LESSON 4: Seadless vascular plants Flashcards
What is the first fossil of a true vascular plant? What was their particularity?
Rhynia. They lacked leaves and roots.
What are rhizomes?
They support the plant body below ground and are horizontal modified stems that can penetrate a substrate and anchor the plant.
What are the 2 types of tissues that vascular plants contain?
Xylem and phloem
What is Xylem’s role?
To transport water and minerals (crude/rough sap) upwards.
How is done the transport of water and minerals upward in xylem?
It is a capillary action that relies on water’s adhesion (water + water), cohesion (water + tissue) and evaporation (at stomata).
What does phloem conduct?
It conducts products of photosynthesis (sugars) from leaves to roots and water + minerals from roots to leaves (upward and downward transport). Sugars and water form complex sap.
If the phloem does the same role as the xylem, why is the xylem still important?
Because it is much more efficient at conducting water.
Some cells of early land plants have specialized water-conducting cells. What do these cells don’t have that vascular plants have?
The cells did not provide mechanical strength.
What were later land plants able to synthesize?
Lignin, a polymer of phenylpropanoids.
Where is lignin deposited in a plant’s body? What does it provide for the plant?
It is deposited in cell walls, in the water-conducting cells. It provides support and rigidity to those tissues, allowing the plants to grow upright.
What is evapotranspiration?
It consists of water evaporating from plant leaves (high to low concentration mouvement)
In what 3 categories is the water used by plants repartied?
1) less than 1% is used for photosynthesis
2) less than 5% is used for growth
3) around 95% is evaporating
Why is there no evaporation inside the vessels of a vascular plant?
Because there is no air bubbles to serve as the energy of activation.
Where is the cambium and how does it grow?
Situated between the xylem (inner portion) and the phloem (outer portion), it grows inward and outward.
How is lignin though to have evolved?
Due to the high oxygen levels in the atmosphere around 430 mya which would have favored polymerization reaction.
Is lignin easy to degrade? What types of organisms can degrade it?
No it is very difficult to degrade. Only a few fungi and bacteria are able to.
Carboniferous forests were swampy places dominated by members of which phylum?
Lycophyta
Unlike Rhynia, what do lycophytes have?
True roots and true leaves
What type of leaves do lycophyta have?
Microphyll, a primitive leaf with only one vein.
In vascular plants, which alternation of generation cycle is dominant?
The sporophyte
What is the advantage of the sporophyte phase being diploid?
It has a backup copy of the DNAthay can continue to function normally even if one strand is damaged.
What are the 3 types of plants included in the phylum Pteophyta?
Ferns, whisk ferns and horsetails.
Why did the Carboniferous period continue for so long (150 my)?
Because of a moist climate over much of the planet and of the dominance of seedless vascular plants.
Where are confined most modern seedless vascular plants?
To wet or humid environments because they require external water for reproduction.
