Lecture 15 – The Origin and Evolution of Plants“Green Algae” & Land Plants – Synapomorphies (shared characteristics)- Chlorophylls a & b- Cellulose (poly-D-glucose, B-glycosidic bonds) cell walls- Starch (poly-D-glucose, a-glycosidic bonds) energy reserveCandidates for closest algal relatives of land plants- Coleochaetales (coleochaeates) or …- Charales (stoneworts)- Which one?o Charales (stoneworts) closest toland plantsPlants invaded land ~ 475 mya rapidlyradiated!Two big themes of land plant evolution- Watero How to get ito How to keep ito How to move it around- Sexo Dominance of sporophyte vs.gametophyteo Strategies for dispersalLand Plants (Non-vascular plants)- Nonvascular plants do not have vascular tissue to conduct water and provide supporto Shorto No rootso Grow only when damp (but often tolerate intermittent dryness)o Waxy cuticles and pores (+ guard cells in all but liverworts)Land Plants (Seedless vascular plants)- Seedless vascular plants have vascular tissueo Vascular tissue composed of tracheidso Have true (but limited) rootso Waxy cuticle, stomata (= pore+ guard cells)o Tend to live in damp placeso Most small, but some huge(e.g. tree ferns)Land Plants (Seed Plants)- Gymnospermso Vascular tissue of tracheids &vessel elements in somegroupso Have highly developed roots(can be bigger than shoot)o Waxy cuticle, stomatao True leaveso Some have wood: mix of tracheids + vessel elements in xylemo Can live in very dry or rocky placeso Woody species can be
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