Lecture #8- Ancestral Vascular Plants Flashcards
What groups do the Embryophytes include?
The Bryophytes and the tracheophytes
-Thought to be monophyletic
What did the embryophytes evolve from?
Organism resembling coleochaete
What are Trilete Spores?
Spores that have a triangular scar on one surface form having been formed in a tetrad (meiosis)
How are triplets spores stuck together?
Stuck together in 4’s which are a product of meiosis
What are sieve elements?
They are the conducting cells of phloem
- Food transport
- Soft walls (aka not goof for fossils)
What are tracheary elements?
They are the conducting cells of xylem
- water transport
- tracheids and vessels
- rigid (good for fossils)
What helps prevent tracheary elements from collapsing?
- thichk walls with lignin
- spiral ridges
What is a lycophyte?
Sporic meiosis
What is a Stele?
Vascular elements which are located in the central cylinder
What is the most common Stele in plants?
Eustele
-had to evolve into the perfect one
What is Lignin?
- Complex natural polymer
- Ester and cross linked p-hydroxycinnamyl alcohol
Why is lignin decay resistant?
- Molecule is too large to fit into the active sites
2. Broken down products are toxic
Do all plants have the same amount of lignin?
No, all plants have a different proportion
How does lignin get broken down?
Enzyme creates a radical which physically breaks down the bonds
-has to do this because compound is to big t find into any enzymatic active site
Characteristics of Tracheids (xylem)?
- slender with a tapering end
- rigid or spiral like
- no holes through primary and secondary cell walls
- Came first
Characteristics of vessels?
-Tubular with ends containing perforations for continuous vertical connection between cells
-Found in anglos and gametophytes (130MYA)
-
What is the oldest known vascular plant?
Cooksonia (414-408MYA)
What are protracheophytes?
Not vascular plants
- cells resembles those of mosses
- diploid
- does have a vascular system
- non-living or fossils
Characteristics of cooksonia?
- Erect
- Terminal Sporangia
- Sporophytes
Characteristics of Rhynia?
- Protracheophyte
- Erect
- Photosynthetic branches (leaves weren’t invented)
- Stomata
- Elliptical sporangia
Characteristics of Zosterophyllophyta?
Found 408-370MYA
- lateral sporangia (opened up like purses)
- Mycorrhizal associations with Glomeromycota
- Rhyzoids
Characteristics of Lycophyta
- Microphylls and auxiliary sporangia
- have a protostele
- Rhizomes and true roots
What are microphylls?
Small leaves
in lycophyta where are the sporangia located?
In the armpit of the mycrophylls