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EEB340 - Lecture 4

Ecology & Evolutionary Biology
Course Code
Rowan Sage

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Lecture 4: Origin of Land Plants: Evolution of Meristems and Parenchymatous Growth
Evolution of Parenchymatous Tissue
Growth/Meristems of Green Algal Ancestors
- single apical cell divisions always anticlinal to the surface (never parallel)
Seedless Vascular Plants
- Pterophyta Ferns, Equisitium, Psilotum
- Lycophyta (club mosses)
- Gametophyte is dominant form for hornworts, liverworts, and mosses
- Sporophyte dominant for seedless vascular plants and onwards
- Lycopodium
o Epidermis from all periclinal divisions
o Actively diving cells (anticinally or periclinally) make up the meristem
- Sincle apical cell increase in plasmodesmata (lots of communication)
- Multiple Initials decrease in plasmodesmata (can spread out information over
larger/broader area)
- No preprophase band in green algae
o Autapomorphy of land plants that allows parenchymatous growth
- Cleavage furrowing
o Different from land plants, where in to out
o No plasmodesmata
o No phragmoplast
o No preprophase band
o Seem to be some microtubues involved
- Algae can excrete the glycolate into the environment (easy because are one cell
layer thick) plants with parenchymatous growth cannot do this (instead excrete
into peroxisome)
- This relationship among the organelles and the presence of GDC seems to have
evolved and been co-opted by Choleocheatales and Charales essential to
evolution of land plants
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