Oak Hill Case

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Oak Hill Case

• Atmospheric Problems

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Shading

• PAR (red blue light) intensity are reduced by
  shading.
• Light transmitted through tree canopies comes
  through at longer wavelengths, including far red
  light.

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Shade Effects

• QUANTITATIVE
• reduced photosynthetically active radiation (PAR)

• QUALITATIVE
• photomorphogenetic response due to phytochrome

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Light Quantity
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Light Quantity
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Light Quantity
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Light Quantity
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Alteration of Light Quality
SOLAR RADIATION
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Phytochrome (Pr Pfr)

• Pr - blue pigment (inactive)
• absorbs red light
• Pr is converted to Pfr by red light.

• Pfr - olive-green pigment (active)
• absorbs far-red light
• Pfr is converted to Pr by far-red light
• (or by darkness).

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Phytochrome Effect

• Active (Pfr)
• Inhibits stem and leaf elongation, resulting in
  smaller plants
• Promotes tillering, increasing shoot density

• Inactive (Pr)
• Promotes stem and leaf elongation, resulting in
  larger plants
• Inhibits tillering, reducing shoot density

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Other Shade Effects

• Thinner leaves and cuticles
• Shallower rooting
• Reduced carbohydrate reserves
• A shade turf is thus more delicate and less
  tolerant of wear, disease, and environmental
  stresses.

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Poor Air Circulation

• Closely planted trees and shrubs restrict air
  flow, resulting in a warmer, more humid
  microenvironment.
• As a consequence, disease pressure is greater.

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Wind Effect

• Wind moves parcels of air from the turf and
  incorporates them into the larger volume of air
  above it.
• Thus, the accumulation of heat and humidity are
  dissipated.

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Moisture

• Moisture accumulation within a turfgrass canopy
  comes primarily from an evaporative process,
  called transpiration.

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Transpiration

• Water is absorbed by roots, translocates upward,
  and accumulates as films of moisture on internal
  leaf cells.
• Water films evaporate and exist the leaf through
  pores, called stomates.

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Boundary Layer

• Water vapor exiting the stomates accumulates in a
  layer of humid air immediately around the leaf.
• With the development of boundary layers around
  all leaves, the environment of the turfgrass
  canopy can become quite humid.

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Wind Effect

• With moderate air movement across the turf,
  however, the humidity of this environment can be
  substantially reduced.
• And the potential for disease is proportionately
  reduced.