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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
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2441432
Page Count: 8
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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.
American Journal of Botany © 1972 Botanical Society of America, Inc.