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Published byDarcy Daniels Modified over 8 years ago
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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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Alteration of Light Quality SOLAR RADIATION absorption transmission reflection rich in red light, low in far-red light lower in red light, richer in far-red light
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Phytochrome (P r & P fr ) P r - blue pigment (inactive) absorbs red light P r is converted to P fr by red light. P r P fr red light far-red light P fr - olive-green pigment (active) absorbs far-red light P fr is converted to P r by far-red light (or by darkness).
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Phytochrome Effect Active (P fr ) Inhibits stem and leaf elongation, resulting in smaller plants Promotes tillering, increasing shoot density Inactive (P r ) 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.
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