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Biochemistry and Cell Biology

Alterations in Growth and Water-Transport Processes in Fusiform Rust Galls of Pine, Determined by Magnetic Resonance Microscopy. Janet S. MacFall, School of the Environment, Duke University, Durham, NC 27706; Paula Spaine(2), Robert Doudrick(3), and G. A. Johnson(4). (2)USDA Forest Service, 320 Green St., Athens, GA 30602; (3)USDA Forest Service, So. For. Exp. Stn., Gulfport, MS 39505; (4)Department of Radiology, Duke University Medical Center, Durham, NC 27706. Phytopathology 84:288-293. Accepted for publication 7 December 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-288.

Galls on 10-mo- to 2-yr-old slash and loblolly pine seedlings inoculated with Cronartium quercuum f. sp. fusiforme were compared with healthy stems by magnetic resonance microscopy (MRM). After transpiration, high-resolution images (3558 m) of excised stem segments were acquired. MRM images showed a greater signal in the xylem of healthy stems than in galls, suggesting differing wood/water interactions. In 10-mo-old galled seedlings, the cambium and phloem were contiguous between healthy and galled regions. Water-transport disruption occurred in the xylem at the interface between galled and healthy regions, but in the center of the galls, secondary xylem appeared water-filled. At 2 yr of age, water transport was observed throughout the secondary xylem of a healthy stem but was completely impeded through the gall of a declining seedling. In contrast, a bright ring of conductive secondary xylem surrounded a dark, nonconductive center in the gall of a vigorous, 2-yr-old seedling. This study shows changes in anatomy and functional physiology in vivo with respect to water relations in fusiform rust galls on pine that are detectable by MRM.

Additional keywords: magnetic resonance imaging, MRI, plants.