Hornworts Overview and Structure
29 Questions
6 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of cyanobacteria Nostoc found in hornworts?

  • Producing oil bodies
  • Absorbing water
  • Fixing nitrogen (correct)
  • Photosynthesis

    • Hornworts have air chambers instead of mucilage.

    False

    What structure in hornworts is responsible for the production of spores?

    Sporangium

    Hornwort gametophytes can be identified by having _____ large chloroplast in each cell.

    <p>one</p> Signup and view all the answers

    Match the following characteristics with their corresponding terms related to hornworts:

    <p>Mucilage = Replaces air chambers Pseudoelaters = Helps spread spores Columella = Tissue column on the capsule Near-basal meristem = Site of continuous growth in sporophyte</p> Signup and view all the answers

    What structure in hornworts is responsible for producing spores?

    <p>Sporophyte</p> Signup and view all the answers

    The thallus of hornworts is typically a single cell thick.

    <p>False</p> Signup and view all the answers

    What term describes the small plants like liverwort and pennywort, which relate to the word 'wort' seen in hornwort?

    <p>small plant</p> Signup and view all the answers

    Hornworts produce gametes on the __________, where fertilization occurs.

    <p>thallus</p> Signup and view all the answers

    Match the following terms related to hornworts with their definitions:

    <p>Thallus = The flat green sheet of hornworts Rhizoids = Structures anchoring the thallus to the substrate Chloroplasts = Responsible for photosynthesis Mucilage = Substance produced at growing tips and some cavity structures</p> Signup and view all the answers

    Which genus of hornworts is known to have a strap-like thallus with a central midrib?

    <p>Dendroceros</p> Signup and view all the answers

    Hornworts produce numerous chloroplasts per cell, similar to mosses and liverworts.

    <p>False</p> Signup and view all the answers

    What is the term for the cavities within the thallus that can dry out, resulting in air-filled spaces?

    <p>mucilage cavities</p> Signup and view all the answers

    What role does Nostoc play in its relationship with hornworts?

    <p>Provides nitrogen to the hornwort</p> Signup and view all the answers

    Hornworts have scales on the undersides of their thalli.

    <p>False</p> Signup and view all the answers

    What characteristic shape do most hornwort sporophytes exhibit?

    <p>horn-like or needle-like</p> Signup and view all the answers

    The sporophyte of hornworts is a structure that contains a ______.

    <p>spore capsule</p> Signup and view all the answers

    Match the following genera with their characteristics:

    <p>Dendroceros = Nostoc cavities easily visible Notothylas = Short and stubby sporophytes Phaeoceros = Example of a hornwort Complex thallose liverworts = Differentiated cell layers in thallus</p> Signup and view all the answers

    How do hornwort sporophytes grow?

    <p>From points above their base</p> Signup and view all the answers

    The sporophyte in hornworts does not contain chlorophyll.

    <p>False</p> Signup and view all the answers

    What happens to sporophyte growth when the gametophyte suffers?

    <p>Sporophyte growth may stop.</p> Signup and view all the answers

    Where do the youngest cells of a sporophyte grow?

    <p>At the base</p> Signup and view all the answers

    Pseudo-elaters mature before the spores in a sporophyte.

    <p>False</p> Signup and view all the answers

    What happens to a sporophyte when it splits?

    <p>It releases spores over an extended period.</p> Signup and view all the answers

    Hornworts’ gametophytes create a plant body known as a ______.

    <p>thallus</p> Signup and view all the answers

    Match the terms with their correct descriptions regarding hornworts:

    <p>Gametophyte = Sexual generation producing thallus Sporophyte = Asexual generation producing spore capsule Antheridium = Male reproductive organ Archegonium = Female reproductive organ</p> Signup and view all the answers

    What is a notable feature of sporophytes from the genus Notothylas?

    <p>They may rupture irregularly or decay</p> Signup and view all the answers

    Hornwort gametophytes can vary in size from 1 to 2 centimeters in diameter.

    <p>True</p> Signup and view all the answers

    The two halves of a sporophyte usually remain joined at the very ______.

    <p>top</p> Signup and view all the answers

    Study Notes

    Hornwort Definition

    • Hornworts are flowerless, spore-producing bryophytes that are characterized by their tapering, horn-like or needle-like spore capsules.

    Hornwort Gametophyte

    • The gametophyte is a flat, green sheet called a thallus.
    • The thallus can be strap-like, branched, or grow in a rosette shape.
    • It has a thick, central midrib with thin lateral wings that are often wavy or ruffled.
    • The thallus is attached to the substrate by rhizoids, which are anchoring structures that are superficially root-like, but without the absorptive functions of true roots.
    • The thallus contains one to a few chloroplasts per cell, most commonly just one large chloroplast per cell.
    • Growing tips are covered by mucilage, which is produced by the surface cells.
    • Mucilage cavities are formed by the breakdown of many cells into mucilage, which can dry out, resulting in air-filled cavities.
    • The mucilage cavities are connected to the exterior through slime-pores or mucilage clefts.
    • Nostoc (a cyanobacterium) can enter the mucilage cavities through the slime-pores and form a symbiotic association with the hornwort.

    Hornwort Sporophyte

    • A single thallus produces many sporophytes.
    • The sporophyte is an erect, elongated, tapering, horn-like or needle-like structure.
    • It is typically several centimeters long, but can be over 10 centimeters in length.
    • The sporophyte is constantly growing from a point just above its base.
    • The youngest cells are near the base and the oldest are at the top.
    • The sporophyte contains chlorophyll and photosynthesizes, but still depends on the gametophyte for carbohydrates.
    • The sporophyte splits along its length (from the top down) to release the spores over an extended period.

    Hornwort Reproduction

    • Hornwort reproduction occurs in an alternation of generations, with a sexual generation (gametophyte) and an asexual generation (sporophyte).
    • The gametophyte produces male and female gametes (sperm and eggs) on the thallus, and a fertilized egg develops into a sporophyte.
    • The sporophyte produces spores, which germinate to begin the cycle again.
    • Hornworts can also reproduce vegetatively if the thallus is fragmented.

    How Hornworts Differ from Liverworts

    • Hornworts lack cellular oil bodies and have mucilage instead of air chambers.
    • Hornworts have a near-basal meristem, where cells continue to divide and grow during the sporophyte's life.
    • Hornworts have a tissue column on the capsule, called a columella.
    • Hornwort gametophytes have one large chloroplast in each cell, which contributes to their color and translucency.
    • Hornwort sporophytes exist even after the gametophyte dies.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 4: Hornworts PDF

    Description

    Discover the fascinating world of hornworts, flowerless bryophytes that have unique spore-producing structures. This quiz covers their defining characteristics, gametophyte structure, and adaptive features. Test your knowledge on this intriguing group of plants!

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser