel indicators of altered environmental integrity

The riparian forest reduces the amount of light entering streams, which limits autochthonous primary production. The aim of this study was to evaluate temporal variation of autochthonous primary production in pristine and altered streams, with the goal of identifying indicators of change in environmental integrity in the southern Brazilian Amazon. We evaluated free algal biomass in the water column, the presence of periphyton, and the richness and cover of aquatic herbaceous plants in 20 streams (10 pristine and 10 altered, i.e., with riparian deforestation) during the dry period, at the beginning of the rainy period, and at the end of the rainy period. In altered streams, we recorded the presence of macroscopic periphyton and the amount of algal biomass varied between the dry and flood seasons. Variations in hydrological periods did not contribute to changes in algal biomass in pristine streams; we did not observe the presence of macroscopic periphyton these streams. In altered streams, 23 aquatic herbaceous species were identified, versus only four in the pristine streams. Results showed that riparian deforestation contributes to increased autochthonous primary production, which is also influenced by different hydrological periods, with algae and aquatic herbaceous plants responding differently to dry and rainy periods. The responses of these primary producers confirm their role as important bioindicators of change in the environmental integrity of southern Amazonian streams.

Turbulence structure and flow field of shallow water with a submerged eel grass patch

A flume experiment was conducted to investigate the effect of the aquatic herbaceous plant patch on the turbulent structure and flow field of shallow water. The eel grass that is widely distributed in the shallow lakes in China was chosen as the targeted plant. The plants were settled in patch form with three groups of densities and flow velocities. The three-dimensional instantaneous velocities were measured using an Audio Doppler Velocitimeter (ADV). The results indicate that the vertical velocity profile in the plant patch exhibits an S-shape from the canopy to the root of the eel grass. A secondary maximum in the vertical profile of velocity near the plant root is observed. The turbulent intensity increases from the water surface to the canopy, then decreases to the plant root; there is an inflection point around canopy, where the turbulent intensity deceases from the inner region to the side boundary of the patch. The vertical profiles of the eel grass resistance coefficient CP have different forms at different positions in the patch in general, but the forms of the CP profiles are similar along the boundary of the patch, and the forms of the CP profiles are similar in the inner part of the patch. In the patch area, the turbulent flow corresponds to the Quadrant 2 event (ejection event) above the canopy, the turbulent flow corresponds to the Quadrant 4 event (sweep event) below the canopy, but near the bed the Quadrant 1 event (outward interaction), the Quadrant 2 event and the Quadrant 4 event coexist. In the lateral boundary area of the patch the Quadrant 2 event and the Quadrant 3 event (inward interaction event) coexist due to presence of a strong shear layer.

Aquatic herbaceous plants of the Amazon floodplains: state of the art and research needed

The Amazonian wetlands cover a vast area subject to a monomodal flood pulse with an annual amplitude averaging 10 m, which defines an aquatic phase and a terrestrial phase of great biological importance. According to the geological origin and the catchment areas, the physical and chemical properties of the wetland will vary, being defined two major groups, the várzeas and the igapós. Although aquatic herbaceous plants do occur in the two types, higher species richness and densities are typical of the várzeas where aquatic herbaceous species, particularly C4 plants may exhibit high biomass values and net primary production - NPP about three times these of the floodplain forest. The aquatic herbaceous plants are very important in the carbon and nutrient budgets of the várzea, since through their decomposition they promote the enrichment of the aquatic system and associated floodplains, both during the aquatic and terrestrial phases of the hydrologic cycle. The major threats to herbaceous aquatic plants are related to the modification and contamination of the habitats owing to their use in economic activities as cattle and buffalo ranching and agriculture. Degradation improves the susceptibility of these systems to fire especially during the terrestrial phase, resulting in economic losses and further degradation of floodplains. Recently oil spills linked to the petroliferous activities in the region are of major concern demanding further and urgent evaluation.

Aquatic herbaceous plants of the Amazon floodplains: state of the art and research needed

The Amazonian wetlands cover a vast area subject to a monomodal flood pulse with an annual amplitude averaging 10 m, which defines an aquatic phase and a terrestrial phase of great biological importance. According to the geological origin and the catchment areas, the physical and chemical properties of the wetland will vary, being defined two major groups, the varzeas and the igapos. Although aquatic herbaceous plants do occur in the two types, higher species richness and densities are typical of the varzeas where aquatic herbaceous species, particularly C4 plants may exhibit high biomass values and net primary production - NPP about three times these of the floodplain forest. The aquatic herbaceous plants are very important in the carbon and nutrient budgets of the varzea, since through their decomposition they promote the enrichment of the aquatic system and associated floodplains, both during the aquatic and terrestrial phases of the hydrologic cycle. The major threats to herbaceous aquatic plants are related to the modification and contamination of the habitats owing to their use in economic activities as cattle and buffalo ranching and agriculture. Degradation improves the susceptibility of these systems to fire especially during the terrestrial phase, resulting in economic losses and further degradation of floodplains. Recently oil spills linked to the petroliferous activities in the region are of major concern demanding further and urgent evaluation.

Estabelecimento de Echinochloa polystachya (H.B.K.) Hitchcock (Poaceae) em solo de várzea contaminado com petróleo de Urucu

A utilização de plantas para fitorremediação do solo requer que a concentração do poluente esteja dentro dos limites de tolerância da planta para que o tratamento seja eficaz. O rebrotamento e crescimento da herbácea aquática Echinochloa polystachya em solo de várzea contaminado por petróleo de Urucu foram estudados por meio do plantio de propágulos em frascos com 2 L de solo contaminado pela mistura de 7 dosagens de petróleo, distribuídas entre 0 e 0,46 L m-2. O experimento foi realizado em Casa de Vegetação e as plantas foram monitoradas durante 70 dias. Em resposta ao aumento da dosagem do petróleo, houve diminuição da biomassa aérea, da proporção de biomassa aérea viva/aérea total, do comprimento da folha e do número de folhas. A interação entre dosagem e tempo de exposição levou à diminuição do número de folhas, comprimento da folha, altura de inserção da primeira folha e aumento do número de folhas com comprometimento fitossanitário. A utilização de E. polystachya para fitorremediação pode estar limitada a solos com baixas dosagens de petróleo de Urucu.

Antioxidant and antiatherogenic activity ofcis-hinokiresinol fromTrapa pseudoincisa

cis-Hinokiresinol, also known as (+)-nyasol, was isolated for the first time from an aquatic herbaceous plant, Trapa pseudoincisa NAKAI, via silica gel and octadecyl silica gel column chromatographies. The chemical structure was determined via analyses of the spectroscopic data, including NMR, MS and IR. cis-Hinokiresinol was also found to exhibit antioxidant and antiatherogenic activities. The ICso values for the scavenging activities of cis-hinokiresinol on ABTS cation and superoxide anion radicals were 45.6 and 40.5 microM, respectively. The IC50 values for the inhibitory effects on Lp-PLA2, hACAT1, hACAT2 and LDL-oxidation were 284.7, 280.6, 398.9 and 5.6 microM, respectively.

PERMAFROST DEGRADATION AND ECOLOGICAL CHANGES ASSOCIATED WITH A WARMING CLIMATE IN CENTRAL ALASKA

Studies from 1994-1998 on the Tanana Flats in central Alaska reveal that permafrost degradation is widespread and rapid, causing large shifts in ecosystems from birch forests to fens and bogs. Fine-grained soils under the birch forest are ice-rich and thaw settlement typically is 1- 2.5 m after the permafrost thaws. The collapsed areas are rapidly colonized by aquatic herbaceous plants, leading to the development of a thick, floating organic mat. Based on field sampling of soils, permafrost and vegetation, and the construction of a GIS database, we estimate that 17% of the study area (263,964 ha) is unfrozen with no previous permafrost, 48% has stable permafrost, 31% is partially degraded, and 4% has totally degraded. For that portion that currently has, or recently had, permafrost (83% of area),42% has been affected by thermokarst development. Based on airphoto analysis, birch forests have decreased 35% and fens have increased 29% from 1949 to 1995. Overall, the area with totally degraded permafrost (collapse-scar fens and bogs) has increased from 39 to 47% in 46 y. Based on rates of change from airphoto analysis and radiocarbon dating, we estimate 83% of the degradation occurred before 1949. Evidence indicates this permafrost degradation began in the mid-1700s and is associated with periods of relatively warm climate during the mid-late 1700s and 1900s. If current conditions persist, the remaining lowland birch forests will be eliminated by the end of the next century.