THE SPECIAL BIOLOGY OF TREES

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THE SPECIAL BIOLOGY OF TREES

• Basic statement Trees carry out the same life
  functions as smaller plants. However, their large
  size and long-life spans make these functions
  more challenging than for many other plants.

Identify three challenges faced by trees and
not herbs, for example. 1. 2. 3.
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Special biology cont.

• Trees have many parts that require
  "communication" (among buds, among branches,
  between roots and shoots).
• Trees can move water from the soil to more than
  100 meters or 330 feet above the ground without
  expending energy (maximum height is over 400
  feet).
• Trees must endure large environmental
  fluctuations over widely different time and space
  scales. They use a combination of phenotypic and
  genotypic solutions to this challenge.
• Trees reach massive sizes,
• Trees live a very long time.

How might this communication work?
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Special Biology - cont.

• Illustrations

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Challenges of Large Size ??

• What are the problems?

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Challenges of Large Size Growth

• How to grow? Difference between plant and animals
  (meristems or perpetually embryonic tissue)
• Modules

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Challenges of Large Size Growth

• Need girth
• Need transport
• Need protection

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Challenges of Large Size Water

• From roots, through stem, out of leaves- often
  moves 100-300 ft.
• What "drives" this movement?
• water not pumped from below
• evaporation from leaves "pulls" water through
  stem
• nutrients are in solution move passively with
  water

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Challenges of Large Size Coordination of parts

• Trees are made up of many different parts that
  are interdependent
• Chemical Signals Role of growth, environment and
  stress
• Carbon signals
• Physical signals
• Wind
• Cavitation

What are the coordination issues?
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Challenges of Large Size Repair

• Over their life time, trees are invariably
  damaged (fire, wind, insect) - must deal with
  damage
• Compartmentalization
• Modular growth addition of parts by growth of
  new parts from buds
• Example with Douglas-fir
• Example with mountain hemlock
• Totipotency when "shocked" meristematic tissue
  can produce different specialized tissue

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Challenges of Large Size Repair
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Challenges of Large Size Orderly Senescence

• Why do plant parts have to senesce and die?
• How would you organize plant parts to senesce and
  die?
• Priorities?
• Recovery?

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Challenges

• Are presented in time
• Are presented in space
• Phenotypic plasticity
• Genotypic mechanisms