Biologic Markers of Air-Pollution Stress and Damage in Forests (1989) / Chapter Skim
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Co-occurring Stress: Drought
Co-occurring Stress: Drought
Pages 357-363
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From page 357... ...
This paper is The mediating factor most often influencing the growth response of trees to drought is turgor pressure, because it is the force causing plastic enlargement of cell walls and vegetative growth (Hsiao et al., 1976; Bradford and Hsiao, 1982; Tyree and Jarvis, 1982~. High turgor pressure is needed to cause sufficient enlargement for cells to reach the critical size for division (Doley and Leyton, 1968~.
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From page 358... ...
During primary growth, cell division at the apical meristem and the subsequent elongation of newly formed cells results in the formation of leaf bud primordia. Water deficits may affect the formation of leaf buds and/or the subsequent elongation of preformed leaf buds in conifers.
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From page 359... ...
Environmental causes of embolism include water stress and winter freezing; potential consequences include reduction of growth and dieback. Water stress leads to embolism via the process of "cavitation," the breaking of water continuity in xylem conduits subject to negative pressures arising from static effects (dry or frozen soil)
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From page 360... ...
of surviving minor branches due to leaf loss from dead shoots. The model predicted that all species operate near the point of catastrophic xylem failure due to dynamic water stress.
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From page 361... ...
However, many of the symptoms of drought stress might be confused with pollution induced decline syndromes, e.g., reduced leaf size, reduced leaf area, reduced bole diameter growth, reduced shoot elongation and stem dieback. For this reason it may be advisable to measure water relations parameters before ascribing a cause-and-effect relationship between decline and air pollution levels.
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From page 362... ...
1982. Correlation between changes in photosynthetic activity and changes in total protoplast volume in leaf tissue from hygro-, meso-, and xerophytes under osmotic stress.
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From page 363... ...
However, many of the symptoms of drought stress might be confused with pollution induced decline syndromes, e.g., reduced leaf size, reduced leaf area, reduced bole diameter growth, reduced shoot elongation and stem dieback. For this reason it may be advisable to measure water relations parameters before ascribing a cause-and-effect relationship between decline and air pollution levels.
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