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Biologic Markers of Air-Pollution Stress and Damage in Forests (1989) / Chapter Skim
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Biochemical/Cell-Tissue Session
Pages 245-246

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From page 245...
... Nitrate reductase activity also can be measured in the field and may be a useful marker for trees that are impacted by nitrogen pollution, but extensive characterization of diurnal and seasonal variation in foliar NR activity is an important prerequisite. THE NITROGEN HYPOTHESIS OF FOREST DECLINE One of the hypotheses that has been put forth to explain forest decline in eastern North America and western Europe is the so-called "nitrogen hypothesis." This hypothesis states in part that elevated levels of nitrogen deposition in a form available for direct foliar uptake by tree canopies (e.g., HNO3 vapor, NO, N02)
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From page 246...
... , nitrite, urea, and certain amino acids (Haynes and Goh 1978~. The activity of NR is influenced by a number of other environmental factors, including light, temperature, drought, and time of day, and physiological factors, such as hormones, carbohydrates, leaf water potential, and tissue age (Beevers and Hageman 1983~.
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Key Terms

  • nitrogen oxides
  • nitrogen hypothesis
  • forest decline
  • appropriate marker
  • nitrogen deposition

  • biological marker
  • atmospheric deposition
  • red spruce
  • spruce foliage
  • laboratory studies

  • physiological imbalances
  • enzyme nitrate
  • gaseous nitrogen
  • hypothesis states
  • explain forest

  • manipulative laboratory
  • spruce seedlings
  • logical sequence
  • processes required
  • elevation red

  • acid deposition
  • growth processes
  • predisposing stress
  • normal nutrient
  • research sponsored

  • picea reubens
  • efficient approach
  • valuable biological
  • reductase activity
  • eastern north


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