EEB340 - Lecture 3

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18 Mar 2012

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Lecture 3: Origin of Land Plants: Evolution of Meristems and Parenchymatous Growth
Evolution of Parenchymatous Growth
Land Plant Cell Division
Microtubule Arrays
Land Plant Meristems
Anthocerophyta-to-seed Plants
- third important trait essential to survival on land Parenchymatous growth
- parenchymatous tissue produces volume in 3D multiple cells, not one big cell
- meristems: area of plants with fast-dividing cells (stem cells)
o perpetually dividing
o area from which all other cells derived
- surface area to volume ratio
o large organisms have low ratio (lots of volume to small surface area)
minimizes water loss
essential to terrestrial environment
- phragmoplast: array of microtubules involved in cell plate formation
o telophase and cytokinesis
o guide Golgi-derived vesicles to where new cell plate/wall being formed
o guide smooth ER to those regions (pectin-rich regions)
- plasmodesmata: critical in controlling plant growth and development
o control communication between cells
- meristem: region of undifferentiated, actively dividing cells
o source of cells for rest of plant
o if organism in vegetative stage, meristem is indeterminent (constantly
- hornworts have a single apical cell in their meristem
- hornworts have only a thalloid morphology
- liverworts have thalloid morphology or leafy morphology
o thalloid may have multiple meristems also leafy
o single apical cell
- mosses are leafy (in main, mostly photosynthetic form)
o single apical cell
- when 3D growth is initiated, instead of dividing periclinally, it divides at an angle
o each time new cell wall, plasmodesmata laid down
o this will lead to leafy structures of mosses
o when enters this developmental phase for parenchymatous growth, there is a
preprophase band (essential for this growth)
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