Psilopsida:
Psilopsida is a class of vascular plants that includes the whisk ferns, a group of primitive plants that are among the oldest living vascular plants on Earth. It includes both living and non-living genera.
• Occurrence:
They are commonly found in tropical and subtropical regions of the world, and they are particularly abundant in moist, shady habitats such as rainforests including both eastern and Western hemispheres.
• Structure of Plant body:
The body of Psilopsida, also known as whisk ferns, has a simple but unique structure that is quite different from other vascular plants. They lack true roots, leaves, and flowers, and their stems are photosynthetic and flattened, resembling small green ribbons or straps.
The stem of Psilopsida is the primary organ of the plant and is in particular unbranched, however it may divide dichotomously to provide same branches. The stems can develop as much as a meter in length and are commonly green in coloration, because of the presence of chloroplasts that allow them to perform photosynthesis. Along the stem, there are scale-like outgrowths called enations and absence vascular bundles. The stem is hooked up to ground thru rhizomes, which can be horizontal stems that develop underground and bring a community of roots. The rhizomes of whisk ferns are usually thick and fleshy, and they could save water and nutrients for the plant.
Life Cycle──Reproduction
Psilopsida reproduces both sexually and asexually, and it exhibits a unique pattern of reproduction known as alternation of generations.
The alternation of generations in Psilopsida involves two distinct generations:
the gametophyte and the sporophyte.
Gametophyte Generation:
The gametophyte is a small, independent plant that produces gametes through mitosis. The gametes, which are haploid, unite to form a diploid zygote, which grows into the sporophyte generation through sexual reproduction.
Sexual reproduction:
Sexualal reproduction in Psilopsida occurs through the production of spores. The sporangia, which are structures located at the base of the enations, produce spores through meiosis.
These spores are dispersed and can grow into new gametophytes, completing the alternation of generations cycle.
We can say that the alternation of generations in Psilopsida allows for both sexual and asexual reproduction, providing the plant with a range of options for producing new individuals.
This strategy has allowed Psilopsida to adapt to a wide variety of environments and continue to thrive in many ecosystems.
Sporophyte Generation:
The sporophyte is the larger, more prominent plant that produces spores through meiosis. These spores are haploid and can grow into new gametophytes, completing the cycle.
Asexual Reproduction:
Asexual reproduction in psilopsida occurs through various methods including fragmentation, apophysis, and spore formation.
In general, sporophyte generation is domaint common and in Psilopsida.
The spores are produced the terminal portion thick walled portions called sporangia.These may either present on singly on at the tips of erect branches or in the group s of three's(synangia) at the base of stem.
These plants are homosporous.
Classification:
Psilopsida is a class of primitive vascular plants that are among the oldest living vascular plants on Earth.
• Class:
The division is Classified into two classes:Plsilophytopsida that includes extinct genera and psilopsida that includes living genera Psilotum and Tmeispteris.
• Order:
They are classified into a single order, Psilotales, which includes two families, Psilotaceae and Tmesipteridaceae.
• Family:
The family Psilotaceae includes two genera, Psilotum and Tmesipteris, and consists of around 12 species. Psilotum, also known as whisk ferns, is the more widespread of the two genera and is found in tropical and subtropical regions worldwide. Tmesipteris is a small genus that is found in Australia, New Zealand, and the Pacific islands.
The family Tmesipteridaceae includes a single genus, Tmesipteris, and consists of around 20 species. Tmesipteris is found in Australia, New Zealand, and the Pacific islands, and it is similar in appearance to Psilotum.
• Psilotum:
The Psilotum is the first living genera in Psilopsida.
Psilotum, also known as whisk ferns, is a genus of primitive vascular plants belonging to the family Psilotaceae. It is a unique plant that lacks true roots, leaves, and flowers, and instead has dichotomously branched stems that resemble small green ribbons or straps.
Psilotum is found in tropical and subtropical regions worldwide, and is typically found in moist, shady habitats such as forests, swamps, and stream banks. The stems of Psilotum are photosynthetic, meaning they are able to perform photosynthesis and produce their own food.
• Vegetative Morphology:
The plant is sporophyte. As a plant, it lacks genuine leaves, roots, and plant life, but instead has dichotomously branched stems which can be photosynthetic.
The vegetative morphology of Psilotum is characterised with the aid of its stem structure. The stems are aerial and dichotomously branched, which means that they break up into identical branches at every branching point. The branches are easy and unbranched, with no leaves or lateral appendages. Instead, the branches have tiny, scale-like enations that characteristic in photosynthesis.
The stems of Psilotum are also characterised by means of the presence of 3 awesome regions: the rhizome, the aerial stem, and the enations. The rhizome is the underground part of the stem, and it is chargeable for anchoring the plant and absorbing water and nutrients from the soil.
The aerial stem grows above ground, and it is answerable for photosynthesis and the manufacturing of spores. The enations are small, scale-like systems that develop alongside the aerial stem and are liable for photosynthesis.
Despite its loss of actual leaves and roots, Psilotum continues to be capable of perform photosynthesis and convey its very own meals. Its specific stem structure and enations have allowed it to evolve to numerous environments, and it maintains to thrive in tropical and subtropical regions global.
• Internal Anatomy:
Psilotum is a genus of primitive vascular plants that have a unique anatomical structure. The anatomy of Psilotum is characterized by its three distinct meristem layers and its stem structure.
The three meristem layers in Psilotum are the protoderm, ground meristem, and procambium.
• The protoderm gives rise to the epidermis, which covers the surface of the stem and is responsible for protection and water loss regulation.
• The ground meristem gives rise to the cortex, which is the region between the epidermis and the vascular tissue. The cortex provides mechanical support and is also involved in storage and transport of nutrients.
• The procambium gives rise to the vascular tissue, which includes the xylem and phloem. The xylem is responsible for water transport, while the phloem is responsible for the transport of organic compounds.
• The stem anatomy of Psilotum is also unique. The stem is aerial and dichotomously branched, with no leaves or lateral appendages.
• The outermost layer of the stem is the epidermis, which is a single layer of cells that cover the surface of the stem.
• Beneath the epidermis is the cortex, which is made up of several layers of parenchyma cells.
• The cortex provides mechanical support and is involved in storage and transport of nutrients.The vascular tissue of the stem consists of two types of cells, xylem and phloem, which are arranged in bundles.
• The xylem is located towards the center of the stem and is responsible for water transport.
• The phloem is located towards the outside of the stem and is responsible for the transport of organic compounds.
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| Internal Structure of Aeial stem and Rhizome |
• Rhizome:
Psilotum also has an underground stem called the rhizome. The rhizome is similar in structure to the aerial stem, but it's miles modified for anchoring the plant and absorbing water and vitamins from the soil. The rhizome also has a layer of cells referred to as the endodermis, which surrounds the vascular tissue and is responsible for regulating the motion of water and nutrients among the cortex and the vascular tissue.
Frequently Asked Questions-FAQs
• How do Plsilopsida reproduce?
Their members showcase alternation of generations.They reproduce asexually by using spore formation in sporangia at the tip in their branches. They can also reproduce sexually by gametes formation through antheridia and archegonia.
• Why Psilotum is called whisk fern?
Psilotum is called whisk fern due to the fact its stem is thin and lengthy like a whisk, and it lacks leaves, branches, and roots like a fern. In past,it changed into alsed used as a small broom, made by using tying a handful of its branches together.
• Why Psilotum is called living fossil?
Psilotum is considered a living fossil due to the fact it is one of the oldest lineages of vascular plants that still exist today, dating back to the devonian duration over four hundred million years in the past. It has remained surprisingly unchanged in its basic morphology, and its evolutionary records presents crucial insights into the early evolution of land flora.
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