Division Tracheophyte
Tracheophytes are called vascular plants because of the existence of vascular tissues i.e., xylem and phloem.
These are the successful groups of land plants. They have the ability to adjust the rough land habitat most effectively and amongst them, the flowering plants today have a controlled land environment.
The development of the following complicated vegetative and reproductive qualities enabled the vascular plants in general and flowering plants specifically to become the primary flora of land:
- They have roots, stems, and leaves.
- They have vascular systems in stems, roots, and leaves.
- Tracheophytes have protected sporangia, resulting in the development of the seed.
- They develop a pollen tube. So, they do not need water for the transmission of male gametes to female gametes.
- They develop flowers and fruits.
- They show heteromorphic alternation of generation.
Natural History:
First Tracheophytes appear in the fossil record by 408 MYA. The vascular system enables plants to grow much bigger and taller than those without. Over time competitors cause the refinement of the vascular system. At some point in between 390MYA and 354MYA wood, true leaves, and advanced rooting systems were all developed.
At that time some vascular plants became able to grow to 35 meters tall. The very first Tracheophytes were all Pteridophytes (spore-making vascular plants). While the vascular system was becoming more advanced so was the reproductive system. Eventually resulting in the advancement of the spermatophytes (seed-bearing vascular plants).
Sub-division of Tracheophytes
The Tracheophytes are further sub-divided into four sub-divisions, Psilopsida, Lycopsida, Sphenopsida, and Prteropsida.
Psilopsida (Psilophyta)
In Psilopsida, plants have rootless sporophytes. The stem is differentiated into an underground root and an aerial part. Both are dichotomously branched. The root bears rhizoids, both carry out the function of the root. The aerial branches are green, leafless and bear small veinless outgrowths, and perform photosynthesis. The reproductive organs of sporophyte are sporangia which develop at the tips of long or short branches, or on lateral sides of branches. The internal structure of the stem is simple. Vascular tissue is narrow, central, and solid without pith, with a broad cortex.
Psilopsida is considered to be the earliest group of vascular plants. The majority of the representatives of this group have actually ended up being extinct, for example, Horneophyton, Psilophyton, Cooksonia, and so on.
- There are only 2 living genera Psilotum, and Tmesipeteris.
The gametophyte is thalloid. It is colorless and underground. Its cells consist of a fungus which supplies food to the gametophyte and in return gets protection from it. Such beneficial cooperative relationship among the two members (fungus and plant) is stated to be symbiosis; or mycorrhizal association.
Lycopsida
The plants of Lycopsida have sporophytes differentiated into roots, stem, and true leaves. The leaves are small and single- veined, they are likewise called microphylls. The plan of leaves is spiral or opposite. The sporangia establish singly on the upper side of the sporophylls, which might or might not be set up to form strobili. The sporophyte might have sporangia of one kind as in Lycopodium or of two kinds i.e., microsporangia and megasporangia as in Selaginella.
Lycopsids are likewise called club mosses/spike mosses because of their club/spike-shaped strobili and small leaves resembling mosses. On the basis of types of spores produced in the sporophyte, they are therefore referred to as being ‘homosporous’ or ‘heterosporous’ respectively.
This condition is called homospory and heterospory. Selaginella resembles seed-producing plants (spermatophytes) because of its heterosporic condition and some other characters. The gametophyte of Lycopsida is mainly underground.
Sphenopsida
In Sphenopsida (Horsetails), the sporophyte is differentiated into root, stem, and leaves. The leaves may be broadened or scale-like and are constantly arranged in whorls. Plants coming from this group are also called arthrophytes because the whole plant body is made up of a large number of joints.
The main stem is not smooth, it has a great number of ridges and furrows. Each node has a whorl of branches. The sporangia are born upon structures called sporangiophores, aggregated to form strobili. Each sporangiophore has a slender stalk and an expanded disc at its complimentary end. The sporangia appear on the underside of the disc. The thalloid gametophytes grow upon clayey soil and on mud, e.g., Equisetum.
Pteropsida
Pteropsida is divided into 3 classes (i) class Filicineae (ii) class Gymnospermae (iii) class Angiospermae. The class Filicineae consists of seedless plants with foliar sporangia (sporangia attached to fronds). The leaves are called fronds. When the frond is immature and young, it is coiled, this pattern of development is called circinate vernation. It is an important character of this group.
Multiple-Choice Questions (MCQs) with Answers
- Division Tracheophyte:
- What characterizes tracheophytes?
- a) Lack of vascular tissues
- b) Presence of xylem and phloem
- c) Absence of root, stem, and leaves
- d) Limited adaptation to land habitat
Answer: b) Presence of xylem and phloem
- What is the significance of vascular tissues in tracheophytes?
- a) Restriction of growth
- b) Adaptation to aquatic habitats
- c) Limited height
- d) Enabling larger and taller growth
Answer: d) Enabling larger and taller growth
- When did the first tracheophytes appear in the fossil record?
- a) 200 MYA
- b) 354 MYA
- c) 408 MYA
- d) 500 MYA
Answer: c) 408 MYA
- What is a significant development in the reproductive system of tracheophytes?
- a) Development of fronds
- b) Evolution of sporangiophores
- c) Heteromorphic alternation of generation
- d) Circinate vernation
Answer: c) Heteromorphic alternation of generation
- Which sub-division of tracheophytes includes the earliest group of vascular plants?
- a) Psilopsida
- b) Lycopsida
- c) Sphenopsida
- d) Pteropsida
Answer: a) Psilopsida
- Psilopsida (Psilophyta):
- What is the primary distinguishing feature of Psilopsida?
- a) Presence of true leaves
- b) Dichotomous branching of stem
- c) Heterosporic condition
- d) Thalloid gametophyte
Answer: b) Dichotomous branching of stem
- Which of the following is a living genus in Psilopsida?
- a) Horneophyton
- b) Psilotum
- c) Cooksonia
- d) Psilophyton
Answer: b) Psilotum
- What type of gametophyte is characteristic of Psilopsida?
- a) Thalloid and green
- b) Filamentous and colorful
- c) Colorless and underground
- d) Leafy and photosynthetic
Answer: c) Colorless and underground
- Lycopsida:
- What are the leaves called in Lycopsida?
- a) Megaphylls
- b) Microphylls
- c) Fronds
- d) Sporophylls
Answer: b) Microphylls
- What term describes the arrangement of leaves in Lycopsida?
- a) Spiral or opposite
- b) Whorled
- c) Circinate vernation
- d) Heterospory
Answer: a) Spiral or opposite
- Which condition is observed in Selaginella, making it similar to seed-producing plants?
- a) Homospory
- b) Heterosporic
- c) Homosporic
- d) Heterosporous
Answer: b) Heterosporic
- Sphenopsida:
- Why are plants in Sphenopsida called arthrophytes?
- a) Due to jointed stems
- b) Presence of broad leaves
- c) Homosporous reproduction
- d) Filamentous gametophytes
Answer: a) Due to jointed stems
- Where do thalloid gametophytes of Sphenopsida grow?
- a) Sandy soil
- b) Clayey soil and mud
- c) Rocky surfaces
- d) Aerial environments
Answer: b) Clayey soil and mud
- Pteropsida:
- Which class in Pteropsida includes seedless plants with foliar sporangia?
- a) Gymnospermae
- b) Angiospermae
- c) Filicineae
- d) Lycopsida
Answer: c) Filicineae
- What is circinate vernation in Pteropsida?
- a) Jointed stem
- b) Spiral arrangement of leaves
- c) Coiled pattern of frond development
- d) Broad leaves in whorls
Answer: c) Coiled pattern of frond development
- Division Tracheophyte:
- What term is used to describe the vascular tissues present in tracheophytes?
- a) Cuticle
- b) Cortex
- c) Xylem and phloem
- d) Parenchyma
Answer: c) Xylem and phloem
- Which characteristic distinguishes tracheophytes as a successful group of land plants?
- a) Lack of reproductive structures
- b) Adaptation to aquatic environments
- c) Presence of vascular tissues
- d) Homosporous reproduction
Answer: c) Presence of vascular tissues
- Psilopsida (Psilophyta):
- What is the primary reproductive organ in Psilopsida?
- a) Sporophyll
- b) Sporangium
- c) Frond
- d) Rhizoid
Answer: b) Sporangium
- Lycopsida:
- Which term describes the club/spike-shaped strobili in Lycopsida?
- a) Heterospory
- b) Circinate vernation
- c) Microphylls
- d) Homosporous
Answer: b) Circinate vernation
- What type of leaves are characteristic of Lycopsida?
- a) Megaphylls
- b) Fronds
- c) Microphylls
- d) Sporophylls
Answer: c) Microphylls
- Sphenopsida:
- What is the main stem of Sphenopsida characterized by?
- a) Smooth texture
- b) Ridges and furrows
- c) Hairy surface
- d) Spiral arrangement
Answer: b) Ridges and furrows
- Pteropsida:
- Which class in Pteropsida includes plants with seeds enclosed in a fruit?
- a) Gymnospermae
- b) Filicineae
- c) Angiospermae
- d) Psilopsida
Answer: c) Angiospermae
- What is a characteristic feature of gametophytes in Pteropsida?
- a) Thalloid and green
- b) Underground and colorless
- c) Filamentous and photosynthetic
- d) Leafy and heterosporic
Answer: b) Underground and colorless
FAQs – Division Tracheophyte
- What are tracheophytes, and why are they called vascular plants?
- Tracheophytes are vascular plants characterized by the presence of vascular tissues, namely xylem and phloem. They are called vascular plants due to their well-developed vascular systems that facilitate the transport of water, nutrients, and sugars.
- What are the key features that enabled vascular plants to become the primary flora of land?
- Vascular plants, including flowering plants, possess roots, stems, and leaves. They have vascular systems in all these organs, protected sporangia leading to seed development, the ability to develop a pollen tube (eliminating the need for water in gamete transfer), the formation of flowers and fruits, and exhibit heteromorphic alternation of generation.
- When do the first tracheophytes appear in the fossil record, and what evolutionary developments do they exhibit?
- The first tracheophytes appear around 408 million years ago. Evolutionary developments include the refinement of the vascular system, the emergence of wood, true leaves, and advanced rooting systems, ultimately leading to the evolution of spermatophytes (seed-bearing vascular plants).
- What are the sub-divisions of tracheophytes, and what are their characteristics?
- Tracheophytes are subdivided into Psilopsida, Lycopsida, Sphenopsida, and Pteropsida. Each sub-division has unique characteristics, such as rootless sporophytes and simple internal structures in Psilopsida, differentiated sporophytes with microphylls in Lycopsida, whorled leaves in Sphenopsida, and various classes including seedless plants in Pteropsida.
- Tell us about Psilopsida (Psilophyta) and its significance in plant evolution.
- Psilopsida is considered the earliest group of vascular plants. It features rootless sporophytes with dichotomously branched stems, green aerial branches for photosynthesis, and simple internal stem structures. Despite the majority being extinct, living genera like Psilotum and Tmesipeteris showcase thalloid, underground gametophytes in a symbiotic relationship with fungi.
- What characterizes Lycopsida, and what distinguishes it from other divisions?
- Lycopsida, also known as club mosses, has sporophytes with roots, stems, and small, single-veined leaves (microphylls). The arrangement of leaves can be spiral or opposite. Lycopsids are unique for their club-shaped strobili and can be homosporous or heterosporous, with examples like Lycopodium and Selaginella.
- Describe the features of Sphenopsida (Horsetails) and their habitat preferences.
- Sphenopsida features sporophytes with roots, stems, and leaves arranged in whorls. The main stem has ridges and furrows, and sporangia develop on structures called sporangiophores, forming strobili. Thalloid gametophytes grow on clayey soil and mud, exemplified by plants like Equisetum.
- What are the classes within Pteropsida, and what is unique about each class?
- Pteropsida is divided into three classes: Filicineae, Gymnospermae, and Angiospermae. Filicineae includes seedless plants with foliar sporangia, exhibiting circinate vernation in young fronds. Gymnospermae and Angiospermae include seed-producing plants, with gymnosperms bearing naked seeds, and angiosperms having seeds enclosed in fruits.
Summary: Division Tracheophyte Tutorial
The Division Tracheophyte tutorial provides an in-depth exploration of vascular plants, showcasing their pivotal role in adapting to terrestrial environments. Here are the key takeaways:
- Vascular Adaptations:
- Tracheophytes, or vascular plants, derive their name from the presence of vascular tissues (xylem and phloem). This adaptation allows them to thrive in diverse land habitats, with flowering plants exhibiting remarkable control over their surroundings.
- Evolutionary Milestones:
- The tutorial traces the evolution of vascular plants, emphasizing their development of roots, stems, leaves, and a sophisticated vascular system. The emergence of protected sporangia leading to seed formation, the evolution of pollen tubes for non-aquatic gamete transfer, and the development of flowers and fruits mark significant milestones.
- Natural History:
- The fossil record indicates the appearance of the first Tracheophytes around 408 million years ago. Evolutionary competition drove the refinement of the vascular system, with wood, true leaves, and advanced rooting systems evolving between 390 and 354 million years ago. This period witnessed the rise of tall vascular plants, with the initial Tracheophytes primarily being Pteridophytes.
- Sub-divisions:
- Tracheophytes are categorized into four sub-divisions: Psilopsida, Lycopsida, Sphenopsida, and Pteropsida. Each sub-division exhibits distinct characteristics and plays a unique role in the diversity of vascular plants.
- Psilopsida (Psilophyta):
- Psilopsida, considered the earliest group of vascular plants, features rootless sporophytes with dichotomously branched stems. Noteworthy extinct representatives include Horneophyton, Psilophyton, and Cooksonia. The living genera Psilotum and Tmesipeteris showcase thalloid gametophytes in a symbiotic relationship with fungi.
- Lycopsida:
- Lycopsida, or club mosses, possess sporophytes with differentiated roots, stems, and true leaves (microphylls). They exhibit homosporous or heterosporous conditions and are characterized by their club-shaped strobili. The gametophyte of Lycopsida primarily resides underground.
- Sphenopsida:
- Sphenopsida, known as horsetails, display sporophytes with differentiated roots, stems, and leaves arranged in whorls. The main stem features ridges and furrows, with sporangia developing on structures called sporangiophores. Thalloid gametophytes of Sphenopsida grow in clayey soil and mud.
- Pteropsida:
- Pteropsida is divided into three classes: Filicineae, Gymnospermae, and Angiospermae. Filicineae includes seedless plants with foliar sporangia, showcasing circinate vernation in young fronds. Gymnospermae and Angiospermae encompass seed-producing plants, with gymnosperms having naked seeds and angiosperms with seeds enclosed in fruits.
This tutorial illuminates the diverse and fascinating world of Tracheophytes, highlighting their adaptability and evolutionary significance in shaping the plant kingdom.