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Original publisher: Albany, Calif.: U.S. Dept. of Agriculture, Forest Service, Pacific Southwest Research Station, [1998] OCLC Number: (OCoLC)228504428 Subject: Forest ecology -- Congresses. Excerpt: ... Session I Biochemical Reactions of Ozone in Plants Mudd 1. TRYPTOPHAN Figure 5 - Reaction of ozone NH NH with amino acids. O3 COCH CH CH CH 2 2 N O C NCHO C O H N-formylkynurenine 2. HISTIDINE NH NH O3 - CH CH OOCCH CH 2 2 N N + O O C C H H 2 aspartic acid 3. METHIONINE O NH NH O3 CH SCH CH CH CH SCH CH CH 2 2 3 2 2 3 O C O C methionine sulfoxide Foliar spray of ascorbic acid can prevent ozone damage to plants ( Freebairn 1957 ). Ascorbic acid in the apoplastic fluid of plant leaves has also been shown to be oxidized by ozone ( Luwe and others 1993 ). The reaction of ozone with ascorbic acid is stoichiometric, and the reaction is more rapid at pHs above the first pK ( pH 4.7 ) ( fig. 6 ) ( Giamalva and others 1985 ). The reactivity of ascorbic acid may also be caused by the cleavage of the double bond in the ring ( Chameides 1989 ), and the oxidation product may be an epoxide formed at the double bond ( Kanofsky and Sima 1991 ). There are precedents for both reactions. An examination of the product of oxidation of ascorbic acid by ozone using nuclear magnetic resonance, mass spectrometry, and enzymic re-reduction using DHA reductase ( fig. 7 ) has shown beyond doubt that the product is dehydroascorbic acid. Since dehydroascorbate reductase is common in plants, the oxidation of ascorbic acid by ozone in the apoplastic fluid is not a suicide-protection mechanism but rather a renewable form of defense. This defense does depend on the ability of the plant to take up DHA, re-reduce it in the cytoplasm and then export AA to the apoplastic fluid. O O Figure 6 - Reaction of ozone O O CHOH.CH OH CHOH.CH OH 2 2 with ascorbic acid. - O OH O3 O O dehydro ascorbic acid ascorbic acid Phenylpropenoids The phenylpropenoids are unique plant natural products. They have been rec
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Proceedings of the International Symposium on Air Pollution and Climate Change Effects on Forest Ecosystems, February 5-9, 1996, Riverside
Bokrecensioner » Proceedings of the International Symposium on Air Pollution and Climate Change Effects on Forest Ecosystems, February 5-9, 1996, Riverside
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