Dear friends, followers and members of the Steem platform, in this delivery I will share organographic and histological elements, as well as the bioindicator potential shown by the halophilic macrophyte Acrostichum aureum (PTERIDACEAE).
Acrostichum aureum, is not a true aquatic macrophyte, however, it can be placed in this category, since it lives in aquatic ecosystems, in similar conditions to macrophytes, such as; flood-tolerant herring root system, adaptability to grow on wet substrates, ability to extract mineral elements in fresh water and salt.
These conditions of similarity have allowed the Acrostichum aureum to be designated as a macrophyte, even though it is really a halophyte-type fern, hence the reason for categorizing it as a halophyte aquatic macrophyte.
However, there are characteristics and behaviors of Acrostichum aureum, such as its ability to thrive in saline water and acid pH, which turn this fern into a species Bio-indicator, which is why the objective of this post, is to describe the potential for extraction of soluble salts, in addition to its organographic and histological characterization.
In African countries, it is designated as a leather fern, in Florida the United States Golden leather fern , in Mexico and Venezuela it is called a beach fern or swamp fern.
Origin and distribution
The species Acrostichum aureum, originating in tropical mangroves of Africa and Asia, this fern has a geographical profile Pantropical , is widely distributed in the Caribbean and South America, specifically in regions that exhibit mangroves, marshes and salt marshes.
Genus Acrostichum in Venezuela
The genus Acrostichum, has four species, two are found in the neo-tropical biogeographic zone, among these; A. Aureum and A. danaeifolium., in relation to Venezuela A. danaeifolium, grows more in humid soils and coastal areas of the eastern states, while A. Aureum, is much more common to find, in aquatic ecosystems brackish mangroves, swamps and marshes, located in the western region and plains of the country 
Bio-indicator for saline and acid soils
The marsh fern, as it is known in the agro-livestock producing areas of the South of Lake Maracaibo - Venezuela, is an aquatic macrophyte of halophyte type, this indicates us, that it proliferates in flooded soils rich in organic matter, with high salinity and acid pH  .
The appearance of Acrostichum aureum, in humid zones dedicated to the agricultural and cattle activity, is an indicator of soils with loss of fertility, by the presence of high values of salts, that impede the normal growth and development of the crops, besides hindering the gain of biomass in species poaceae, used for the animal feeding.
Now, this halophyte condition of Acrostichum aureum, makes it the main aquatic macrophyte, regulator and extractor of salts dissolved in mangroves, swamps and marshes, which have high salinity values in their waters, acting as a desalination macrophyte.
Fig. 2 Acrostichum aureum plants. Author: @lupafilotaxia.
Way of life
The Acrostichum aureum, is an aquatic macrophyte of the group of emerging rooted, halophytic ecosystems, ie, that prospers phenologically in waters with high concentrations saline.
Fig.3, 4 and 5 On the right Acrostichum aureum seedlings, upper left side, Frondas pinnas can be seen, lower side adventitious roots. Author: @lupafilotaxia.
It exhibits roots of homogeneous morphology, of adventitious origin with appearance in knots and base of leaves.
It presents stems, with horizontal distribution exclusively rhizomatic, subterranean and of indefinite growth.
Acrostichum aureum, has organographically a dual physiological structure, called Fronda, which allows it to carry out photosynthesis and reproduction  .
A. Foliar morphology: The photosynthetic laminar structure of Acrostichum aureum, is constituted by; petiole, lamina composed of pinnate morphology, thick, slightly lignified (coriaceous), green-yellow color in the basal region and golden in the apical zone, wavy margins, apex accumulated and can measure approximately between 1 m long and about 50 cm wide.
B. Reproductive morphology: The region of the back of the frontier represents the fertile and reproductive structure of Acrostichum aureum, specifically in the apical area, where sporangia emerge.
Fig. 6 – 7 On the right, there is an apical zone of Fronde de Acrostichum aureum, on the left, there is a description of the reproductive back. Author: @lupafilotaxia.
The reproduction of Acrostichum aureum occurs in a similar way to the rest of the Pteridophytes, with the difference that the meristem segment generating the sporangia is located on the abaxial face (back side) of the follicles or reproductive pins exclusively apical, where they consecutively produce the germination of spores, giving rise to new individuals .
In addition to the reproduction and propagation by spores, this marsh fern can also multiply vegetatively, through the emission of individuals in the nodes of the rhizomatic stem.
The aquatic macrophyte halophyte Acrostichum aureum, sees favored its growth and development to full solar exposure, being able to reach the fronds the 3 meters of height, when they receive photons of light without arboreal intersection, reason why it is common to find it, in aquatic ecosystems with absence of trees, it is estimated that the fronds emit approximately 30 leaflets or pinnas, with petioles of 1 meter long.
The life cycle of Acrostichum aureum, is perennial, clearly differentiated in two stages, the first conspicuous sporophyte, followed by an unsuspecting gametophyte.
Habitat and invasive condition
The swamp fern grows in pantropical habitats, generally in areas with low water levels and on the shores of mangroves, swamps and swamps, Acrostichum aureum, has been catalogued as an invasive aquatic macrophyte, interfering with and displacing native tree flora.
Tolerance to salinity
The condition of aquatic halophyte macrophyte of Acrostichum aureum, allows it to register a favorable growth in waters with wide ranges of salinity , this salty tolerance, from the biological point of view has a positive influence on its mechanisms of reproductive and vegetative development.
Fig. 8 Acrostichum aureum, aquatic macrophyte halophyte type. Author: @lupafilotaxia.
Histology and organography
To carry out the microscopic study, fronds, petioles, rhizomes and roots of Acrostichum aureum were collected from the "Miguel Sarcos" Swamp, a swampy area located outside Santa Barbara de Zulia, Venezuela.
Fig. 9 Microscopic histological characterization of Acrostichum aureum. Author: @lupafilotaxia.
Materials and reagents used
- Plants of Acrostichum aureum (Marsh fern)
- Carrier sheets and coverslips
- Botanical dissection team
- Petri dishes
- Optical microscope
- Distilled water
Characterization and histological identification
Histological preparations were made by transverse, longitudinal and tangential slices, obtaining epidermal, parenchymal, cholenchymal, xylematic and floematic sections, which were later visualized with the optical microscope at 10x, identifying the differentiation and cellular morphology of each of the organographic structures evaluated.
The fronds of Acrostichum aureum, presents very cutinized epidermal cells, with sinuous walls, of elongated morphology.
Fig. 10 On the right side, the cross section of Fronde Acrostichum aureum is detailed, on the left side, the location of the cutinized and elongated epidermis is indicated. Author: @lupafilotaxia.
Regarding the stomas, they were only found on the obverse side, which indicates that Acrostichum aureum, presents Hypoestomatic type stomas, while the organization of the cells of the stomatic apparatus, could be visualized in Anomocytic distribution, that is to say, with more than three annexed or accompanying cells surrounding the occlusive cells in no apparent order.
Fig. 11 Anomocytic stomas Acrostichum aureum are observed on the right side, the shape of the stomatic appliance is indicated on the left side. Author: @lupafilotaxia.
Parenchymal and mechanical characterization
The middle lamina of the Acrostichum aureum fronds present a bifacial condition, with hypodermic cells observed on the upper segment, followed by mechanical tissue (visibly collagenous), well ordered and elongated parenchyma palisade, followed by spongy parenchyma cells with perceptible intercellular spaces.
Characterization of the petiole
The microscopic segment of the petiole of Acrostichum aureum, allowed to find morphological differences with respect to the fronds, when appreciating epidermal cells of hexagonal geometry and dispersed vascular bundles.
Fig. 12 On the left side, there is a detailed cross-section of the petiole Acrostichum aureum, on the right side, hexagonal epidermis and vascular bundle. Author: @lupafilotaxia.
Xylematic and phloematic characterization
In the root section of Acrostichum aureum, it was possible to detail sclerenchematic cortex with appreciable arenchematic chambers, followed by a stele around the medullary zone, inside which are constituted of central xylematic cells and phloematic tissue in exarca disposition, that is to say of centripetal tendency.
Fig. 13 On the left side, the adventitious root cross-section of Acrostichum aureum is detailed, on the right side, the following tissues are identified in order: epidermis, sclerenchematic cortex, medulla, vascular bundle (xylem - phloem), herringbone chambers. Author: @lupafilotaxia.
SCIENTIFIC CONTRIBUTIONS OF THIS PUBLICATION
- The article about Acrostichum aureum, contributes in the spreading of elements, such as; Potentiality Bio-indicator of salinity and acidity in agricultural zones and livestock with problems of fertility of soils product of long periods of flood, besides its salty indicator condition, it indicates the capacity of this species as desalination plant of aquatic ecosystems, finally, the organographic and histological characteristics, allow to elucidate the morphological differentiation of A. aureum, with respect to the true aquatic macrophytes.
BIBLIOGRAPHICAL REFERENCES CONSULTED AND CITED:
 Adams D, Tomlinson P. Acrostichum in Florida. American Fern Journal. 1979; 69 (2): 42-46.
 Eakle T. Photoperiodic control of spore germination of Acrostichum aureum. American Fern Journal. 1975; 65: 94-95.
 Li X., and Ong B. Responses of the photosynthesis to NaCl in gametophytes of Acrostichum aureum. Physiologia Plantarum. 1998; 102: 119-127.
 Lloyd R., and Buckley D. Effects of salinity on gametophyte growth of Acrostichum aureum and A. danaeifolium. Fern Gazette. 1986; 13:97–102.
 Sculthorpe C. The Biology of Aquatic Vascular Plants. 610 S. London: Edward Arnold Ltd. 1967.
 Vareschi V. Helechos. Flora de Venezuela, Instituto Botánico. Edición especial. Caracas. 1969; 1 (1).
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