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Questions and Answers
What is the dominant and independent phase of the Riccia life cycle?
What is the dominant and independent phase of the Riccia life cycle?
Gametophyte
Riccia is a type of moss.
Riccia is a type of moss.
False
How is the Riccia thallus attached to the substratum?
How is the Riccia thallus attached to the substratum?
Root-like rhizoids
What type of cells make up the lower storage region of the Riccia thallus?
What type of cells make up the lower storage region of the Riccia thallus?
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Riccia is heterothallic, meaning it has separate male and female plants.
Riccia is heterothallic, meaning it has separate male and female plants.
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Where are the gametangia of Riccia embedded?
Where are the gametangia of Riccia embedded?
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What is the structure that encloses the egg cell in a Riccia archegonium?
What is the structure that encloses the egg cell in a Riccia archegonium?
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The Riccia sporophyte is made up of a foot, seta, and capsule.
The Riccia sporophyte is made up of a foot, seta, and capsule.
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What is the name of the protective layer that covers the Riccia capsule?
What is the name of the protective layer that covers the Riccia capsule?
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Riccia spores are diploid.
Riccia spores are diploid.
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What does the term 'chemotaxis' refer to in the context of Riccia reproduction?
What does the term 'chemotaxis' refer to in the context of Riccia reproduction?
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What is the first cell of the sporophytic generation in Riccia?
What is the first cell of the sporophytic generation in Riccia?
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What are the two layers of the spore wall in Riccia?
What are the two layers of the spore wall in Riccia?
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What does a Riccia spore germinate to produce?
What does a Riccia spore germinate to produce?
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Study Notes
Riccia Morphology and Reproduction
- Riccia is a bryophyte, with a dominant and independent haploid gametophyte phase.
- The gametophyte forms a dorsiventrally flat thallus, shaped as circular patches or rosettes on moist substrates.
- The thallus is dichotomously branched, with a dorsal groove or midrib.
- A growing point is located at the tip, and the thallus attaches to the substrate via rhizoids.
- Rhizoids are unicellular, smooth-walled, or tuberculate, aiding in anchorage and absorption.
- Multicellular, violet, obliquely placed scales retain moisture on the thallus.
Thallus Structure and Function
- The thallus displays a distinct upper photosynthetic region and a lower storage region.
- Photosynthetic filaments composed of chlorenchyma cells are arranged in parallel rows within the photosynthetic region, with air canals in between.
- Terminal cells of these filaments are globular and hyaline/transparent, forming a discontinuous upper epidermis.
- The lower storage region consists of parenchymatous cells that store food material.
- Sex organs (gametangia) are embedded within the storage region.
Sexual Reproduction
- Riccia is homothallic, meaning both male and female gametangia develop within the same thallus.
- Gametangia are embedded in the storage region.
- Male gametangia (antheridia): Located just below the dorsal groove, each antheridium comprises a stalk and a globular body. The body is encased by a sterile jacket that contains motile antherozoids or male gametes.
- Female gametangia (archegonia): Also located just below the dorsal groove, each archegonium is flask-shaped, with a venter enclosing an egg. A neck region with neck canal cells surrounds the venter.
Sporophyte Development
- After fertilization of the egg by an antherozoid, a diploid zygote forms, initiating the sporophytic generation.
- The sporophyte is exceptionally simple, consisting only of a capsule.
- The capsule is enclosed by a protective calyptra, developed from the venter of the archegonium.
- A sterile jacket encloses diploid sporocytes, which undergo meiosis, generating haploid spores.
- The calyptra disintegrates, releasing the spores.
- Each spore is triangular, unicellular, and uninucleate, with an outer spiny exosporium and an inner smooth endosporium.
- Mature spores germinate to produce a new haploid gametophyte.
- Foot and seta are absent in the sporophyte of Riccia.
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Description
Explore the fascinating morphology and reproduction of Riccia, a type of bryophyte. This quiz will cover the unique features of Riccia's gametophyte phase, thallus structure, and the roles of rhizoids and scales. Test your knowledge on how these characteristics enable Riccia to thrive in moist environments.
