Insecticidal efficacy and possibility of Combretum trifoliatum Vent. (Myrtales: Combretaceae) extracts in controlling Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).

BACKGROUND: The fall armyworm Spodoptera frugiperda (J.E. Smith), is an important pest of agronomical crops. It is interesting to discover secondary metabolites in plants that are environmentally safer than synthetic pesticides. For this purpose, Combretum trifoliatum crude extract and its isolated compounds were investigated for their insecticidal activities against S. frugiperda. RESULTS: The median lethal dose (LD50 ) was evaluated in the second-instar larvae using the topical application method. The isolated compounds, apigenin and camphor, demonstrated a highly toxic effect on larvae at a lower LD50 dose than crude extract. Moreover, when the larvae were exposed to crude extract concentrations, the development to pupa and adult stages was reduced by more than 50%. The ovicidal toxicity was examined using a hand sprayer. The extract concentration 5, 10, and 20 µg/egg significantly decreased the egg hatchability. In addition, crude extract showed a significant difference in inhibiting acetylcholinesterase (AChE) activity while crude extract and camphor showed significant inhibitory effects on carboxylesterase (CE) and glutathione-S-transferase (GST) activities. CONCLUSION: The crude ethanol extract of Combretum trifoliatum was toxic to S. frugiperda in terms of larval mortality, negatively affecting biological parameters, and decreasing egg hatchability. Additionally, the activities of cholinergic and detoxifying enzymes were affected by crude extract and its isolated compounds. These results highlight that Combretum trifoliatum might be efficient as a bioinsecticide to control S. frugiperda. © 2023 Society of Chemical Industry.

The remediation of drought stress under VAM inoculation through proline chemical transformation action.

This article discussed the enhanced drought tolerance under arbuscular mycorrhizal (AM) inoculation and normal growth of plants which linked with the activity of photoreceptors. The photoreceptor action in dual symbiosis under drought stress showed not only the high photosynthetic activity but also provide information about the broad range of physiological responses. The pot experiment conducted in a natural environment where drought condition was observed twice a week via regular irrigation with water up to twelve months. Plants analysis showed the high contents of water, hydrogen peroxide, carotenoids, proline, antioxidant enzymes like super dismutase (SOD) and catalase(CAT) in both leaves and roots with a large surface area of leaves over control. The elevated concentration of hydrogen peroxide (0.04 ±â€¯0.0 µmol/g) coupled with singlet oxygen species was the main modified molecular mechanism which was operative in drought condition. The accretion of proline under drought stress in dual symbiosis (32.3 ±â€¯0.3 µg/mL) was related to the highest branching pattern of young leaves and the chemical transformation of reactive oxygen species (ROS) including H2O2 and 3O2 into useful molecules like water and triplet molecular oxygen. The higher contents of carotenoids (5.0 ±â€¯1.2 mg/g) in drought over control (4.8 ±â€¯1.6 mg/g) and AM plant (4.9 ±â€¯1.2 mg/g) was found to be supportive in the conversion of singlet oxygen into triplet one.

The potential of an energy crop "Conocarpus erectus" for lead phytoextraction and phytostabilization of chromium, nickel, and cadmium: An excellent option for the management of multi-metal contaminated soils.

Past studies have thoroughly explored the phytoextraction/phytostabilization potentials of different plant species for particular metals. However, none of the plants was able to tackle the problem of multi-metal in contaminated soils. We report herewith the potential of Conocarpus erectus to extract lead (Pb) while having the capability to stabilize chromium (Cr), nickel (Ni) and cadmium (Cd) in polluted soil. The C. erectus was subjected to grow for 120 days in a soil spiked with four different levels of each metal i.e. Pb (0, 600, 1200 and 2400 mg kg-1), Ni (0, 50, 100 and 200 mg kg-1), Cr (0, 150, 300 and 600 mg kg-1) and Cd (0, 20, 40 and 80 mg kg-1). Data related to plant growth, physiology, biochemistry and antioxidants activities revealed that forenamed parameters were significantly reduced with increasing spiking levels. Contrarily, metal speciation in plant parts (metal concentrations in shoots and roots, and metal contents in these corresponding plant parts), metal removal per pot, and DTPA-extractable metals from the soil were significantly increased with increasing spiking level upon the termination of the experiment. Curiously, each spiking level demonstrated elevated Pb concentrations in shoots than roots, while the concentrations of other metals (Cr, Ni, and Cd) were found higher in roots than in the shoots. Likewise, at each spiking level, C. erectus showed both bioconcentration factor (BCF) and translocation factor (TF) values greater than 1 for Pb, while these values were ever lower than 1 for Cr, Ni, and Cd. Moreover, the percentages of Pb removal were ever higher than other metals at each spiking level. Outcomes of our experiment suggest that C. erectus has immense potential for the phytoextraction of Pb and phytostabilization of Cr, Ni, and Cd in polluted soil. It is suggested that this plant can be used to tackle the problem of multi-metal pollution in soils.

New Prospective for Enhancement in Bioenergy Resources Through Fungal Engineering.

BACKGROUND: Lignin and cellulose, organic constituents of the plant or plant-based material not commonly used for feeding purpose are referred as Biomass. Patents suggest that this can be used as the best resource of renewable energy. Vesicular Arbuscular Mycorrhizae (VAM) fungi can play an effective role in biomass manufacturing through activated metabolism of the plant under dual symbiosis. During C acclimatization, mycorrhizal inoculated plants existent greater number of leaves with a height of plants as compared to non-mycorrhizal plants. The current article discloses the search of the natural resources for C assimilation into biomass using mycorrhizal symbiosis. METHODS: The pot experiment was conducted in the natural environment for extraction of more bioenergy through biomass of Conocarpus erectus L under VAM (Glomus fasciculatum) inoculation in various environmental conditions with replicates. RESULTS: It observed that these fungal engineered plants showed distinctive prospective to offer, enhanced biomass to energy couple with a strong network for sinking CO2 from the atmosphere via strong roots and large surface area of leaves. There was an increase in biomass (9-17% respectively) of the plant under drought-VAM, VAM inoculation and VAM- enriched CO2 conditions in same period in comparison to control plants through lignin, cellulose and carbohydrate contents. It was followed by enhanced enzyme activities and nutrient ions in dual symbiosis. CONCLUSION: Coupling biomass-originated energy may recover environmental conditions and commercial value for sustainable growth in energy consumption sector. The green energy from fungal engineered plants may replace high demand of fossil fuel as a young biofuel and make the cities more productive in the fabrication of bioenergy too in the form of biomass or biofuel with C impartial atmosphere.

Antiproliferation and antibacterial effect of biosynthesized AgNps from leaves extract of Guiera senegalensis and its catalytic reduction on some persistent organic pollutants.

The study concentrate on the biosynthesis of silver nanoparticles (AgNps) from the leaves extract of Guiera senegalensis with focus on its; antiproliferation effect on prostate (PC3), breast (MCF7) and liver (HepG2) cancer cell lines, antibacterial effect on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) and the degradation on 4-nitrophenol (4-NP) and congo red dye (CR). The synthesized AgNps were characterized by FTIR, TEM, FESEM, XRD and EDX analysis. The EDS spectrum revealed that the synthesized nanoparticles (Nps) were composed of 55.45% Ag atoms of spherical shape with approximately 50nm size, identified from TEM and FESEM data. The antiproliferation effect of the AgNps varies with cell lines in a concentration dependent manner. The result showed that the AgNps were more effective on PC3 (IC50 23.48µg/mL) than MCF7 (29.25µg/mL) and HepG2 (33.25µg/mL) by the virtue of their IC50 values. The AgNps were highly effective against E. coli and S. aureus by killing 99% colonies. The AgNps also shows a good catalytic reduction of the toxic organic pollutants in which only 3mg of the AgNps degraded 95% of both CR dye and 4-NP in 22 and 36min respectively. Therefore, the green synthesis of AgNps may have potential applications in pharmacology and industries for the treatment of cancers, bacterial infections and in degrading toxic organic pollutants in water.

Diagnosing the level of stress on a mangrove species (Laguncularia racemosa) contaminated with oil: A necessary step for monitoring mangrove ecosystems.

Monitoring the effects of pollution on mangrove vegetation is a challenge. A specific study using an oil spill simulation on mangrove species was conducted to address this challenge. We tested the effectiveness of the chlorophyll a fluorescence kinetics as a fast and robust method to diagnose the vitality of Laguncularia racemosa. We used L. racemosa plants contaminated with marine fuel oil in mangrove microcosm models. Several parameters of the JIP-test were capable of detecting the impairment of the photosynthetic function prior to the visual manifestation of symptoms in response to oil contamination. The results support the use of the chlorophyll fluorescence transient as a reliable, fast and easy to apply diagnostic method for evaluating oil-impacted mangroves. To the best of our knowledge, it is the first time that consistent data showing photosynthetic impairment in response to oil contamination is shown for a mangrove tree species.

One-pot biogenic fabrication of silver nanocrystals using Quisqualis indica: Effectiveness on malaria and Zika virus mosquito vectors, and impact on non-target aquatic organisms.

Currently, mosquito vector control is facing a number of key challenges, including the rapid development of resistance to synthetic pesticides and the recent spread of aggressive arbovirus outbreaks. The biosynthesis of silver nanoparticles (AgNPs) is currently considered an environmental friendly alternative to the employ of pyrethroids, carbamates and microbial agents (e.g. Bacillus thuringiensis var. israelensis), since AgNPs are easy to produce, effective and stable in the aquatic environment. However, their biophysical features showed wide variations according to the botanical agent using for the green synthesis, outlining the importance of screening local floral resources used as reducing and stabilizing agents. In this study, we focused on the biophysical properties and the mosquitocidal action of Quisqualis indica-fabricated AgNPs. AgNPs were characterized using spectroscopic (UV, FTIR, XRD) and microscopic (AFM, SEM, TEM and EDX) techniques. AFM, SEM and TEM confirmed the synthesis of poly-dispersed AgNPs with spherical shape and size ranging from 1 to 30nm. XRD shed light on the crystalline structure of these AgNPs. The acute toxicity of Quisqualis indica extract and AgNPs was evaluated against malaria, arbovirus, and filariasis vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus, as well as on three important non-target aquatic organisms. The Q. indica leaf extract showed moderate larvicidal effectiveness on Cx. quinquefasciatus (LC50=220.42), Ae. aegypti (LC50=203.63) and An. stephensi (LC50=185.98). Q. indica-fabricated AgNPs showed high toxicity against Cx. quinquefasciatus (LC50=14.63), Ae. aegypti (LC50=13.55) and An. stephensi (LC50=12.52), respectively. Notably, Q. indica-synthesized AgNPs were moderately toxic to non-target aquatic mosquito predators Anisops bouvieri (LC50=653.05µg/mL), Diplonychus indicus (LC50=860.94µg/mL) and Gambusia affinis (LC50=2183.16µg/mL), if compared to the targeted mosquitoes. Overall, the proposed one-pot biogenic fabrication of AgNPs using Q. indica is a low-cost and eco-friendly tool in the fight against Zika virus, malaria and filariasis vectors, with little impact against non-target aquatic mosquito predators.

Differential bioaccumulation and translocation patterns in three mangrove plants experimentally exposed to iron. Consequences for environmental sensing.

Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle were experimentally exposed to increasing levels of iron (0, 10, 20 and 100 mg L(-1) added Fe(II) in Hoagland's nutritive medium). The uptake and translocation of iron from roots to stems and leaves, Fe-secretion through salt glands (Avicennia schaueriana and Laguncularia racemosa) as well as anatomical and histochemical changes in plant tissues were evaluated. The main goal of this work was to assess the diverse capacity of these plants to detect mangroves at risk in an area affected by iron pollution (Vitoria, Espírito Santo, Brazil). Results show that plants have differential patterns with respect to bioaccumulation, translocation and secretion of iron through salt glands. L. racemosa showed the best environmental sensing capacity since the bioaccumulation of iron in both Fe-plaque and roots was higher and increased as the amount of added-iron rose. Fewer changes in translocation factors throughout increasing added-iron were observed in this species. Furthermore, the amount of iron secreted through salt glands of L. racemosa was strongly inhibited when exposed to added-iron. Among three studied species, A. schaueriana showed the highest levels of iron in stems and leaves. On the other hand, Rhizophora mangle presented low values of iron in these compartments. Even so, there was a significant drop in the translocation factor between aerial parts with respect to roots, since the bioaccumulation in plaque and roots of R. mangle increased as iron concentration rose. Moreover, rhizophores of R. mangle did not show changes in bioaccumulation throughout the studied concentrations. So far, we propose L. racemosa as the best species for monitoring iron pollution in affected mangroves areas. To our knowledge, this is the first detailed report on the response of these plants to increasing iron concentration under controlled conditions, complementing existing data on the behavior of the same plants under field exposure.

Effect of pollution by particulate iron on the morphoanatomy, histochemistry, and bioaccumulation of three mangrove plant species in Brazil.

In Brazil, some mangrove areas are subjected to air pollution by particulate iron from mining activities. However, the effect of this pollutant on mangrove plants is not well known. This study aimed to comparatively analyze the morphoanatomy, histochemistry, and iron accumulation in leaves of Avicennia schaueriana, Laguncularia racemosa, and Rhizophora mangle. Samples were collected from five mangrove sites of Espírito Santo state, each of which is exposed to different levels of particulate iron pollution. The amount of particulate material settled on the leaf surface was greater in A. schaueriana and L. racemosa, which contain salt glands. High iron concentrations were found in leaves of this species, collected from mangrove areas with high particulate iron pollution, which suggests the foliar absorption of this element. None of the samples from any of the sites showed morphological or structural damage on the leaves. Scanning electron microscopy (SEM) coupled to X-ray diffraction rendered a good method for evaluating iron on leaves surfaces. A histochemical test using Prussian blue showed to be an appropriate method to detect iron in plant tissue, however, proved to be an unsuitable method for the assessment of the iron bioaccumulation in leaves of A. schaueriana and R. mangle. So far, this study demonstrates the need of evaluating the pathway used by plants exposed to contaminated particulate matter to uptake atmospheric pollutants.

Nutrient removal in a closed silvofishery system using three mangrove species (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle).

The removal of ammonium (NH4(+)), nitrite (NO2(-)), nitrate (NO3(-)), and phosphate (PO4(-3)) in a closed silvofishery system was examined using three mangrove species (i.e., Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle). Specifically, six closed tanks were installed for this experiment with a population of 60 Dormitator latifrons fishes per tank. We planted 40 seedlings in each of three experimental tanks separated by species, while the remaining tanks were used as control. During 15 weeks, nutrient concentrations among the three mangrove systems presented no significant differences (P>0.05). However, nutrient removal variability was minimum during the last 2-5 weeks. Mangroves presented an average efficiency of 63% for the removal of NH4(+) and NO2(-). Contrary, the average removal potential of NO3(-) and PO4(-3) was 50%. Results from this study suggest that the three mangrove species could be used in a closed silvofishery systems for the biological removal of NH4(+), NO2(-), NO3(-), and PO4(-3).

Secondary metabolites and nutrients of woody plants in relation to browsing intensity in African savannas.

Carbon-based secondary metabolites (CBSMs) are assumed to function as defences that contribute to herbivore-avoidance strategies of woody plants. Severe browsing has been reported to reduce concentrations of CBSMs and increase N concentrations in individual plants, causing heavily browsed plants to be characterised by N-rich/C-poor tissues. We hypothesised that concentrations of condensed tannins (CT) and total polyphenols (TP) should decrease, or N increase, in relation to increasing intensity of browsing, rendering severely browsed plants potentially more palatable (increased N:CT) and less N-limited (increased N:P) than lightly browsed ones. We sampled naturally browsed trees (taller than 2 m) of four abundant species in southern Kruger National Park, South Africa. Species-specific relationships between N:CT, CT, TP and P concentrations and increasing browsing intensity were detected, but N and N:P were consistently invariable. We developed a conceptual post-hoc model to explain diverse species-specific CBSM responses on the basis of relative allocation of C to total C-based defence traits (e.g. spines/thorns, tough/evergreen leaves, phenolic compounds). The model suggests that species with low allocation of C to C-based defence traits become C-limited (potentially more palatable) at higher browsing intensity than species with high allocation of C to C-based defences. The model also suggests that when N availability is high, plants become C-limited at higher browsing intensity than when N availability is low.

Effect of different dietary levels of mangrove (Laguncularia racemosa) leaves and spice supplementation on productive performance, egg quality, lipid metabolism and metabolic profiles in laying hens.

In order to study the influence of white mangrove (Laguncularia racemosa) leaves on productive performance, egg quality, lipids metabolism and metabolic profiles, 180 Hy-line laying hens were randomly distributed to 6 dietary treatments each contained 6 replicates of 5 individually caged hens during the period from 50 to 60 weeks of age. 2. Three isoenergetic and isonitrogenous diets were formulated to contain 0, 50 and 100 g/kg of sun-dried mangrove leaves. Each diet was fed with or without supplementation of 2 g of cardamom, cumin, hot and black pepper mixture (1:1:1:1)/kg diet. 3. Mangrove leaves at either 50 or 100 g/kg adversely affect laying rate, egg mass and FCR, whilst increasing water intake and water to feed ratio. Mangrove leaves had no significant effect on dry matter, protein, lipid, cholesterol and ash content of liver, or on dry matter, protein and ash of yolk. 4. Plasma total protein, total lipids; liver enzymes AST and ALT and mortality rate were not significantly affected by mangrove leaves. On the other hand, yolk lipid, yolk cholesterol and plasma cholesterol significantly decreased, while yolk colour significantly increased with inclusion of 50 or 100 g/kg mangrove leaves, and Haugh unit score significantly increased with 100 g/kg mangrove leaves. 5. Spice mixture significantly increased egg weight by 2.2%. Yolk lipid content significantly decreased by 2.6%, while yolk colour and Haugh unit significantly increased with inclusion of spice mixtures. 6. In conclusion, mangrove leaves at 50 g/kg may be included in the laying hen diets as a means of decreasing lipid and cholesterol in yolk and plasma cholesterol and increasing yolk colour. Spice mixture at 2 g of cardamom, cumin, hot and black pepper mixture (1:1:1:1)/kg diet increased laying rate, egg mass, Haugh unit score and yolk colour while decreasing yolk lipids.

Hepatoprotective evaluation of Anogeissus latifolia: in vitro and in vivo studies.

AIM: To evaluate the hepatoprotective activity of a hydroalcoholic extract of the bark of Anogeissus latifolia; in vitro in primary rat hepatocyte monolayer culture and in vivo in the liver of Wistar rats intoxicated by carbon tetrachloride (CCl(4)). METHODS: In the in vitro study, a primary hepatocyte monolayer culture was treated with CCl(4) and extract of Anogeissus latifolia. Hepatoprotective activity was demonstrated in the CCl(4) damaged primary monolayer culture. In the in vivo study, the hepatoprotective activity of a hydroalcoholic extract of Anogeissus latifolia was analyzed in liver injured CCl(4)-treated rats. Biochemical parameters including serum transaminases [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)] and alkaline phosphatase (ALP) in serum were analyzed. The biochemical findings were supplemented with histopathological examination of rat liver sections. RESULTS: In vitro: primary hepatocyte monolayer cultures were treated with CCl(4) and extract of Anogeissus latifolia. A protective activity could be demonstrated in the CCl(4) damaged primary monolayer culture. In vivo: Hydroalcoholic extract of Anogeissus latifolia (300 mg/kg) was found to have protective activity in rats with CCl(4)-induced liver damage as judged from serum marker enzyme activity. CONCLUSION: The above findings lead to the conclusion that the hydroalcoholic extract of Anogeissus latifolia is hepatoprotective. Hence, we suggest that the inclusion of this plant in the management of liver disorders is justified.

Dial organic carbon fluctuations in a mangrove tidal creek in Sepetiba bay, Southeast Brazil

The carbon (C) concentration and flux, as dissolved organic carbon (DOC), particulate organic carbon (POC) and macrodetritus (MD), were quantified through 4 tidal cycles in a mangrove tidal creek in Southeastern Brazil. DOC was the major fraction of the total C concentration, accounting for 68 and 61 percent of the total C concentration during ebb and flood periods respectively. Concentrations of DOC (Ebb = 3,41 ± 0,57 mgC.L-1 and Flood = 3,55 ± 0,76 mgC.L-1) and POC (Ebb = 1,73 ± 0,99 mgC.L-1 and Flood = 1,28 ± 0,45 mgC.L-1) were relatively similar during the four tidal cycles. Macrodetritus presented a wide variation with concentration peaks probably related to external forces, such as winds, which enrich the ebb flow with leaf litter. DOC and POC fluxes depended primarily on tidal and net water fluxes, whereas MD fluxes were not. The magnitude of the DOC and POC fluxes varied with the area flooded at high tide, but not the MD fluxes. DOC was the major form of carbon export to Sepetiba Bay. During the four tidal cycles, the forest exported a total of 1,2 kg of organic carbon per ha, mostly as DOC (60 percent), followed by POC (22 percent) and MD (18 percent).

As concentrações e fluxos de carbono orgânico sob forma de carbono orgânico dissolvido (COD), carbono orgânico particulado (COP) e macrodetritos (MD) foram quantificadas durante 4 ciclos de maré em canal de maré na Floresta Experimental de Itacuruçá, Baía de Sepetiba, RJ, litoral sudeste do Brasil. COD foi a fração mais importante para a concentração total de carbono orgânico, contribuindo com 68 e 61 por cento da concentração total de C nos períodos de maré vazante e enchente, respectivamente. As concentrações de COD (vazante = 3.41 ± 0.57 mgC.L-1 e enchente = 3.55 ± 0.76 mgC.L-1) e COP (vazante = 1.73 ± 0.99 mgC.L-1 e enchente = 1.28 ± 0.45 mgC.L-1) foram similares durante os 4 ciclos de maré. A fração macrodetritos apresentou uma ampla variabilidade com máximos de concentração relacionados a fatores externos como ventos, que enriqueceram as águas de vazante com macrodetritos. A magnitude dos fluxos de COD e COP, mas não os de macrodetritos, relacionaram-se com os fluxos de água e a conseqüente área inundada pela maré. A fração COD foi a mais importante forma de exportação de carbono orgânico pelo manguezal. Durante os 4 ciclos monitorados, a floresta exportou um total de 1.2 kg de carbono orgânico, 60 por cento sob forma de COD, seguido pelo COP (22 por cento) e pela fração macrodetritos (18 por cento).

Dial organic carbon fluctuations in a mangrove tidal creek in Sepetiba bay, Southeast Brazil.

The carbon (C) concentration and flux, as dissolved organic carbon (DOC), particulate organic carbon (POC) and macrodetritus (MD), were quantified through 4 tidal cycles in a mangrove tidal creek in Southeastern Brazil. DOC was the major fraction of the total C concentration, accounting for 68 and 61% of the total C concentration during ebb and flood periods respectively. Concentrations of DOC (Ebb = 3.41 +/- 0.57 mgC.L-1 and Flood = 3.55 +/- 0.76 mgC.L-1) and POC (Ebb = 1.73 +/- 0.99 mgC.L-1 and Flood = 1.28 +/- 0.45 mgC.L-1) were relatively similar during the four tidal cycles. Macrodetritus presented a wide variation with concentration peaks probably related to external forces, such as winds, which enrich the ebb flow with leaf litter. DOC and POC fluxes depended primarily on tidal and net water fluxes, whereas MD fluxes were not. The magnitude of the DOC and POC fluxes varied with the area flooded at high tide, but not the MD fluxes. DOC was the major form of carbon export to Sepetiba Bay. During the four tidal cycles, the forest exported a total of 1.2 kg of organic carbon per ha, mostly as DOC (60%), followed by POC (22%) and MD (18%).

Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod.

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation-light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings.

Five biflavonoids from Calycopteris floribunda (Combretaceae).

The structures of five biflavonoids, 6"-demethoxyneocalycopterone (1), calyflorenone C (2), 6"-epi-calyflorenone B (3), 6"-epi-calyflorenone C (4) and calyflorenone D (5) from the green parts of Calycopteris floribunda were established by NMR and MS. Their NMR and chiroptical properties (CD, [alpha]20D ) were compared with those of the known C. f. biflavonoids 6-11. Compound 1 represents a calycopterone derivative, 2-5 have a calyflorenone skeleton. With regard to one chiral center (C-6"), 4 and 3 are the respective epimers of 2 and 11.