Exam 4

Question 1

Challenges of Land for plants

Answer 1

1. water for photosynthesis (and reproduction)
2. drought stress
3. high irradiance (oxidative stress and UV damage)
4. severe cold (freezing) (water expands when cold)
5. anchoring to ground
6. building structures in air instead of water - things float in water

Question 2

Some green plant (viridiplantae) synapomorphies

Answer 2

1. chlorophyll a&b for photosynthesis
2. carotenoids as accessory pigments
3. double-membraned chloroplasts: origin of chloroplasts is an endosymbiotic event
4. sugars stored as starch
5. cell walls composed of cellulose and pectin (stick cell walls together)
6. phragmoblast - perpendicular microtubules relative to plane of cell division

Question 3

Chara

Answer 3

freshwater, living on land, 3D, haplontic life cycle, reproductive structures look like antheridium (sperm container) and archegonia (egg container)

Question 4

Zygnematophyceae

Answer 4

sister to land plants, freshwater, haploid, 2D growth, unicellular or filamentous, asexual reproduction & sexual reproduction through conjugation

• in stressful conditions, sexual reproduction happens via conjugation
• two haploid cells fuse (2N) and form a zygospore w tough outer coat made of sporopollenin
• when conditions are better, meiosis happens and haploid cells divide mitotically

Question 5

Spriogloea musicola

Answer 5

Presence of genes for response to stress
 - transcription factors
 - hormone signalling
 - cell wall remodeling
 - disease resistance
 - desiccation tolerance
Good candidate for ancestor to land plants - loaded with genetic info for the ability to survive on land

Question 6

Basidiomycota