Polymorphic microsatellites in a mangrove species,Rhizophora mangle L. (Rhizophoraceae)

Twenty‐six microsatellite loci were isolated and characterized from the mangrove species Rhizophora mangle using (GT)_n and (CT)_n repeats. Eighty‐four per cent of the clones contained microsatellite sequences; the most common dinucleotides were the (GA/CT) and (CA/GT) repeats. Ten primers were selected to investigate the polymorphism among individuals of R. mangle from two natural populations of the Colombian Pacific Coast. The observed heterozygosity per locus varied from 0.20 to 0.80, the power of discrimination was 0.32–0.84 and the power of exclusion was 0.03–0.75. This set of microsatellites offers an efficient tool for population genetics studies on this species.     

Sun-shade adaptability of the red mangrove,Rhizophora mangle (Rhizophoraceae): Changes through ontogeny at several levels of biological organization

Rhizophora mangle L., the predominant neotropical mangrove species, occupies a gradient from low intertidal swamp margins with high insolation, to shaded sites at highest high water. Across a light gradient, R. mangle shows properties of both “light-demanding” and “shade-tolerant” species, and defies designation according to existing successional paradigms for rain forest trees. The mode and magnitude of its adaptability to light also change through ontogeny as it grows into the canopy. We characterized and compared phenotypic flexibility of R. mangle seedlings, saplings, and tree modules across changing light environments, from the level of leaf anatomy and photosynthesis, through stem and whole-plant architecture. We also examined growth and mortality differences among sun and shade populations of seedlings over 3 yr. Sun and shade seedling populations diverged in terms of four of six leaf anatomy traits (relative thickness of tissue layers and stomatal density), as well as leaf size and shape, specific leaf area (SLA), leaf internode distances, disparity in blade–petiole angles, canopy spread: height ratios, standing leaf numbers, summer (July) photosynthetic light curve shapes, and growth rates. Saplings showed significant sun/shade differences in fewer characters: leaf thickness, SLA, leaf overlap, disparity in bladepetiole angles, standing leaf numbers, stem volume and branching angle (first-order branches only), and summer photosynthesis. In trees, leaf anatomy was insensitive to light environment, but leaf length, width, and SLA, disparities in bladepetiole angles, and summer maximal photosynthetic rates varied among sun and shade leaf populations. Seedling and sapling photosynthetic rates were significantly depressed in winter (December), while photosynthetic rates in tree leaves did not differ in winter and summer. Seasonal and ontogenetic changes in response to light environment are apparent at several levels of biological organization in R. mangle, within constraints of its architectural baiiplan. Such variation has implications for models of stand carbon gain, and suggest that response flexibility may change with plant age.     

Population genetic structure,introgression, and hybridization in the genus Rhizophora along the Brazilian coast

Mangrove plants comprise plants with similar ecological features that have enabled them to adapt to life between the sea and the land. Within a geographic region, different mangrove species share not only similar adaptations but also similar genetic structure patterns. Along the eastern coast of South America, there is a subdivision between the populations north and south of the continent's northeastern extremity. Here, we aimed to test for this north‐south genetic structure in Rhizophora mangle, a dominant mangrove plant in the Western Hemisphere. Additionally, we aimed to study the relationships between R. mangle, R. racemosa, and R. × harrisonii and to test for evidence of hybridization and introgression. Our results confirmed the north‐south genetic structure pattern in R. mangle and revealed a less abrupt genetic break in the northern population than those observed in Avicennia species, another dominant and widespread mangrove genus in the Western Hemisphere. These results are consistent with the role of oceanic currents influencing sea‐dispersed plants and differences between Avicennia and Rhizophora propagules in longevity and establishment time. We also observed that introgression and hybridization are relevant biological processes in the northeastern coast of South America and that they are likely asymmetric toward R. mangle, suggesting that adaptation might be a process maintaining this hybrid zone.     

Linking physiological processes with mangrove forest structure: phosphorus deficiency limits canopy development, hydraulic conductivity and photosynthetic carbon gain in dwarf Rhizophora mangle

Spatial gradients in mangrove tree height in barrier islands of Belize are associated with nutrient deficiency and sustained flooding in the absence of a salinity gradient. While nutrient deficiency is likely to affect many parameters, here we show that addition of phosphorus (P) to dwarf mangroves stimulated increases in diameters of xylem vessels, area of conductive xylem tissue and leaf area index (LAI) of the canopy. These changes in structure were consistent with related changes in function, as addition of P also increased hydraulic conductivity ( K _s), stomatal conductance and photosynthetic assimilation rates to the same levels measured in taller trees fringing the seaward margin of the mangrove. Increased xylem vessel size and corresponding enhancements in stem hydraulic conductivity in P fertilized dwarf trees came at the cost of enhanced midday loss of hydraulic conductivity and was associated with decreased assimilation rates in the afternoon. Analysis of trait plasticity identifies hydraulic properties of trees as more plastic than those of leaf structural and physiological characteristics, implying that hydraulic properties are key in controlling growth in mangroves. Alleviation of P deficiency, which released trees from hydraulic limitations, reduced the structural and functional distinctions between dwarf and taller fringing tree forms of Rhizophora mangle .     

Sterols and fatty acids from three species of mangrove

The hydrolysis of steryl esters on thin-layer chromatographic plates by porcine pancreatic lipase is described. The sterols and fatty acids produced were separated on the same plate, recovered, and analysed by gas-liquid chromatography for their compositions. Synthetic cholesteryl esters containing various saturated and unsaturated fatty acids and synthetic steryl oleates with various sterols were lipolysed along with steryl esters of Acanthus ilicifolius, Bruguiera gymnorhiza and Rhizophora mucronata mangrove leaves. The major sterol was sitosterol which was accompanied by cholesterol, campesterol, stigmasterol and 28-isofucosterol. In addition, stigmast-7-en-3β-ol was present in R. mucronata leaves. The component fatty acids found in all three species were 16:0, 18:0, 18:1, 18:2 and 18:3. The relative proportions of the sterols and fatty acids were significantly different from the chemotaxonomic standpoint. The results obtained by carrying out plate lipolysis for 45 min at 40° compared well with those produced by conventional chemical hydrolysis.     

Chloroplast microsatellite markers for the mangrove tree species Bruguiera gymnorrhiza, Kandelia candel, and Rhizophora stylosa, and cross-amplification in other mangrove species

Chloroplast microsatellite (cpSSR) markers were developed for three ecologically and economically important tree species in the mangrove family, Rhizophoraceae: Bruguiera gymnorrhiza, Kandelia candel, and Rhizophora stylosa. Noncoding regions of chloroplast DNA (cpDNA) from each species were separately amplified using universal chloroplast primers. Six, two, and three polymorphic cpSSR loci in B. gymnorrhiza, K. candel, and R. stylosa, respectively, were developed from amplified noncoding cpDNA regions. Characterization of 216, 156, and 253 individuals of B. gymnorrhiza, K. candel, and R. stylosa, respectively, collected from different natural mangrove populations (B. gymnorrhiza, 9; K. candel, 7; R. stylosa, 9) on Iriomote Island in Japan showed that these loci provide cpSSR markers with polymorphisms ranging from two to four alleles per locus and gene diversity between 0.027 and 0.480. These cpSSR markers will be useful for analyzing the maternal lineage distributions and population genetic structures of the three species. Several of these markers may also be useful in similar studies of other mangrove species.     

Primary Phloem Development in the Shoot Apex of Rhizophora mangle L. (Rhizophoraceae)

The primary phloem in the shoot apex of the mangrove Rhizophora mangle L. is largely confined to the comparatively condensed area between the first three leaf pairs. The main extension zone, surrounded by the stipular sheath of the third leaf pair, contains vascular bundles arranged in a procambial ring and characterized by a well-developed primary phloem and a less advanced xylem. The phloem consists of a great number of sieve elements, an equal number of associated companion cells, and a few phloem-parenchyma cells. The differentiation of the sieve-element protoplast (with e.g., chromatolytic nuclear degeneration, loss of the vacuole and most organelles) proceeds largely according to a well-known pattern. Their P-type plastids, however, form their protein crystals rather late and therefore cannot be used as an early cell marker. Lateral sieve-element walls are distinct from other wall parts and walls of other cells by their heavy nacreous thickenings, the formation of which is shown to be strictly correlated with the occurrence and orderly arrangement of cortical microtubules.     

Isolation and molecular characterization of genetically diverse antagonistic, diazotrophic red-pigmented vibrios from different mangrove rhizospheres

Genetic diversity of red-pigmented vibrios from different mangrove rhizospheres ( Porteresia coarctata, Avicennia marina and Rhizophora mucronata ) collected from Pichavaram mangrove, India was investigated. Twenty red–pink pigmented strains were isolated, 16S rRNA gene analyses indicted that these isolates belong to the genus Vibrio and were phylogenetically closely related to the type strains of Vibrio rhizosphaerae and Vibrio ruber . The rep-PCR analysis using GTG₅ and BOX primers had similar groupings, and segregated these pigmented Vibrio isolates including two type strains into seven unique genotypic groups (REP groups A1–A7). The rhizosphere of P. coarctata harbors highly genetically diverse groups of red-pigmented vibrios compared to other plants. Multilocus sequence analysis using four genetic loci ( pyrH, recA, rpoA , 16S rRNA) clearly supported the hypothesis that strains MSSRF38 (REP group A5) and MSSRF39 (REP group A6) could represent new Vibrio species. Biological functions of these vibrios were also determined and it was found that all these isolates have antagonistic activity against phytopathogens, and isolates belonging to REP groups A5 and A6 were positive for nifH gene by PCR. In conclusion, this study for the first time demonstrates the occurrence of genetically diverse groups of antagonistic, diazotrophic red-pigmented vibrios from different mangrove plants and suggests a new ecological role for vibrios as heterotrophic plant associated rhizobacteria.     

Isolation and characterization of eight compound microsatellite markers in a mangrove tree Kandelia candel (L.) Druce

Kandelia candel is an important mangrove tree species of family Rhizophoraceae. Here we isolated eight codominant compound microsatellite simple sequence repeat (SSR) loci from K. candel. Our isolated loci provided compound SSR markers with polymorphism of three to 11 alleles per locus. The expected and observed heterozygosities ranged from 0.230 to 0.887 and from 0.083 to 1.00, respectively. These markers would be the useful tools for analysing questions concerning population genetic structure and mating system of K. candel.     

Isolation and characterization of microsatellite loci in the red mangrove Rhizophora mangle (Rhizophoraceae) and its related species

Fourteen microsatellite markers were isolated from the red mangrove Rhizophora mangle (Rhizophoraceae), a widely distributed mangrove plant in the New World and West Africa. The range of expected heterozygosity of these markers was 0.000–0.672 in the two populations of R. mangle. Cross-species testing was examined for five other species of Rhizophora, and Kandelia candel and Bruguiera gymnorrhiza. All 14 markers could be amplified in R. samoensis, thirteen in R. racemosa, and six markers in all other species of Rhizophora. Our findings greatly increase the utility of these markers.     

Pentacyclic triterpenoids and sterols from seven species of mangrove

The isolation of pentacyclic triterpenoids from seven species of fresh mangrove leaves using a simple and rapid method is described. The leaves were homogenized using chloroform—methanol and the extract was diluted with water to precipitate out triterpenoids which were separated into neutral and acidic fractions. These were analysed by gas-liquid chromatography as acetyl and trimethylsilyl ether derivatives on a 3% OV-17 column. Sterols were isolated from the chloroform layer by preparative thin layer chromatography and were analysed by gas-liquid chromatography as their trimethylsilyl ether derivatives on a 3% OV-17 column. The triterpenoids found were α-amyrin, β-amyrin, lupeol, oleanolic acid and ursolic acid in most of the samples. Sterols found in all the samples were cholesterol, campesterol, stigmasterol, sitosterol and stigmast-7-en-3β-ol. Retention indices of the triterpenoids and sterols have been determined.     

Nomenclatural notes and typification of names in the mangrove tribe Rhizophoreae (Rhizophoraceae) of India

The nomenclatures of the taxa of the mangrove Rhizophoraceae of India have been scrutinized and 20 names are lectotypified or neotypified. In addition, the holotypes of some names are located for the first time with clarifications provided. Since natural hybridization is common in Rhizophoraceae, its consequences for the correct application of names is also briefly discussed.     

Development and characterization of ten new microsatellite markers in a mangrove tree species Bruguiera gymnorrhiza (L.)

Bruguiera gymnorrhiza is an ecologically and somewhat economically important mangrove tree species. We isolated 10 polymorphic microsatellite loci from B. gymnorrhiza using a dual‐suppression polymerase chain reaction (PCR) technique. These loci provided microsatellite markers with polymorphism of two to five alleles per locus within 216 individuals from nine natural populations of B. gymnorrhiza on Iriomote Island, the Sakishima Islands, Japan. The expected and observed heterozygosities ranged from 0.220 to 0.720 and from 0.104 to 0.447, respectively.     

Physiological responses of the mangrove Rhizophora mangle grown in the absence and presence of NaCl

Abstract. Propagules of the mangrove, Rhizophora mangle L., were precultivated for 9 months in a greenhouse. The young plants were transferred into unaerated nutrient solutions without and with 200 mol m ³ NaCl and subsequently their growth, their water relations and the photosynthetic properties of their leaves were studied. Growth of the salttreated plants was significantly increased, while the control plants gradually died off after finishing the experiments. The shoot water potential and the stomatal resistance of the leaves were lowered while the chlorophyll contents and the chlorophyll a/b ratio in the leaves of salt-treated plants were increased by NaCl, the net result being an enhanced rate of CO₂ assimilation. The leaves of both sets of plants showed diurnal fluctuations in malic acid concentration which were more pronounced in the leaves of salt treated plants which, additionally, were more succulent. However, the plants showed no net CO₂ fixation at night, indicating that Rhizophora mangle is a CAM-cycling plant. After 200 d of cultivation without or with NaCl, the Na⁺, Cl and K⁺ concentrations in tissues and vacuoles were measured. Energy-dispersive X-ray microprobe analyses on root vacuoles of control plants reveal Na⁺ preference, on those of salt treated plants a strong K⁺ preference. Vacuolar K⁺ concentrations are neither affected by NaCl nor do they vary across the root radius. High vacuolar Na⁺ and Cl concentrations are found in the hypodermis followed by a stepwise decrease towards the inner root cortex cells. Ion concentrations of the photosynthetically active leaf tissues seem to be regulated by (1) radial filtration across the root cortex: (2) ion exchange of the xlem parenchyma cells: and (3) sequestration of Na⁺ and Cl in the hypodermal water storage tissue of the leaves.     

Photosynthetic characteristics of dwarf and fringe Rhizophora mangle L. in a Belizean mangrove

Twin Cays (Belize) is a highly oligotrophic mangrove archipelago dominated by Rhizophora mangle L. Ocean‐fringing trees are 3–7 m tall with a leaf area index (LAI) of 2.3, whereas in the interior, dwarf zone, trees are 1.5 m or less, and the LAI is 0.7. P‐fertilization of dwarf trees dramatically increases growth. As a partial explanation of these characteristics, it was hypothesized that differences in stature and growth rates would reflect differences in leaf photosynthetic capacity, as determined by the photochemical and biochemical characteristics at the chloroplast level. Gas exchange and chlorophyll fluorescence were used to compare photosynthesis of dwarf, fringe and fertilized trees. Regardless of zonation or treatment, net CO₂ exchange (A) and photosynthetic electron transport were light saturated at less than 500 µmol photons m^?2 s^?1, and low‐light quantum efficiencies were typical for healthy C₃ plants. On the other hand, light‐saturated A was linearly related to stomatal conductance (g_s), with seasonal, zonal and treatment differences in photosynthesis corresponding linearly to differences in the mean g_s. Overall, photosynthetic capacity appeared to be co‐regulated with stomatal conductance, minimizing the variability of C_i at ambient CO₂ (and hence, C_i/C_a). Based on the results of in vitro assays, regulation of photosynthesis in R. mangle appeared to be accomplished, at least in part, by regulation of Rubisco activity.     

Two new alkaloids from Penicillium oxalicum EN-201, an endophytic fungus derived from the marine mangrove plant Rhizophora stylosa

Two new alkaloids including a new prenylated indole derivative possessing a piperidine moiety, penioxamide A (1), and a new decaturin analogue, 18-hydroxydecaturin B (2), were isolated and identified from Penicillium oxalicum EN-201, an endophytic fungus obtained from the inner tissue of the fresh leaves of marine mangrove plant Rhizophora stylosa. Their structures and absolute configurations were elucidated on the basis of the spectral data and CD analysis. Compound 1 bears the rare anti relative configuration in the bicyclo[2.2.2]diazaoctane ring, while compound 2 has a pyridinyl-α-pyrone substructure which is rare among natural products. Compounds 1 and 2 showed potent brine shrimp lethality with LD₅₀ values of 5.6 and 2.3 μM, respectively.     

Root biomechanics in Rhizophora mangle: anatomy,morphology and ecology of mangrove’s flying buttresses

Background and Aims Rhizophora species of mangroves have a conspicuous system of stilt-like roots (rhizophores) that grow from the main stem and resemble flying buttresses. As such, the development of rhizophores can be predicted to be important for the effective transmission of dynamic loads from the top of the tree to the ground, especially where the substrate is unstable, as is often the case in the habitats where Rhizophora species typically grow. This study tests the hypothesis that rhizophore architecture in R. mangle co-varies with their proximity to the main stem, and with stem size and crown position.Methods The allometry and wood mechanical properties of R. mangle (red mangrove) trees growing in a mangrove basin forest within a coastal lagoon in Mexico were compared with those of coexisting, non-buttressed mangrove trees of Avicennia germinans. The anatomy of rhizophores was related to mechanical stress due to crown orientation (static load) and to prevailing winds (dynamic load) at the study site.Key Results Rhizophores buttressed between 10 and 33 % of tree height. There were significant and direct scaling relationships between the number, height and length of rhizophores vs. basal area, tree height and crown area. Wood mechanical resistance was significantly higher in the buttressed R. mangle (modulus of elasticity, MOE = 18·1 ± 2 GPa) than in A. germinans (MOE = 12·1 ± 0·5 GPa). Slenderness ratios (total height/stem diameter) were higher in R. mangle, but there were no interspecies differences in critical buckling height. When in proximity to the main stem, rhizophores had a lower length/height ratio, higher eccentricity and higher xylem/bark and pith proportions. However, there were no directional trends with regard to prevailing winds or tree leaning.Conclusions In comparison with A. germinans, a tree species with wide girth and flare at the base, R. mangle supports a thinner stem of higher mechanical resistance that is stabilized by rhizophores resembling flying buttresses. This provides a unique strategy to increase tree slenderness and height in the typically unstable substrate on which the trees grow, at a site that is subject to frequent storms.     

Effect of environment and gibberellins on the early growth and development of the red mangrove, Rhizophora mangle L.

Seedlings of the red mangrove, Rhizophora mangle L., were subjected to a variety of salinity, light, and plant growth regulator treatments to examine the influence of these factors on early development. Stem, leaf, and root growth were significantly enhanced in both low salinity seawater and under reduced intensities of solar radiation. Semi-quantitative analyses of GAs by enzyme-linked immunoabsorbant assays (ELISA) suggest that under these conditions the early 3/13 hydroxylation GA₁ biosynthetic pathway is predominant in R. mangle. Concentrations of GA₁ and GA₁₉-like substances were highest in propagules exhibiting enhanced development. Attempts to identify the endogenous GAs by GC-MS were unsuccessful, most likely due to undetermined impurities present in mangroves. Exogenous applications of GA₃ to R. mangle were moderately successful in alleviating shoot growth inhibitions observed at higher salinities and light levels. The role of gibberellins is discussed in terms of metabolic responses to the external environment and possible impacts upon the distribution of this species.     

Elevated CO2 alters anatomy,physiology, growth,and reproduction of red mangrove (Rhizophora mangle L.)

Mangroves, woody halophytes restricted to protected tropical coasts, form some of the most productive ecosystems in the world, but their capacity to act as a carbon source or sink under climate change is unknown. Their ability to adjust growth or to function as potential carbon sinks under conditions of rising atmospheric CO₂ during global change may affect global carbon cycling, but as yet has not been investigated experimentally. Halophyte responses to CO₂ doubling may be constrained by the need to use carbon conservatively under water-limited conditions, but data are lacking to issue general predictions. We describe the growth, architecture, biomass allocation, anatomy, and photosynthetic physiology of the predominant neotropical mangrove tree, Rhizophora mangle L., grown solitarily in ambient (350 ll^–1) and double-ambient (700 ll^–1) CO₂ concentrations for over 1 year. Mangrove seedlings exhibited significantly increased biomass, total stem length, branching activity, and total leaf area in elevated CO₂. Enhanced total plant biomass under high CO₂ was associated with higher root:shoot ratios, relative growth rates, and net assimilation rates, but few allometric shifts were attributable to CO₂ treatment independent of plant size. Maximal photosynthetic rates were enhanced among high-CO₂ plants while stomatal conductances were lower, but the magnitude of the treatment difference declined over time, and high-CO₂ seedlings showed a lower P_max at 700 ll^–1 CO₂ than low-CO₂ plants transferred to 700 ll^–1 CO₂: possible evidence of downregulation. The relative thicknesses of leaf cell layers were not affected by treatment. Stomatal density decreased as epidermal cells enlarged in elevated CO₂. Foliar chlorophyll, nitrogen, and sodium concentrations were lower in high CO₂. Mangroves grown in high CO₂ were reproductive after only 1 year of growth (fully 2 years before they typically reproduce in the field), produced aerial roots, and showed extensive lignification of the main stem; hence, elevated CO₂ appeared to accelerate maturation as well as growth. Data from this long-term study suggest that certain mangrove growth characters will change flexibly as atmospheric CO₂ increases, and accord with responses previously shown in Rhizophora apiculata. Such results must be integrated with data from sea-level rise studies to yield predictions of mangrove performance under changing climate.