Maple Syrup in the Classroom by Pete Barnum

1
Lesson 3Sap Movement Physiology
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SAP Too Move or Not Too Move?

• Many factors effect sap movement during the syrup
  season.
• Freezing Nights and Warm Days
• Minimum and Maximum Temperature
• Length of Freeze and Thaw
• Availability of Soil Moisture
• Sap Sugar Concentration
• Barometric Pressure

3.1
3
The Details

• Freezing temperatures cause the gases in the tree
  (CO2 and O2) to contract causing a negative
  pressure (vacuum) in the tree.
• This allows more water (if available) to be
  absorbed by the roots.
• Warm temperatures cause the gases to expand
  creating a positive pressure in the tree.

3.2
4
The Details Cont.

• The taphole allows pressure to escape the tree in
  the form of gases and liquids (sap).
• This cycle continues throughout the season.
• Pressures of up to 50 PSI (pounds per square
  inch) have been recorded.

3.3