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ANGIOPTERIS a pteridophyte fern (king fern)

The document provides detailed information on the systematic position and morphology of the genus Angiopteris, a group of primitive ferns classified under the class Eusporangiate and order Marattiales. It describes the plant's external and internal structures, reproductive processes, and the unique features of its gametophyte and spore production, including its explosive spore dispersal mechanism. Additionally, Angiopteris evecta is noted for its antibacterial properties and is commonly cultivated as an ornamental plant.

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ANGIOPTERIS BY, G. STEPHY AROKIYA MARY 24PBO106
SYSTEMATIC POSITION KINGDOM - PLANTAE DIVISION - PTERIDOPHYTA SUB – DIVISION - PTEROPSIDA CLASS - EUSPORANGIATE ORDER - MARATTIALES FAMILY - ANGIOPTERIDACEAE GENUS - ANGIOPTERIS
INTRODUCTION • The class Eusporangiate is a small group of primitive ferns. • This class is represented by 17 Genera and 30 Species. The members of this class shows the following distinguishing features: • Sporangia are borne on the fertile spikes (Ophioglossum), or on the abaxial side of the lamina (Angiopteris, Marattia). • The Sporangium develops from a group of initial cells. • The Sporangial Jacket is more than one cell in thickness. • They produce only one type of spores, i.e., they are homosporous. • The class Eusporangiate has only two orders – Marattiales and Ophioglossales.
• The Order Marattiales includes those eusporangiate ferns which bear sporangia on the abaxial side of the lamina. • They mostly occur in the tropical rain forests. • There are seven living genera; of these Archangiopteris, Macroglossum, Protomarattia and Christensenia are very small. • Angiopteris, Marattia and Danaea are conspicuous because of their massive fleshy axis and large fronds. • The young leaves are circinate vernation (coiled) and each leaf has two stipules at it’s base. • The Sporangium opens by slits on either side or by a pore. • The gametophyte is large, thalloid and green.
ANGIOPTERIS • Angiopteris has some 100 species overall. • They are distributed in Japan, Tropical Australia, New Caledonia, Madagascar and Polynesia. • Angiopteris evecta occurs throughout India up to an elevation of 2,500 meters.
EXTERNAL MORPHOLOGY • The Plant Body is Sporophytic i.e., the plant body is differentiated into root, stem and leaves. • The stem is large, upright and 60cm or more in height. • Angiopteris is shielded by fleshy stipules. • The leaves are Spirally arranged and form a Crown at the apex of the stem. • They are Pinnately compound, often large, 2 – 6 meters long. • A conspicuous swelling, called Pulvinus, is present at the base of each pinna. • The venation is open, dichotomously branched and veins are sub – parallel.
• The Young leaves shows typical Circinate vernation. • Numerous Adventitious roots arises from the basal part of the stem. They are somewhat fleshy, branched and mycorrhizic. • These adventitious roots arise endogenously and are inserted below the leaves. • The young stem grows by means of a single narrow apical cell, which is replaced by group of initials at maturity.
INTERNAL STRUCTURE The Internal structure of the Angiopteris consists of the following, They are: • Stem • Root • Pinna
ANATOMY OF THE STEM • The anatomy of the stem is complex and it varies with the age of the plant. • The Parenchymatous cortex has numerous mucilagenous ducts. • The fleshy nature of the stem is due to the absence of thick walled cells. • Mechanical support to the stem is provided by thick leaf bases. • The young stem is Protostelic. The stele is surrounded by a distinct layer of endodermis. • As the stem grows older, the stele becomes amphiphloic siphonostele with distinct leaf gaps.
ANATOMY OF ROOT • The internal structure of root is relatively simple. • The epidermal cells of the root forms the root hairs. • Some root hairs are multicellular. • There is a large parenchymatous cortex with many mucilagenous canals. • The Stele is surrounded by a single layer of endodermis and one or two layers of pericycle. • The Stele is Polyarch with 4 – 10 (or more ) long and thin xylem arms. • A small parenchymatous pith is present in the centre of the stele.
ANATOMY OF PINNA • The internal structure of a pinna is similar to that of the dicotyledonous leaf. • Both, the lower and the upper epidermis are single layered. • Stomata are confined to the lower epidermis. • The mesophyll is differentiated into 1 – 2 layers of elongated palisade like cells, followed by spongy parenchyma.
SPORE PRODUCING ORGANS • The sporangia forms linear, oblong or boat shaped sori on the lower surface of the pinnae near the margin. • Each Sorus has 8 – 14 or more sporangia which develops over a veinlet. • Few multicellular hairs are present along the margin of the sorus. • In Angiopteris, the entire sorus arises as a surface receptacular meristem. • All surface cells divide periclinally and then group of hypodermal cells differentiate as the Sporangial initials. • Each group of Sporangial initial forms a sorus.
• The mature Sporangium is large, massive and sessile. • The wall of sporangium is several layered : The outermost layer has stomata and the innermost layer has the Sporogenous tissue, which forms the Tapetum. • An arch of slightly thick walled cells, the annulus, is differentiated in the sporangial wall. • It extends vertically from one end to the other across the top of the sporangium. • Contractions in the cells of the annulus results in the splitting of sporangium along the line of the dehiscence. • The spore output per sporangium is very large (1400 – 7500) in comparison to the leptosporangiate ferns.
GAMETOPHYTE • Germination of spores takes place within a few days after their shedding. • The spores forms large, perennial prothalli. • The Prothallus is dark – green, mycorrhizic and thalloid, resembling very much with thallose liverworts. • It contains a many celled thick central cushion and thin lateral wing – like extensions. • The growth of the central mycorrhizal cushion continues for quite a long time.
SEX ORGANS • The gametophyte is monoecious. • Archegonia initiates on the margins of the central cushion. • Eventually, the archegonia takes positions well within the cushion due to continuous growth of the plant. • Antheridia are formed on the wing – like extensions of the prothallus and they are more or less scattered. The sex organs present are as follows, • Antheridium • Archegonium
I. ANTHERIDIUM • The mature antheridium is massive and sunken in the tissue of the gametophyte. • It is surrounded by a single layered antheridial jacket. • It produces a large number of coiled multiflagellate antherozoids and opens at the surface of the prothallus through a triangular opercular cell.
II. ARCHEGONIUM • The archegonium consists of a 3 – 4 cells long neck and a venter. • The neck canal is occupied by a single binucleate neck canal cell and in the venter a venter canal cell and a large egg is present. • As the archegonium matures, it undergoes considerable stretching due to the growth of the cushion.
EMBRYO • Zygote is formed by the fusion of egg and antherozoid. • It enlarges and then divides transversely establishing an epibasal and a hypobasal cell. • The epibasal cell, lying close to the neck of the archegonium, forms a short single celled suspensor. • The hypobasal cell, called the embryonic cell, divides to form a small spherical mass of cells. • The polarity of the embryo becomes apparent at the quadrant or octant stage.
• The cells close to the suspensor (i.e., those towards the neck of the archegonium) form foot and the inner cells form stem, root and the first leaf. • Thus the development of the embryo in Angiopteris is endoscopic.
CONCLUSION • Angiopteris have antibacterial and antifungal properties in them. • These are invasive species. • Angiopteris is unique among the ferns in having explosively dispersed spores, which are thought to be caused by airspace between the spore layers. • These species have the unique spore dispersal mechanism in them. • Angiopteris evecta is often cultivated as an ornamental plant in gardens, parks and botanical gardens.
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