PTERIDOPHYTA

Pteridophyta:

Introduction:

·         Pteridophytes made from greek word where pteros means winged; phyta means plant.

·         Haeckel (1866) called these groups of plants as pteridophytes because of their pinnate or feather               like fronds (leaves).

·         Pteridophytes are considered as first true land plant that evolved after bryophytes. Hence they are             sometimes called amphibians of plant kingdom  because like bryophytes they depend on an                       external source of water after fertilization.

·         Ferns are quite successful plants. They grow as perennial herbs, trees, epiphytes and floating                     plants.

·         They have exploited almost all terrestrial and fresh water units and dominate in some of them.

·         Ferns are megaphyllous plants whose leaves or fronds usually emerge by circinate venation. The               leaves are compound and are among the most complex leaves in the kingdom of green plants.

·         Pteridophytes are the most primitive seedless vascular plants that reproduce by means of spores.                Hence they are known as vascular cryptogams.

 

Salient Features:

Ø  They are vascular plants that reproduce and disperse via spores. These plants produce neither flowers nor seeds.

Ø  They are the first true land plants.

Ø  They are seedless vascular cryptogams.

Ø  Life cycle is heterologous diplohaplontic type.

Ø  Spoophyte has true stem, roots and leaves.

Ø  Spores develop in sporangia are homosporous or heterosporous.

Ø  Sporangia are produced in groups on sporophylls.

Ø  Young leaves of sporophyte show circinate venation.

Ø  Sex organs are multicellular and jacketed.

Distinguishing Features:

Ø  When the vascular plants successfully rooted themselves into the early earth’s soil 400 million years ago, they looked a little like pteridophytes.

Ø  Vascular plants are plants that have food transporting phloem and water transporting xylem tissues. Most pteridophytes have vascular tissue in their stem and roots.

Ø  Pteridophytes are seedless plants i.e. they have to pass on their genes to the next generation without using cones, fruits or any other forms of seed. Instead of seeds, ferns capsule or sporangia on the undersides of their green leaves or on specialized, non- green leaves called sporophyte.

Ø  Some pteridophytes are further united by the presence of single leaf per vein, an arrangement called as microphyll. Clubmosses, quilllworts and spikemosses have this simple leaf arranged.

Ø  True ferns, horsetails and whisk ferns all share larger more complex branching leaves known as megaphylls. Ferns and their kin share this megasporophyll trait with other modern vascular plants such as cone-bearing plants and flowering plants.

Classification of Pteridophytes:

                   I.  According to Arthur J. Eames (1936) classified into four groups on the basis of nature                              and relation of leaf and stem vascular anatomy and position of sporangia. Pteridophytes are                        classified into following classes:

1)      Psilopsida:

·         These are the oldest known vascular plant. Most of them have become extinct, only two living                    species.

·         Plant body is very simple and does not show much differentiation.

·         Dichotomously branched rhizome takes the place of roots.

·         Stem or axis is aerial, but either naked or have small spirally arranged leaves.

·         Sporangia are directly borne on the stem either terminal or lateral.

2)      Lycopsida:

·         Plant body is more advanced and shows differentiation into root, stem and leaves.

·         Leaves are microphyllous (small) having a single unbranched vein in the midrib region.

·         Sporangia are borne in the axil of the fertile leaves (sporophylls).

·         Sporophyll form compact strobili.

·         Examples are lycopodium, Selaginella.

3)      Sphenopsida:

·         Plant body still more advanced and shows differentiation into nodes and internodes like higher                 vascular plants.

·         Leaves are microphyllous arise in whorls at each node.

·         Sporangia develop on sporangiophores which form compact ones at the apex of fertile branches.                (Equisetum)

4)      Pteropsida:

·         Plant body shows much advancement towards higher vascular plants and is well differentiated into           root, stem and leaves.

·         Leaves also show great advancement and are megaphyllous (large) and pinnately compound.

·         Sporangia develop on the ventral surface of the sporophylls and usually aggregated into sori.

·         Example includes dryopteris, pteris, pteridium, polypodium.

 

II.  This classification was proposed by smith (1955), bold (1957) and zimmerman (1959).           Pteridophytes are classified in the following classes:

A.      Psilophyta:

·         They are the most primitive rootless plants with rhizoids.

·         They are dichotomously branched photosynthetic stem.

·         Leaves are often absent.

·         Protostele is there.

·         They are Homoporous.

·         Example is Psilotum.

B.      Lycophyta:

·         Lycophyta has differentiated plant body.

·         They have microphyllous leaves.

·         Protostele sometimes sphinostele.

·         Sporophylls aggregated to form strobili or cones.

·         They are homosporous or heterosporous.

·         Example includes selaginella, lycopodium.

C.      Sphenophyta:

·         All are fossils except equisetum.

·         They have differentiated plant body.

·         Stems are joined with nodes and internodes.

·         Scaly leaves are seen as whorl around the node.

·         Sporangia forming strobili or cones.

·         They are homosporous.

·         Example is equisetum.

D.      Pterophyta:

·         They are the most widely distributed vascular cryptogams.

·         Their plant body is differentiated.

·         Stems are mostly rhizomatous.

·         Leaves have macrophyllous structure called as fronds.

·         Young leaves show circinate venation or spirally coiled.

·         Stele is protostele, sphinostele or dictyostele.

·         Sporangia form sori on abaxial side of the leaf

·         Indusium may be true or false.

·         Homosporous or heterosporous.

·         Example includes pteris, marselia.

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Articles

ALGAE

Algae are eukaryotic organisms which are not differentiated into roots, stem and leaves. Algae are thalloid organism which are included in kingdom Plantae. Algae are classified into six classes.

GYMNOSPERM

Gymnosperms are small group of plants which act as connecting link between pteridophytes and angiosperm. Gymnosperms are classified into four classes;Cycadophyta, ginkophyta, gnetophyta, coniferophyta.

ANGIOSPERM

Angiosperms are the largest group of plant on this earth. They grow as trees, shrubs , bushes, herbs and small flower plants. Angiosperms are classified in two classes; Monocot and Dicot.

Contact

Feel Free To Email Us .At: