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Ozone Damage to Ponderosa Pine: A Histological and Histochemical Appraisal

Lance S. Evans and Paul R. Miller
American Journal of Botany
Vol. 59, No. 3 (Mar., 1972), pp. 297-304
Stable URL: http://www.jstor.org/stable/2441432
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Ozone Damage to Ponderosa Pine: A Histological and Histochemical Appraisal
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Abstract

Histological and histochemical changes occurred in current-year needles of sensitive clonal selections of Pinus ponderosa Laws under natural summer growing conditions in the San Bernardino National Forest near Los Angeles, California due to fumigations with 0.45 ppm ozone for 12 hr/day. Within five days after the start of fumigation, chloroplasts and carbohydrate stain accumulated in the peripheral portions of mesophyll cells. Concurrently, the homogenous distribution of proteins and nucleic acids was disrupted. Succinate dehydrogenase was localized mostly in guard cells, resin duct epithelial cells, albuminous cells, and differentiating vascular tissues within unfumigated and fumigated leaves. Acid phosphatase activity increased within mesophyll cells during ozone exposure, but there was no association of acid phosphatase or ozone injury with stomata. Wall destruction occurred in mesophyll cells after appreciable intracellular damage. These histological and histochemical changes occurred within 5-7 days, but visual symptoms were not evident until 2-3 weeks after fumigation. It is thus possible to assay ozone damage very soon after exposure if no other external agents cause similar results.

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