EEB340H1 Lecture : EEB340 - Lecture 5
18 Mar 2012
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Document Summary
Water conducting cells tracheary element in xylem. Suggested that water conduction was secondary to support. Water must move through pits to move from tracheid to tracheid. Water moves through perforation plates in vessel elements minimizes resistance thalloid liverworts and hornworts would create carpets of photosynthetic cells eventually run out of room and are competing: only place to grow is up. Branchings became dichotomous equal forks being developed: how liverworts colonize environment. Silurian: can get support for this height from epidermal cells (hoop like support) and turgor from parenchyma cells: beyond 0. 48 meters need other structures. Plants used upright structure to decrease water loss and maximize sunlight capture (without leaves) In first land plants, secondary wall would not be as developed, but importantly would have contained ligning. Rynia (0. 5m tall) above 0. 48m so developed some support tissue. Psilophyton (1m tall) central core of support tissue (cells contain ligning: hypodermal sterome cells with very thick walls.
