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  Pteridophytes, Biology tutorial

Introduction to Pteridophytes:

Pteridophtyes are phylum of plants and vascular plants containing xylem and phloem tissues which reproduce by discharging spores rather than seeds, and they comprise highly diverse true ferns and other graceful, mainly forest-dwelling plants. There are approx eleven thousand various species of pteridophytes, making them most diverse land plants after flowering plants (angiosperms). Pteridophytes symbolize closest living relatives (sister group) to seed plants. Seed plants comprise angiosperms, conifers, and smaller assortment of other plants.

General Characteristics of Pteridophytes:

i. Pteridophytes include two distinct stages in life cycle. These are Gametophyte and Sporophytes that follow each other in regular succession. The 2 generations look different.

ii. Sporophyte is leading generation, independent of gametophyte; it has the vascular system and it is in different habitat.

iii. Pteridophytes show the great variation in form, size and structure.

iv. Many are herbaceous except the few woody tree ferns.

v. They may be dorsi-ventral or radial in symmetry.

vi. They include dichotomously or laterally branched stems which bear megaphyllous leaves.

vii. Roots are usually adventitious, main embryonic root being short-lived.

viii. Spores are made in special structures known as sporangia which are invariably subtended by life-like appendages called as sporophylls.

ix. In most cases, sporangia are compacted to form diverse spore producing regions known as strobile. Sporangia in some cases may be made inside specialized structures known as sporocarp.

x. Laves of the fern plant is known as frond.

Relationship of Pteridophytes with Other Groups:

Pteridophytes and Bryophytes:

Resemblances:

1. Liverworts and Pteridophytes illustrate likeness in vegetative structure of gametophytes.

2. The female and male reproductive structures are archegonium and antheridium, respectively.

3. Opening of mature sexual reproductive organs and following fertilizations are situation by presence of water in liquid salt that is both need water for fertilization.

4. They generally illustrate the distinct and clearly distinct heteromorphic alternative of generations and two generations follow each other in normal succession.

5. Spores arise in same manner in both groups.

6. Growth of embryo happens in archegonium.

7. Young sporophyte or embryo is partly parasitic upon gametophyte.

Dissimilarity:

1. In Pteridophytes, sporophyte is independent at maturity and is dominant stage of life cycle instead of gametophyte as in bryophytes.

2. Sporophyte include true roots, stems, and leaves and well grown conducting tissues-xylem and phloem, that are absent in bryophytes.

3. Some of Pteridophyte is heterosporous but all bryophytes are homosporous.

Pteridophytes and Flowering Plants:

In Pteridophytes, plant body is not separated in root and shoots system, in flowering plants, plant body distinguished in distinct root and shoot system. Vascular bundles are less grown in Pteridophytes, (tracheids) Flowering plants has well grown vascular bundles (xylem and phloem). There is no pollen grain, pollen tube; in Pteridophytes following plant includes pollen grain. Pteridophytes include no seeds white flowering plants make seeds with cotyledons or endosperms.

Morphology of a Pteridophyte-Pteris vittata:

Pteris is the extensively distributed genus with approx 250 species. It develops plentifully in cool, damp and shady places in tropical and subtropical regions of world. Pteris Vittata is a low level fern that brings out new leaves all through the year. It is extremely common along mountain walls and develops up to 1200 metres above sea level.

All species of pteris are terrestrial, perennial herbs having either creeping or semi erect rhizome covered by scales. Roots begin either from lower surface or all over surface of rhizome. Leaves are compound in most species, but some have simple leaves like Pteris cretica. Stalk of leaf continues as rachis and bears leaflets known as pinnae. In Pteris vittata, pinnae present near base are tips are smaller than those in middle.

Condition for Adaptation:

Sporophyte illustrates greater degree of difficulty in structural organization. It is prearranged into stem, root and leaves. Vascular tissues (xylem and Phloem) are grown only in sporophyte. Aerial parts are covered with the layer of cuticle. On Epidermis, there are stomata for exchange of gases. The anatomical complexities of sporophyte of Pteridophytes assisted in inhabiting the much wider range of environmental state than gametophyte could do.

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