How Plants Colonized Land
A. "Adaptation to Land" Review
What are the adaptations found in terrestrial animals? Would similar adaptations be found in plants?
B. What is the phylogeny of land plants?
Bryophytes
Pteridophytes
Gymnosperms
Angiosperms
closest relatives are (Charophycean) green algae
C. What traits do these green algae and plants have in common?
-autotrophs: chlorophyll "a" and "b"
cell walls: phragmoplast, cellulose synthesis
D. What derived characters are unique to terrestrial plants?
1. apical meristems
leaves
stems
roots
2. 'Protected" embryos
-embryophyte
examples:
-liverwort gametangia: archegonia, antheridia
-flowering plant: flower, ovule, seed
3. Alternation of Generations
-What are the generations that alternate?
gametophyte
sporophyte
Bryophyte (gametophyte conspicuous)
Pteridophyte, Gymnosperm, Angiosperm (sporophyte conspicuous)
4. "Protected" spores
-sporopollenin
sporangia
examples:
gymnosperm
E. Other Adaptations Common in Terrestrial Plants
1. cuticle
waxy coating
cuticle on upper surface of oak leaf
stomates (again)
2. Water Transport System
xylem
phloem
The upward movement of water through the xylem of a plant is driven by differences in water potential
What is water potential?
How do differences in water potential determine the direction of water flow?
What is the evidence that water in the xylem is under tension?
The movement of solutes in phloem is driven by a bulk flow mechanism
What causes bulk flow?
3. Secondary Compounds
-Plants produce a variety of chemicals not related to primary metabolism
-What are the roles of these secondary compounds for the plant? What other uses do these compounds have?
Anthocyanins as "sunscreens" in Black Jack Oak
