Lychophytes Flashcards
What characteristic evolved to separate the Lychophytes from Zosterophyllophytes?
Microphylls
What are the three extant families of lychophytes?
Lycopodiaceae, Selaginellaceae, and Isoetes.
What is a microphyll and how does it relate to sporophylls?
Microphylls are small leaves and when fertile they bear spore-producing sporangia and termed sporophylls.
Which family in the Lycophytes is homosporous?
Lycopodiaceae
What are strobili?
A group of non-photosynthetic sporophylls grouped at the ends of aerial branches (cone-like).
Where does meiosis occur?
In the sporangium.
What happens to spores that are released from sporangium of Lycopodiaceae?
They germinate to become mature gametophytes bearing both archegonium and antheridia.
How does fertilization happen in Lycopodiaceae?
Mature antheridia release haploid bi-flagellate sperm that swim (requiring water) to the mature archegonium and fertilize the haploid egg, thus creating a zygote (diploid) cell.
Remember that the gametophyte is haploid and no meiosis is needed to produce sperm and egg. That is through mitosis.
What are the five components that make up the developing embryos of Lycopodiaceae?
- Foot
- Root
- First leaf
- Shoot apex
- Suspensor
What is a suspensor?
It serves to thrust the developing embryo deep within the developing tissue of the female gametophyte in some species of Selaginella, but is inactive in all of Lycopodiaceae and some other species of Selaginella.
What is heterospory?
Heterosporous plants produce 2 types of spores, sporangium, and sporophylls.
Megaspores are produced in megasporangium and located on megasporophylls.
Microspores are produced in microsporangium and are located on microphylls.
What is the difference between microspores and megaspores?
Microspores contain a microgametophyte that produces sperm cells via mitosis, while megaspores produce a megagametophyte bearing an archegonium. The archegonium is then fertilized by the sperm produced by the microspores.
What is a ligule and which families have them?
A ligule is a small, scale-like outgrowth. It is located near the base of the upper-surface of each microphyll and sporophyll in Selaginellaceae and just above the sporangium of each sporophyll in Isoetes.
