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
Since wood wasnt invented, how were the plants able to stand up?
The leaves created structural support on the stem to help hold it up
Are lycophytes diploid?
yes, they are sporaphytes
What are strobili?
Spore cones produced either at the tips of vegetative shoots or on social fertile stems
What kind of spores to lycophytes produce?
one one kind, they are homosporous
-gametes are bisexual (n+n)
What type of fertilization do lycophytes go through?
aquatic
-swim from atheridium–> archegonium
In the Family Selaginellaceae what kind of spores are produced?
They are heterosporous
- microspores (develop in the microspores and are liberated)
- megaspores (depends on food reserves)
What is different about the family Isoetaceae?
- Instead of a stem the have basal swelling = corm
- ->specialized cambium which produces secondary growth
- also have CAM photosynthesis
What are the Lepidodendrales?
Tree lycopods (45m)
What are Equisetales?
horse tails
- stem dominant organ (has silica)
- Photosynthesizing scale like leaves
- Eustele
- Microphylls
What are Monilophytes?
plants with spores and true leaves
What kind of spores do Equisetales produce?
They are homosporous
-spores terminate to form bisexual gametophytes
What are Elaters and what are their purpose?
-Supposed to help with dispersion of spores, coiled around spores and can absorb water. When they do they uncoil releasing the spore
What is special about Psilatum?
Not primitively simplified
- no roots or leaves
- photosynthetic stems
- rhizoids
- endo with glomeromycota
- homosporous
What are ferns?
Broad leafed euphilophytes that reproduce by spores
- first group with “true leaves”
- no true wood
What kind of spores do ferns produce?
They are almost all homosporous
-all aquatic fertilization
What are Sori?
They are found on the back of the fern and what the spores develop in
Why are Azolla and Anabaena important?
They grow in rice paddies and have an association with cyanobacteria and fix N for them and the rice
Why are ferns evolutionarily important?
Not a lot of fungi eat them
