Saturday, May 18, 2024
General Agriculture

Characteristics and Classifications of Pteridophytes

Pteridophyte is the dominant phase, it possesses a vascular system and is differentiated into true root, stem, and leaves. Pteridophytes exhibit a great variation in form, size, and structure.

Most of the pteridophytes are herbaceous except for a few woody tree ferns. They may be dorsiventral or radial in symmetry and have dichotomously or laterally branched stems that bear microphyllous or megaphyllous leaves

The organization of the vascular cylinder (also called stele, see box item) in the sporophyte varies from simple primitive type to more complex forms. Besides, vessels are also present in some members.

The roots are generally adventitious, the primary embryonic root being short-lived. The spores are produced in special structures called sporangia that are invariably subtended by leaf-like appendages known as sporophylls.

The sporangia may be scattered throughout the vegetative axis or may be restricted to a particular area. They are in many cases compacted to form distinct spore producing regions called the cones or the strobill (sing, strobulus).

The sporangia in some cases may be produced within specialized structures called the sporocarp. Distinct segregation of vegetative and reproductive shoots and leaves has also been observed in some other species.

Have you ever noticed brown-black dots on the underside of a fern leaf? Each dot is a reproductive structure called sorus (plura, sori). It is a cluster of sporangia that contains spores.

Pteridophytes, in general, are homosporous i.e. they produce only one type of spores. However, a few species are heterosporous i.e. they produce two types of spores, microspores, and megaspores. A spore on germination produces gametophyte.

Heterosporous species produce micro-gametophytes as well as megagametophytes.

In general, pteridophytes form green, dorsiventrally differentiated, thallose gametophytes with sex organs restricted to the ventral surface. The sex organs may be embedded or projecting. They resemble those of bryophytes in general plan.

The female reproductive structure is archegonium and the male reproductive structure is an antheridium. The archegonium has invariably four longitudinal rows of neck cells whose height varies in different genera.

The antheridium consists of a single layer of sterile jacket of cells enclosing a mass of androcytes or antherozoid mother cells. Each androcyte gives rise to a single ciliated, motile antherozoid.

The opening of the mature sex organs and the subsequent fertilization is still conditioned by the presence of water. Hence like bryophytes, they could also be called amphibians of plant kingdom.

Now that you have studied the life cycle and the general characteristics of pteridophytes, can you compare them with bryophytes?

Bryophytes resemble pteridophytes in the following features:

Thallose liverworts and pteridophyte show similarity in vegetative structure of gametophytes.

Their female and male reproductive structures are archegonium and antheridium, respectively.

The opening of the mature sexual reproductive organs and the subsequent fertilization are conditioned by the presence of water in liquid state, i.e., both require water for fertilization.

They usually show a distinct and clearly defined heteromorphic alternation of generations and the two generations follow each other in regular succession.

Read Also: Life Cycle and Morphology of Some Pteridophytes

The spores arise in the same manner in both the groups. The spore mother cells are produced by the last division of the sporogenous tissues. Each of the spore mother cells undergoes meiotic division resulting in a tetrads of spores.

Development of embryo occurs in the archegonium

The young sporophyte or embryo is partially parasitic upon the gametophyte.

Now try to list the characteristics which distinguish pteridophyte from bryophytes

1. ………………………………………………….

2. ………………………………………………..

3. …………………………………………………

Compare your points with the following:

Characteristics and Classifications of Pteridophytes

Unlike bryophytes, in which sporophyte is dependent upon gametophyte physically and physiologically, the sporophyte is independent at maturity in pteridophytes, and is the dominant phase of life cycle instead of gametophyte.

In pteridophytes the sporophyte has true roots, stem, and leaves and well-developed conducting tissues – xylem and phloem, which are absent in bryophytes.

Some of the pteridophytes are heterosporous but all the bryophytes are homosporous.

As mentioned earlier, pteridophytes form an important link between bryophytes and seed plants. This suggests that they also resemble in some respects with spermatophytes.

Pteridophytes resemble seed plants in the following respects:

The sporophytes is dominant, typically photosynthentic phase of life cycle.

It is organized into stem, root and leaves.

The roots and the leafy shoots are provided with a conducting system made of specialized cells.

Some pteridophytes do approach seed-habit and some fossil pteridophytes had seed-like structures.

Due to their affinities with bryophytes as well as with higher vascular, plants, pteridophytes are also known as “Vascular Cryptogams” (non-seed producing plants).

Characteristics and Classifications of Pteridophytes

Characteristics and Classifications of Pteridophytes

Let us discuss the characteristics and classifications of Pteridophytes in details below;

Pteridophytes, a diverse group of vascular plants that includes ferns and their allies, exhibit a fascinating array of characteristics and classifications that set them apart in the botanical realm. Let’s delve into the unique features and classifications of these ancient green wonders.

Characteristics of Pteridophytes

1. Vascular Tissues: Pteridophytes boast well-developed vascular tissues, comprising xylem and phloem, allowing for the efficient transport of water, nutrients, and sugars. This vascular system enables these plants to grow taller and more structurally complex than non-vascular plants.

2. Alternation of Generations: The life cycle of pteridophytes is characterized by alternation of generations, where two distinct phases, the gametophyte, and the sporophyte, take turns in the reproductive process. This intricate dance between generations contributes to the adaptability and resilience of pteridophytes.

3. Fronds and Leaves: Pteridophytes are renowned for their unique leaves called fronds. These fronds often exhibit intricate patterns, providing an aesthetic appeal. The leaves play a crucial role in photosynthesis, contributing to the plant’s energy production.

4. Sporangia and Spores: Reproductive structures called sporangia are found on the undersides of fronds. These tiny capsules house spores, which are essential for the dispersal and propagation of pteridophytes. The spores are released into the environment, where they germinate and initiate the gametophyte phase.

5. Rhizomes and Roots: Pteridophytes typically grow from underground rhizomes, horizontal stems that give rise to roots and aerial shoots. This growth pattern aids in the spread and colonization of suitable habitats.

Read Also: Morphology, Life Cycle, and Classification of Bryophytes

Classifications of Pteridophytes

1. Ferns (Class Polypodiopsida): The largest group within Pteridophyta, ferns are characterized by well-defined leaves called fronds and are distributed worldwide. Examples include the sword fern (Nephrolepis exaltata) and the royal fern (Osmunda regalis).

2. Horsetails (Class Equisetopsida): Recognizable by their jointed stems and unique cone-like structures, horsetails, or Equisetums, are a distinct group of pteridophytes. They have a high silica content, making them historically valuable for scouring and polishing.

3. Clubmosses (Class Lycopodiopsida): Lycopods, commonly referred to as clubmosses, are primitive pteridophytes that often resemble mosses but are evolutionarily distinct. Their small, needle-like leaves cover upright stems, and they played a significant role in ancient ecosystems.

4. Whisk Ferns (Class Psilotopsida): Whisk ferns, represented by genera like Psilotum, are unique among pteridophytes due to their apparent lack of true roots. They have simple, dichotomously branching stems and are considered more primitive compared to other groups.

Read Also: Comprehensive Seed Farm Guide For Farmers

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Benadine Nonye is an agricultural consultant and a writer with over 12 years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education - PhD Student in Agricultural Economics and Environmental Policy... Visit My Websites On: 1. Agric4Profits.com - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. WealthinWastes.com - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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