Mangrove Avicennia Marina Research Articles

Accumulation of trace metals in grey mangrove Avicennia marina fine nutritive roots: The role of rhizosphere processes

Mangrove sediment has long been recognized as being important in restricting the mobility of contaminants in estuarine environments. To investigate the role of rhizosphere processes in the accumulation of trace metals in mangrove fine nutritive roots, the mangrove sediments and associated fine nutritive roots are collected from five major embayments of Sydney estuary (Australia) for geochemical studies. In this estuary Avicennia marina sediments are accumulating large quantities of trace metals due to presence of abundant fine sediment (<62.5μm) and organic matter as well as anthropogenic input. Accumulation of trace metals in fine nutritive roots responds to total sediment chemistry mainly due to rhizosphere sediment geochemical processes resulting in a strong linear correlation between metal concentrations in fine nutritive roots vs. total and bio-available contents in sediments. Accumulation of trace metals in fine nutritive roots is almost always exceeds rhizosphere total sediment metal concentrations.

Ecophysiological responses of the mangrove Avicennia marina to trace metal contamination

Growth responses of Avicennia marina seedlings to contamination by different concentrations of two essential (Cu, Zn) and two non-essential (Pb, Hg) trace metals were studied under glasshouse conditions. We tested the hypothesis that soil retention and root ultrafiltration would exclude most of the trace metals, and that those that are absorbed and translocated to the shoots would interfere with plant performance and be excreted via leaf salt glands. One-month-old seedlings were subjected to Cu, Zn, Pb and Hg at concentrations of 0, 40, 80, 120 and 160μgg−1 sediment for 12 months in a randomized complete block design (n=6). Photosynthesis was measured at the end of 12 months of trace metal exposure with a portable gas exchange system and chlorophyll fluorescence with a pulse-modulated fluorometer. After morphometric measurements, plants were harvested and analyzed for Cu, Zn, Pb and Hg by atomic absorption spectroscopy. Total dry biomass decreased with increasing trace metal concentration for all metals. In the 160μgg−1 Cu, Zn, Hg and Pb treatments, total biomass was significantly lower than the control value by 43%, 37%, 42% and 40%, respectively. Decreases in plant height and number of leaves followed trends similar to those for total biomass and ranged from 37% to 60%, compared to the controls. Decreases in chlorophyll content in the trace metal treatments ranged from 50% to 58% compared to the control. Carbon dioxide exchange, quantum yield of photosystem II (PSII), electron transport rate (ETR) through PSII and photosynthetic efficiency of PSII (Fv/Fm) were highest in the control treatment and decreased with increasing trace metal concentrations. Decreases in CO2 exchange in the 160μgg−1 treatments for all trace metals ranged from 50% to 60%. Concentrations of all trace metals in plant organs increased with increasing metal concentrations and were higher in roots than in shoots, with concentrations of Cu and Zn being considerably higher than those of Hg and Pb. Qualitative elemental analyses and X-ray mapping of crystalline deposits over the glands at the leaf surfaces indicated that Cu and Zn were excreted from the salt glands, while Hg and Pb were absent, at least being below the limits of detection. These results demonstrate that growth processes are sensitive to trace metals and therefore can be considered as a cost of metal tolerance, but salt glands of this mangrove species do contribute eliminating at least part of physiologically essential trace metals if taken up in excess.

Radiocarbon dating and wood density chronologies of mangrove trees in arid Western Australia.

Mangrove trees tend to be larger and mangrove communities more diverse in tropical latitudes, particularly where there is high rainfall. Variation in the structure, growth and productivity of mangrove forests over climatic gradients suggests they are sensitive to variations in climate, but evidence of changes in the structure and growth of mangrove trees in response to climatic variation is scarce. Bomb-pulse radiocarbon dating provides accurate dates of recent wood formation and tree age of tropical and subtropical tree species. Here, we used radiocarbon techniques combined with X-ray densitometry to develop a wood density chronology for the mangrove Avicennia marina in the Exmouth Gulf, Western Australia (WA). We tested whether wood density chronologies of A. marina were sensitive to variation in the Pacific Decadal Oscillation Index, which reflects temperature fluctuations in the Pacific Ocean and is linked to the instrumental rainfall record in north WA. We also determined growth rates in mangrove trees from the Exmouth Gulf, WA. We found that seaward fringing A. marina trees (∼10 cm diameter) were 48±1 to 89±23 years old (mean ± 1σ) and that their growth rates ranged from 4.08±2.36 to 5.30±3.33 mm/yr (mean ±1σ). The wood density of our studied mangrove trees decreased with increases in the Pacific Decadal Oscillation Index. Future predicted drying of the region will likely lead to further reductions in wood density and their associated growth rates in mangrove forests in the region.

Identifying the Real Pollinators? Exotic Honeybees Are the Dominant Flower Visitors and Only Effective Pollinators of Avicennia marina in Australian Temperate Mangroves

The literature suggests that, in the tropics, mangroves are typically pollinated by a range of generalist pollinators, whereas in temperate populations, pollination biology is largely unstudied. We predicted that, for the mangrove Avicennia marina in temperate southeast Australia, pollinator diversity would be low and its pollination system modified by the exotic honeybee Apis mellifera. Multiyear surveys and experiments were used to test these hypotheses by determining the identity and frequency of flower visitors, quantifying pollinator foraging behaviour, determining the species composition of pollen loads, and demonstrating pollen removal and deposition. We identified 38 species that visited flowers, but only A. mellifera was a significant pollinator. It was the only species to carry large amounts of pollen and forage in a manner permitting transfer of pollen to stigmas. Moreover, A. mellifera was the numerically dominant flower visitor and was effective in both pollen removal and deposition. This study demonstrates the importance of distinguishing flower visitors from pollinators and emphasises the surprisingly widespread influence of the exotic A. mellifera. Finally, our study and a worldwide review of the literature on the pollination of mangroves reveal that the pollination biology of other mangrove systems requires similar scrutiny.

Mangrove (Avicennia marina subsp. australasica) litter production and decomposition in a temperate estuary

Mangrove forests can provide important cross-boundary subsidies of organic matter to adjacent habitats through the production, export, decomposition and assimilation of litter. We quantified two of these components in a temperate mangrove forest in Whangamata Harbour, New Zealand: 1) litter production; and 2) decomposition rates as a function of tidal elevation, sediment type and burial depth. Litter traps sampled monthly for a year measured an annual detrital input of 3.24–5.38 t DW ha−1, of which 77% occurred in summer. Decomposition rates depended on litter type, with leaves decomposing faster (63 d to decay by 50%) than pneumatophore and wood material (316 and 460 d, respectively). Buried leaf and wood litter decomposed 1.3–1.4 times slower than litter on the sediment surface; however, tidal elevation and sediment type (mud vs. sand) had no effect. The slow decay of litter (an order of magnitude slower than tropical mangrove litter) suggests that its incorporation into temperate marine food webs may be relatively slow.

Positive correlation between salinity and n-alkane δ13C values in the mangrove Avicennia marina

Carbon isotope ratio (δ13C) values of lipid biomarkers from plants can be used to assess water use efficiency and to reconstruct environmental conditions in the past. We assessed the effect of salinity on the δ13C values for leaf wax n-C31 and n-C33 alkanes, bulk leaf matter and leaf total lipid extracts from Avicennia marina (gray mangrove) trees growing along the Brisbane River estuary in Queensland, Australia. We observed an increase in 0.19±0.053‰ (R2 0.61, p 0.008) and 0.16±0.052‰ (R2 0.55, p 0.01) per salinity unit for the two n-alkanes, respectively, and of 0.087±0.028‰ (R2 0.41, p 0.009) for whole leaves per salinity unit, indicating that water use efficiency of A. marina increased with the salt content of water. There was no correlation between δ13C values of total lipid extracts and salinity, perhaps because of a decrease in lipid concentration at higher salinity or because of varying contributions of different lipid classes to the extract. The robust relationship between salinity and δ13C values of leaf wax lipids provides a means of quantitatively reconstructing past salinity from carbon isotope ratios of mangrove lipid biomarkers in sediments. When paired with measurements of the hydrogen isotope ratio values of the same compounds, the approach should facilitate quantitative reconstruction of the hydrogen isotope composition of environmental water. In order for the method to successfully reconstruct past salinity and water isotopes, a mangrove source for leaf wax would need to be confirmed by palynological or other evidence, or the isotopic composition of a more source specific biomarker, such as taraxerol, would need to be measured.

Adenosine deaminase production by an endophytic bacterium (Lysinibacillus sp.) from Avicennia marina.

The present study was carried out with the following objectives: (1) to isolate the endophytic bacilli strains from the leaves of mangrove plant Avicennia marina, (2) to screen the potential strains for the production of adenosine deaminase, (3) to statistically optimize the factors that influence the enzyme activity in the potent strain, and (4) to identify the potent strain using 16S rRNA sequence and construct its phylogenetic tree. The bacterial strains isolated from the fresh leaves of a mangrove A. marina were assessed for adenosine deaminase activity by plating method. Optimization of reaction process was carried out using response surface methodology of central composite design. The potent strain was identified based on 16S rRNA sequencing and phylogeny. Of five endophytic strains, EMLK1 showed a significant deaminase activity over other four strains. The conditions for maximum activity of the isolated adenosine deaminase are described. The potent strain EMLK1 was identified as Lysinibacillus sp. (JQ710723) being the first report as a mangrove endophyte. Mangrove-derived endophytic bacillus strain Lysinibacillus sp. EMLK1 is proved to be a promising source for the production of adenosine deaminase and this enzyme deserves further studies for purification and its application in disease diagnosis.

Characterization and expression analysis of three CBF/DREB1 transcriptional factor genes from mangrove Avicennia marina

Three CBF/DREB1 (C-repeat binding factor/dehydration responsive element-binding factor 1) homologues were isolated from mangrove Avicennia marina and designated AmCBF1, 2 and 3. Multiple sequence analysis showed that the three deduced proteins all contain an AP2 DNA-binding domain and two CBF signature sequences. According to the phylogenetic analysis, these proteins belong to the A-1 subgroup of the DREB subfamily. Expression analyses based on quantitative real-time PCR revealed that the AmCBF2 displayed relatively high expression under normal conditions, with the highest level in stems, while both AmCBF1 and 3 were weakly expressed without stress. The three genes also showed different responses to various environmental stimuli. The AmCBF2 was inducible by cold, drought, high salinity, heavy metals, as well as abscisic acid (ABA), and exhibited much stronger induction by cold, drought, Pb2+ or Zn2+ than by NaCl, ABA or Cd2+. In contrast, both AmCBF1 and AmCBF3 displayed insignificant changes under these stimuli. These results indicate that the three AmCBF genes play different roles in A. marina and the AmCBF2 might be involved in the signaling pathway of cold, drought and heavy metal stress response.

Water use patterns of estuarine vegetation in a tidal creek system

Water availability is a key determinant of the zonation patterns in estuarine vegetation, but water availability and the use of different water sources over space and time are not well understood. We have determined the seasonal water use patterns of riparian vegetation over an estuarine ecotone. Our aim was to investigate how the water use patterns of estuarine vegetation respond to variations in the availability of tidal creek water and rain-derived freshwater. The levels of natural stable isotopes of oxygen and hydrogen were assessed in the stem of the mangrove Avicennia marina (tall and scrub growth forms), Casuarina glauca and Melaleuca quinquenervia that were distributed along transects from river/creek-front towards inland habitats. The isotopic composition of plant tissues and the potential water sources were assessed in both the wet season, when freshwater from rainfall is present, and the dry season, when mangrove trees are expected to be more dependent on tidal water, and when Casuarina and Melaleuca are expected to be dependent on groundwater. Our results indicate that rainwater during the wet season contributes significantly to estuarine vegetation, even to creek-side mangroves which are inundated by tidal creek water daily, and that estuarine vegetation depends primarily on freshwater throughout the year. In contrast, high intertidal scrub mangroves were found to use the greatest proportion of tidal creek water, supplemented by groundwater in the dry season. Contrary to prediction, inland trees C. glauca and M. quinquenervia were found also to rely predominantly on rainwater--even in the dry season. The results of this study reveal a high level of complexity in vegetation water use in estuarine settings.

Effect of Trichoderma on soil phosphate solubilization and growth improvement of Avicennia marina

The present study assessed phosphate solubilization by the fungus Trichoderma as well as phytase enzyme activity and growth effects on seedlings of the mangrove Avicennia marina. Ten isolates of Trichoderma derived from the rhizosphere of A. marina were tested for their ability of in vitro phosphate solubilization using the NBRIP culture broth containing tricalcium phosphate (Ca3(PO4)2) as the insoluble phosphate. All the isolates were found to solubilize Ca3(PO4)2, with a maximum effect for the isolate TSK8 of soluble phosphate (301μgml−1), after 72h of incubation at 30°C. Extra-cellular phytase activity of the isolates appeared to be induced only in the presence of Ca3(PO4)2. This enzyme activity was maximal with the isolate TSK8 (318±2Uml−1 after 120h). The fungal treatments with TSK8 enhanced total mangrove seedlings biomass significantly (p<0.05) by 48%, 19% and 11% when supplemented respectively with soluble super phosphate (KH2PO4), without any phosphate and insoluble tricalcium phosphate (Ca3(PO4)2). The study revealed the phosphate solubilizing potential of Trichoderma, which has the potential to improve soil fertility and mangrove growth.

Inverse relationship between salinity and n-alkane δD values in the mangrove Avicennia marina

Hydrogen isotope ratios in lipids derived from mangroves have the potential to be used for paleohydrologic reconstructions and could serve as a much needed tool for establishing past climate variability in the tropics. We assessed the effect of salinity on the apparent fractionation factor, αa, between mangrove derived n-alkanes and their source water for Avicennia marina (gray mangrove) specimens collected along a 28PSU salinity gradient in the Brisbane River Estuary. Our results indicate that there is an inverse relationship between the apparent fractionation factor and salinity. This salinity effect is large enough to override variability in the isotopic composition of source water, which plays a dominant role in determining the hydrogen isotope ratio of leaf waxes in other vascular plants. We suggest that this relationship may be due to (i) increased discrimination against deuterium during water uptake at high salinity, (ii) increased production of compatible solutes from D enriched pyruvate at high salinity, resulting in more hydrogen from D depleted NADPH being incorporated in leaf waxes, and/or (iii) increased secretion of salty brine by leaves at high salinity, resulting in (iii.a) higher relative humidity at the leaf surface, and (iii.b) introducing the possibility that D depleted water of hydration is absorbed by the leaf. Our results indicate that hydrogen isotope ratios of mangrove lipid biomarkers can be developed as a paleosalinity indicator. They also imply that care must be taken when interpreting hydrogen isotopic variations in non-source specific higher plant lipids in sediments where both mangrove and non-mangrove plants contribute organic material.

Hyperspectral leaf signature as an added dimension for species discrimination: case study of four tropical mangroves

Hyperspectral leaf reflectance of a plant provides unique information that is characteristic of that plant. The present investigation is a preliminary attempt to assess whether spectra of leaves of mangrove species recorded under field conditions contain adequate spectral information for discerning mangroves at species rank. The paper highlights the hyperspectral characteristics of leaf surfaces of four prominent tropical mangrove species, viz., Avicennia alba, Avicennia marina, Rhizophora mucronata and Sonneratia caseolaris, found in the tidal forests of India. Hyperspectral observations were recorded using a field spectroradiometer, and pre-processed and averaged reflectance values of samples for three types of arrangements, viz., (1) randomly arranged leaves, (2) dorsal leaf surfaces and (3) ventral leaf surfaces of the species were statistically tested using one-way ANOVA to see whether the values significantly differed at every spectral location. All the four species were statistically different at all the spectral locations with majority of the bands exhibiting 99% confidence level. Finally, discriminant analysis was performed to identify the bands for maximum separability for the three types of arrangement of the leaves of the species taken separately and in different combinations. The optimal Wilks’ Lambda (L) were achieved with: six, three, eleven, six, five, thirteen and eleven wavelengths for discriminating random leaves of the four species, dorsal and ventral surfaces of A. alba, A. marina, R. mucronata, S. caseolaris, upper leaf surfaces of all the species, lower leaf surfaces, respectively. Factor analysis was used as an added tool to identify the wavelengths that were uncorrelated and contained maximum information in the combination of selected wavelengths. The results confirmed the unique spectral signatures of the four species, which could be explained in terms of leaf properties unique to the species. Cellular structure and pigmentation of the isolateral leaves of S. caseolaris are very different from the dorsiventral ones of the other three, which significantly changed the reflectance characteristics of the species.

Differential responses of the mangrove Avicennia marina to salinity and abscisic acid.

Salinisation of the soil can cause plant water deficits, ion and nutrient imbalances and toxic reactions. The halophyte, Avicennia marina (Forssk.) Vierh., is a mangrove that tolerates a wide range of soil salinities. In order to understand how salinity affects plant growth and functioning and how salinity responses are influenced by the water deficit signalling hormone abscisic acid (ABA) we grew A. marina seedlings under two non-growth limiting salinities: 60% seawater and 90% seawater and with and without exogenously supplied ABA. We measured growth, photosynthesis, sap flow, aquaporin gene expression, hydraulic anatomy and nutrient status as well as sap ABA concentrations. ABA addition resulted in a drought phenotype (reduced sap flow, transpiration rates and photosynthesis and increased water use efficiency and aquaporin expression). In contrast, growth in high salinity did not lead to responses that are typical for water deficits, but rather, could be characterised as drought avoidance strategies (no reduction in sap flow, transpiration rates and photosynthesis and reduced aquaporin expression). Tissue nutrient concentrations were higher in seedlings grown at high salinities. We did not find evidence for a role for ABA in the mangrove salinity response, suggesting ABA is not produced directly in response to high concentrations of NaCl ions.

PENGARUH KADAR ABU GOSOK SELAMA PEREBUSAN DAN LAMA PERENDAMAN AIR TERHADAP KADAR TANIN BUAH DAN TEPUNG MANGROVE (Avicennia marina)

Mangrove fruit has the potential to be developed as a potential food source, but the presence of toxins in the fruit are considered harmful if consumed in the long run. Therefore, research needs to be done to eliminate or reduce the levels of toxins in the mangrove fruit, The poison in one of which is the fruit of mangrove tannins. One alternative to reduce the levels of toxins in the fruit of the mangrove scrub with ash and water immersion. This research used Completely Randomized Design, factorial pattern consisting of two factors with three replications, factor I was rubbing ash powder content (5%, 10%, and 15%), and factor II is long soaking water for 6 hours (with 4, 8, 12 times the turnover of water). The results showed that treatment with boiling some rubbing ash content (5%, 10%, and 15%) and long soaking water to give a significant influence (P <0.05) toward decreased levels of mangrove Avicennia marina fruit tannins. Treatment of boiling ash content of 15% gave the lowest reduction is 28.92% and the long soaking water for 6 hours with a change of water 12 times giving the low tannin levels decrease is 28.80%, as well as mangrove fruit flouring will A.marina lower levels of tannin by 28.44%.

Effect of Marine Mangrove Avicennia marina (Forssk.) Vierh Against Acetic Acid−Induced Ulcerative Colitis in Experimental Mice

Ulcerative colitis and Crohn's disease are two conditions that have many features in common and are referred as inflammatory bowel disease (IBD). Patients with IBD are predisposed to colorectal cancer. This investigation evaluates the effect of marine mangrove Avicennia marina against acetic acid-induced colitis. The treatment of A marina extract significantly decreased the colonic lipid peroxides, glutathione peroxidase, and serum nitric oxide and significantly increased the colonic and erythrocyte superoxide dismutase and glutathione levels compared with colitis control. In addition, A marina extract significantly decreased the lesion score and wet colon weight compared with colitis control. Treatment with A marina extract reflects its therapeutic activity against UC by minimal damage of colonic epithelial cells compared with colitis control during histopathologic examination. These protective role of A marina extract against UC could be attributed to the presence of higher levels of decanoic acid, diethylhydroxylamine (DEHA), pentanoic acid, pyrrolidine, 4-chlorophenyl, thiazolidinones, and arabinopyranoside (flavonoid). These findings suggest that A marina extract could be useful as a potential (natural) therapeutic agent for IBD.

Salinity increases the triterpenoid content of a salt secretor and a non-salt secretor mangrove

The present study describes the effect of salinity on the triterpenoid content of the salt secretor mangrove Avicennia marina and the non-secretor Rhizophora stylosa. Mangrove seedlings were grown for eight months in 0%, 0.5%, 1.5%, 2.0% and 3.0% salt concentration. The growth of both species was increased by salt with maximal stimulation at 1.5%, and this elevation appeared to be attenuated by increasing the salt concentration above 1.5%. The triterpenoid compositions of three types of chemical structures, lupane (lupeol, lupenone), oleanane (β-amyrin, taraxerol, germanicol), and ursane (α-amyrin), were studied. In addition, the phytosterol components campesterol, stigmasterol and β-sitosterol were analyzed. The total triterpenoid contents in the roots and leaves of A. marina for the 0% group were 87.0 and 66.2 μg g −1, respectively, and increased significantly to 173.1 and 142.6 μg g −1 with 3% salinity. The higher salinity also significantly increased the total concentration of phytosterols in the leaves and roots of this species. A similar increase in the concentration of both triterpenoids and phytosterols was observed in the roots and leaves of R. stylosa with increasing salt concentration. Thus, the triterpenoid concentration was increased by salinity in the roots and leaves of both A. marina and R. stylosa irrespective of their differences in salt management by salt excretion or by a non-excretion mechanism. Comparison of the triterpenoid concentration in four species of growing mangrove seedlings revealed a correlation between the total triterpenoid content and the salt tolerance based on the habitat zonation on Iriomote Island. A. marina thrives closest to sea and had the highest content of triterpenoids (173.1 μg g −1 in 3% salt group). Therefore, it is likely that the triterpenoid content play an important role in mangrove plants for protection from salinity in both salt-secretors and non-secretors.

Has the Herbicide Diuron Caused Mangrove Dieback? A Re-Examination of the Evidence

ABSTRACT The claim that the herbicide Diuron in agricultural runoff caused dieback of the grey mangrove (Avicennia marina) in Central Queensland, Australia, has influenced government policies including programs to save the Great Barrier Reef. Several investigations on mangrove dieback in Central Queensland river estuaries have been published during the past decade. However, proof of a causal link between mangrove dieback and Diuron remains inconclusive. This study presents a systematic review of the evidence using Hill's Criteria of Causation. Our review shows that using concentrations of the chemical bound to sediment as a measure for biological availability in either glasshouse or field studies is inappropriate. The appropriate measure is Diuron concentration in solution and this parameter bears no simple relationship to concentration bound to sediment, and is not strongly correlated with mangrove health. Only when the herbicide is applied in experimental investigations at many orders of magnitude higher than measured in rivers has an impact on A. marina been demonstrated. Evidence from field studies suggests burial of pneumatophores, the plant's breathing roots, following flood events is a more likely causal factor in mangrove dieback, whereas any contribution from Diuron remains unproven.

Improved growth performance of the mangrove Avicennia marina seedlings using a 1-aminocyclopropane-1-carboxylic acid deaminase-producing isolate of Pseudoalteromonas maricaloris

Out of 62 bacterial isolates obtained from the mangrove Avicenniamarina rhizosphere that grows along the Abu Dhabi coast, United Arab Emirates (UAE), an isolate of Pseudoalteromonas maricaloris (Wild type strain) (WT) produced relatively high levels of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase in vitro. Application of this WT strain under greenhouse conditions to A. marina seedlings significantly (P < 0.05), reduced endogenous levels of ACC in the roots and shoots, and significantly (P < 0.05) increased the levels of in planta endogenous plant growth regulators (PGRs) including indole-3-acetic acid (IAA), indole-3-pyruvic acid (IPYA), putrescine (Put), spermidine (Spd) and spermine (Spm) in roots and shoots compared with control mangrove seedlings. WT application has also significantly (P < 0.05) increased photosynthetic pigment contents, photosynthetic carbon assimilation, plant water use efficiency and promoted mangrove seedlings growth characteristics including increased dry weight and length of roots and shoots, total leaf area and the number of the side branches compared with control mangrove seedlings. In comparison, an ACC deaminase non-producing mutant strain (NPM) failed to reduce endogenous levels of ACC in the roots and shoots and also failed to increase endogenous PGRs and photosynthetic pigments and did not promote seedling growth. Both WT and NPM strains were incapable of producing in vitro detectable levels of IAA, IPYA, Gibberellic acid (GA3), zeatin (Z), Put, Spd and Spm in the culture filtrates. This study demonstrated for the first time the ability of ACC deaminase-producing bacteria to promote mangrove growth under greenhouse conditions. P. maricaloris has potential as biological inoculants to promote the growth of mangrove seedlings in afforestation programs in nutrient impoverished sediments in hyper-saline coastal areas in the UAE.

Biosynthesis, Characterization and Biological Evalutation of Fe(III) and Cu(II) Complexes of Neoaspergillic Acid, a Hydroxamate Siderophore Produced by Co-cultures of two Marine-derived Mangrove Epiphytic Fungi

A hydroxamate siderophore, neoaspergillic acid (1), and a red pigment, ferrineoaspergillin (2) which is an Fe(III) complex of 1, were produced by co-cultures of two epiphytic fungi from a rotten fruit of the mangrove Avicennia marina from the South China Sea, and a new Cu(II) complex of 1, designated as cuprineoaspergillin (3), was also prepared by treatment of 1 with cupric acetate. All the compounds (1-3) were characterized by physical and chemical techniques, including 1H NMR, ESIMS, and photoelectron energy spectra. In the bioassays, compounds 1-3 showed significant inhibitory activities against selected Gram-positive and Gram-negative bacteria, and compound 1 also exhibited moderate inhibitory activities against human cancer cell lines SPC-A-1, BEL-7402, SGC-7901 and K562.

Hypersalinity effects on leaf ultrastructure and physiology in the mangrove Avicennia marina

The effects of hypersalinity on leaf ultrastructure and physiology in the mangrove, Avicennia marina, were investigated by comparing leaves of adult trees growing naturally in the field under seawater and hypersalinity conditions in Richards Bay, South Africa. We tested the hypothesis that hypersalinity has a deleterious effect on membranes and cellular organelles such as chloroplasts and mitochondria, which would impact negatively physiological processes, such as ion and water relations, and photosynthetic performance. Soil ψ and soil salinity were −2.96 ± 0.07 MPa and 35 ± 2.8 psu in the seawater salinity site, compared to −5.91 ± 0.42 MPa and 58 ± 3.6 psu respectively, in the hypersaline site. In the hypersaline site, leaves were smaller and thicker, with thicker cuticles, while chloroplasts, mitochondria and nuclei exhibited swelling and disintegration, compared to those at seawater salinity. Multivesicular structures and vesicles, observed in vacuoles, chloroplasts, mitochondria, and along cell walls and plasma membranes, were more abundant in leaves from the hypersaline than the seawater site, and were probably indicative of greater plant salt uptake in the former site. Leaf concentrations of total chlorophyll and chlorophylls a and b were lower in trees from the hypersaline site by 33%, 29%, and 45% respectively, compared to those at seawater salinity. Midday minimum xylem ψ was −3.82 ± 0.33 MPa in the seawater site and −6.47 ± 0.45 MPa in the hypersaline site. In the hypersaline site, the concentration of leaf Na + was 40% higher, while those of K +, Ca 2+, and Mg 2+ were lower by 45%, 44%, and 54% respectively, than those in the seawater site. CO 2 exchange and the intrinsic photochemical efficiency of PS II were significantly lower in trees from the hypersaline site by 48 and 19% respectively. The ultrastructural evidence supported the physiological data that A. marina trees in the hypersaline site are under extreme salinity stress and that this species is growing there at the upper limit of its salt tolerance.