Transcript No Slide Title - Personal.psu.edu

Oak Hill Case
Atmospheric Problems
Shading
• PAR (red & blue light)
intensity are reduced by
shading.
• Light transmitted through
tree canopies comes
through at longer
wavelengths, including far
red light.
Shade Effects
QUANTITATIVE
reduced
photosynthetically
active radiation (PAR)
QUALITATIVE
photomorphogenetic
response due to
phytochrome
Light Quantity
30
Net Photosynthesis
25
20
15
10
5
0
0
100
200
300
400
500
-5
-10
PAR
600
700
800
900
1000
Light Quantity
30
Net Photosynthesis
25
20
15
10
Light compensation
point
5
0
0
100
200
300
400
500
-5
-10
PAR
600
700
800
900
1000
Light Quantity
30
Light saturation
point
Net Photosynthesis
25
20
15
10
5
0
0
100
200
300
400
500
-5
-10
PAR
600
700
800
900
1000
Light Quantity
30
Light saturation
point
Net Photosynthesis
25
20
15
10
Light compensation
point
5
0
0
100
200
300
400
500
-5
-10
PAR
600
700
800
900
1000
Alteration of Light Quality
rich in red light,
low in far-red light
SOLAR RADIATION
absorption
reflection
lower in red light,
richer in far-red light
transmission
Phytochrome (Pr & Pfr)
Pr - blue pigment (inactive)
• absorbs red light
• Pr is converted to Pfr by red
light.
red
light
Pr
Pfr - olive-green pigment (active)
• absorbs far-red light
• Pfr is converted to Pr by far-red light
(or by darkness).
Pfr
far-red
light
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
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.
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.
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.
Moisture
Moisture accumulation
within a turfgrass canopy
comes primarily from an
evaporative process,
called transpiration.
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.
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.
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.